Why positive ground was used on old cars, trucks and tractors
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- Опубликовано: 26 июл 2024
- In this video, I answer the question of why positive ground was used on old cars, trucks and tractors. Furthermore, I speculate on why negative ground is used today. At the end of the video, I answer some questions and offer some helpful hints. And, you don't need a degree in Electrical Engineering to follow along.
For those of you who do not want to watch the entire video, I attempt to get to the answer immediately right at the beginning of the video. Then, I go into a deeper dive. 
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Thank you. I had the proble of comprehending the positive ground setup on the IH I am attempting to restore. . Hours of RUclips watching didn't get my light bulb go on over my head. It just took the right person to explain it the way I could comprehend it. Definitely will lean up every connection and thanks again for your knowledge.
Hi Ken. Thank you for watching and commenting. Yes, clean up every connection on the generator. All the way to the block. Then, if your H is old, the generator field is grounded through the cover on the electrical box! Yeah, a bad design from IH. If the generator is not charging, this is very often the problem. On my H, I ran a braided ground wire from the L,H,D,B switch to ground. A vast improvement. My H is 6 Volt Positive ground and its staying that way. It always charges and starts.
years ago in high school auto shop class i was summoned to explain the ignition circuit
from a perfectly good daydream. about halfway through my answer i got a notion to improve this boring single coil system and described a system with a coil on every cylinder. the teacher was not amused with my"foolishness" and i was rewarded with an after school detention. neither one of us knew this would become a reality one day. your video reminded me of that day when i was thinking outside the box. thanks for sparking my memory.
Hi EMF. That is such a cool story! I laughed when you got a detention for thinking outside the box. ha ha Oh, those were the days!
Now, imagine had you said: And, no carburetor or distributor either. That would have been worth a suspension from school for 3 days. ha ha Just like getting caught smoking in the welding booth.
I will admit, when I was young, and in school, I needed that explanation you gave. I always thought the spark plug fired when the breaker points closed. It took me into college before I understood that the spark happens when the points open.
My P71 4.6 liter Crown Victoria Interceptor has a coil for each cylinder. I drove Taxi Cab in Detroit for 7 years. There the toughest, most durable cars on the road today and I'll stand by every word I just said " TOUGHEST "
@@bryanh1944FBH I figured this out indirectly when I was a kid and playing with a big solenoid coil picking up nails and things and using it for an electromagnet. I was curious to the fact that if I disconnected the coil, I would get much bigger sparks than just shorting out the battery intermittently with a short piece of wire. I was puzzled and thinking why does the coil appear to "pull" more power out of the battery than a dead short? Well, I was holding both wires and I discovered what happens when the current flow stops! I got a hell of a shock from holding one lead in the left hand, and the other lead in the right hand and when the field collapsed in the coil, it went right through both arms through my chest and sat me on my ass. And here I was thinking how can playing with a 6 volt battery possibly give me a worse shock than sticking my finger in a light bulb socket... LOL. I wasn't an ignition coil, but the voltage spike was probably around 200 volts, nowhere near an ignition coil, but probably a lot more current, and 200 volts hurts...
Your teacher wasn't such a bright spark.. 🙄😄
a lot of old engines had a buzz coil for each cylinder before the distributor was invented the Ford Model T is an example.Their sparks went every which way.
As a young 12 volt tech, I ran into some old big rigs w/ 12v chassis. This is back when radios were mounted through their shafts. I quickly discovered that the nylon antenna bushings for cb radios fit these shafts perfectly. With that and the amazing amount of room in these dashes, I developed a reputation for being able to install regular negative ground radios to work reliably in those old trucks. Lost count of how many "conversions" I did. Found memories of a 30+ year 12 volt tech.
You probably just missed out on the 6 volt systems.
Yeah I discovered the hard way ,bk 85 ish I bought the old man a high power Alpine system for his truck and decided to surprise him and pull off a midnight install so when he headed out at 3am he be bumpin ,🤣 at 3am the cab still smelled like smoke ,it was a long week
@@tstricklin4808 it was the thought the counted 😂
Yes I smoked a CB radio a time or two before I started putting a 2 amp fuse in both lines.
I have a 1947 John Deere B and could not for life of me understand why positive/ground. Now I understand! No one could effectively explain this as you have. Thank you.
Hi Marine 72! Thank you for the comment. You are welcome.
I agree no one could explain as done here, and what exactly is the explanation other than saying observations in an authoritative tone? How can saying electricity travels from one pole to another without mentioning electron theory vs hole theory ever, on God's green earth, be considered an explanation? With all due respect, that is.
I was a electronics teacher at a community college for 20 years and every thing you said was 100% true. Thanks for presenting it so well to many viewers.
Hi Martin! Thank you for the very nice comment. I appreciate it greatly. Enjoy your day.
Great Video! I am an old farm boy and grew up with I/H Farmalls. Also a multi ticketed mechanic with one being ag-mechanic I did notice one thing, no matter whether positive or negative ground , magneto or point ignition ,when the engine is running and you accidental touch a bad plug wire those electrons have quite a punch. Put a saint into swear mode.
Hi Murray! Yes, those electrons can pack a punch. ha ha I too have been shocked by ignition coils. Never a nice experience.
Used to work as a mechanic with a fellow who tested plug wires by spraying them with water and running his hands over them. Would have knocked me to the floor!
@@tedrice1026 Hi Ted. Interesting! When I worked in the field, I saw electricians who would tough 110 Volt circuits to see if they were hot, or not. And, they were all seasoned professionals too!
The one thing that I agree with on this video is that there is no music and that you do not feel the need to shout. Well done for that.
Thank you Billy.
I liked how when cars had steel bumpers you could touch bumpers and just use one cable to jump the dead one off (if they both had the same ground system).
Although, many cars back then also had a manual trans, so just a little coast and pop could get you there too
Now that is old school technology. When you grew up how many dinosaurs were roaming the streets? I never considered that in the era when old cars were totally grounded into metal bumpers
@@ben91069 The same amount of dinosaurs as now, only the air and water were cleaner
Bumpers together, and a piece of coat hanger wire. At 3 am, on a back road in Alabama, drizzling rain...who cares if it burns your hand a little...👍👍
@@nickv1008 LOL, been there😏
That was particularly useful when the batteries were on different sides of the car. Join the red and black together, just make sure they don't short to any bodywork. Automatics are still rare this side of the pond, so bump start and push start are still available. I hate to imagine how many times I used all three methods before I got my first reliable car. Driving used to be an adventure!
Retired EE. I was taught that positive to negative current was "conventional" current and negative to positive was "real" current, as an homage to Franklin and others.
EE here as well. I believe that virtually all of us think in terms of conventional current flow as opposed to "real" current. I find it MUCH easier, generally speaking.
I mostly see the need to know this in vacume tube guitar amps.
@@don_cc123 That works well only until you hit a semiconductor...
I think in both terms (electrically bilingual, LOL) [or is it ambidextrous???]
very good description of the automotive electrical, it explains why it's always the negative cable that gets hot when there's a bad connection.
When I went to electronics school we were taught that current flowed from + to - and electrons flowed from - to +. Works fine as long as you don't mix them up.
What magic is this?
Ben Franklin started the + current flow myth but he was fooled by ionic plating of metal in a battery. Later we discovered electrons were actually carrying the current. Today electronic techicians in the military and tech schools are taught electron flow and 'left hand rule' in electromagnetic polarity determination. Classical engineering texts still cling to the 'positive current' flow rules and diodes and transistors still have 'arrows' pointing in the direction of 'positive current' flow and they have texts with 'right hand rule' for electromagnetic polarity determination. In fact it doesn't matter as long as you are consistent in using either one or the other in solving circuit problems.
+ to - is conventional current and is taught to engineers. - to + is electron flow and is taught to technicians. It just adds to the fun when the two try to talk to each other.
+(potential voltage) -( ground/meutral) refers to polarity; +(cathode) -(anode) is a different perspective remember/ study your chemistry. You will not have a vivid understanding on the Laws of electricity if you omit the science part of it.
@Kelly Harbeson ...hole flow was always just for math.
I have four tractors three of which are 6 volt positive ground and I always wondered why. This video CLEARLY explained it. Thank-you.
Hi Beirne Farm. Thank you. I would love to come to your farm and look at your tractors!
Hi. Thank you for watching. Its been a while now since your comment. I hope you have five tractors by now! ha ha
Thanks..... I worked with super sensitive electronics in my career and corrected noisy circuits by revising PCBs ground buss thinking of current flow within them. Your discussion is so spot on.
What does it mean to revise pcb ground buss? I assume pcb means printed circuit board, and noisy? Like metal film resistor vs carbon? Or spurious radiation?
Thank you. I appreciate you watching the video.
Very helpful ..I watched just to under stand positive ground on a 53 mercury monteray .all original...now I understand...no wonder that car has no rust...71 years old...thank you Brian..
Great educational video! I was also in the crowd of people who thought electrons ran from positive to negative, I didn't even know you could have a positive ground. I'm enjoying the content, keep up the good work!
@sourand jaded Tesla coils produce AC. The arcs come from whatever is pointiest. If the electrode at the top of the Tesla coil is a round ball, then the arcs (both positive and negative) will come from each edge, corner, point, or blade of grass around.
hole flow is the flow of positive particle in electronics theory when one electron leaves this spot there is a hole that will move to the next created spot of an electron ergo hole flow
@sourand jaded Not a single crt TV set i know has grounded screen. Grounding the screen would require the cathode side of crt to be at said 20 kV negative. That means, the whole circuit must've be isolated from that high voltage, including all potentiometers, antenna input, speaker/headphones output, mains supply and so on. You can get away with that in some small oscilloscope, where the high voltage would be at 1 kV, but definitively not with TV receiver having up 40 kV. And yes, they do zap, but not stronger than static in clothes. And they attracts a lot of dust which you have to clean with a dry cloth, otherwise you risk receiving serious shock.
@@leopoldpoppenberger8692 Just like 'conventional' current, 'hole flow' is just a conceptual aid. Holes are just spots where there could be an electron, but there isn't, in the same way a vacuum is just a place where there could be matter, but there isn't, not even gas. Holes don't actually move. When an electron moves in the lattice a hole 'appears' where the electron came from and the hole the electron moved into 'disappears' but in another way it doesn't, it just isn't empty anymore. It's still a place where an electron can be, but there is.
@sourand jaded But the cathode is NOT several kV in relation to the grounded frame, for reason I mentioned already. The cathode and Wehnelt cylinder are a part of vision amplifier circuit, which has to operate with about 100 V amplitude and frequency ranging from DC do several MHz. There is no way to shift that signal by potential of tens of kV below ground. The anode side doesn't have any signal on it. It's just DC provided by flyback transformer, filtrated by capacitor made of inner and outer layers of coating on glass of CRT, at the funnel part of it. Maybe that coating made you confused but the anode inside the CRT is very much positive in relation do the ground.
You are correct about the spark. I trained over 50 years ago and work on more LUCAS generator and regulator systems than anything else. It was always explained that it is positive ground, negative spark. LUCAS coils were wound for positive ground and for the transformer effect. I had a problem on a forklift that had a positive earthed alternator. It was wired wrong and the spark was coming up the spark plug instead of going down. After diagnosis and rewiring the the coil and reversing the battery everything worked correctly.
Thank you for watching and commenting. Thumbs up! You are exactly right. I like the experience you have! And, both you and I understand the difference between "the spark was coming up the spark plug instead of going down". That makes all the difference in the world.
I've often wondered about this topic. Thanks for the enlightenment. 👍👍
That's a beautiful lamp too.
Negative ground is more convenient for vacuum tube radios. The cathode being biased close to ground level with electronics boiling off of it to the anode. With the relative high voltage being isolated, things at ground level are safer to touch.
I vaguely remember reading a few decades ago, that the primary reason for switching to a negative ground at least on automobiles had something to do with car radios becoming more common. I can't remember exactly why or where I read it? Perhaps it was an article in "American Heritage Invention & Technology" magazine? I don't think, that it was an issue concerning interference, but maybe something to do with having a better ground plane for the antenna? I wish; I could remember, but now that you mention it, maybe whatever I read did say, that the risk of getting hit with 90 vdc plate voltage was the issue, and I'm conflating a different article when it comes to a ground plane? At least, I may have been right, that it had mostly to do with the radio. Am I mis-remembering? Of course tractors, when they switched to negative ground, few if any had radios, but I figured, that they changed to be consistent with cars, to avoid confusion.
You are absolutely wrong. The positive spark is connected to the electrode and the ground is made through the block and the threads. The electrons jump to the electrode. The way you are explaining this suggests the body of the car has the opposite ground than the engine.
@@sparky6086 I think you've got a point here.
The original vacuum tube radios have nothing to do with this. The anodes of the tubes are not supplied directly from the 6V or 12V supply voltage. They used +200V which was produced from a vibrator and transformer. That can be designed to operate from positive or negative ground.
However it did become an issue with the latest vacuum tube radios shortly after 12V became common. These radio used 12V on the tube anodes directly from the input, so it did have to be plus 12V (negative ground.).
@@danecantwell22 I first thought the same thing, but I researched what he said and it turns out he is correct. Sparkplugs do want to be positive ground. The coils secondary and primary are isolated from each other. The primary is excited by the cars electrical system and the secondary is charged by transformer action. The secondary produce a large voltage across the spark plug gap in the range 5,000 to 20,000 volts, so this high voltage is going to arch to anything close enough to it. It makes little difference if the spark archs to an electrode at 12 volts or one at 0 volts.
Loved this video, and I just bought an old Fergesun tractor having a positve ground. I think I will try to keep it positive ground for the benefit that it causes less corrosion, which is electrolysis between the metal and the air. Phone companies noted that positive ground worked better and less corrisive than negative ground systems in the old days before plastic insulations. There is a third charge which affects the corrision and that is the charge of the air.
It actually goes all the way back to the early telegraph networks.
yes
Hi Ben! Thank you. I agree with you. And, keep the old tractor + ground.
@@bryanh1944FBH I will but I want to make it a 12V positive ground so I can used solid state ignition components instead of points and a higher voltage coil for easy starting in cold weather
Send me more info
From a 43 year electrician. Excellent video. Great job. I really enjoyed it.
Thank you. I appreciate the comment!
I am in a rabbit hole of posative ground at the minute.
The " distributor is a ground" line really hit it home for me.
Thanks for the videos. You know your stuff.
Hi S8 Mury. Yes, the body of the distributor MUST make good contact with the engine block or the ignition system will not work! This has happened to me. The aluminum housing of the distributor gets a layer of oxidation on it and good electrical contact is gone. Especially if its only 6 Volt to start with!
My friend had a 67 MGB . He took it to two different mechanics that couldn't figure out why it wouldn't start. I told him to check the braided straps that went from the transmission to the frame and the rear end to the frame and the engine to the frame. He didn't believe me. I let him flail at it for a week. I came over one afternoon and said, George, let me try something. I hooked all of the ground straps back up,after cleaning them and the surfaces, and guess what. Yah it started right up. It's weird how people who were struggling for an answer wouldn't believe me after answering their question. Went through 30 years of maintenance with people like that. 👍
Yes, in all my old positive earth vehicles corrosion at the point of earth was a big problem with corrosion spreading out from that point like the plague. Since we have has negative earth systems body corrosion due to electrical flow seems to be a thing of the past. The days of positive earth, dynamoes and voltage control boxes gave rise to nightmares.....and a lot of vehicle fires...never mess around with a voltage control box unless you really know what you're doing.
I am surprised that he didn't destroy his control cables, choke etc. The starter motor would try to earth through these cables. I had that problem some years ago when an earth strap was left off.
Outstanding video! Content and presentation is very professional! Thank You Sir!
Hi David. Thank you for the comment. I too am learning from all the comments. In time, I would like to do this over and add even more.
I attended California Maritime Academy during the mid 70s as an engineering student. We took 5 classes of electricity. We were taught electron flow as well as conventional flow in DC circuits. The teacher really messed with our minds in lab class by intentionally confusing the two flows. We put together kit DC motors and were grilled on which direction that they would turn before closing the knife switch. I have collected WWII Dodge army trucks and post war Power Wagons. Most of the WWII trucks were 6 volt positive ground but the radio trucks were all 12volt negative ground, because of the radio equipment was 12 volt negative ground. The 6 volt generators have labels which are red in color, the 12 volt generators have green colored labels. I have always assumed that because the manufacturing was set up during WWII, it was easy to switch to 12 volt negative ground 10 years later. I have a bunch of 2N and 8N tractors with a "permanent" implement attached to each one. Most of the tractors are still 6 volt, but the one with the snow blade is 12 volt because the engine turns over better in the cold, especially when the tractor is being somewhat abused and routinely stalled by pushing too much snow around. The Ford 6 volt generators have no voltage regulators, just a cut out and a movable third brush. This will slightly over charge a battery, reducing the life. A one wire GM alternator will extend the battery life to 6 years. Also worn out 12 volt batteries will still start lower compression engines where the six volt battery MUST be in perfect condition. I can jump other 12volt vehicles with that tractor too. I have a Model A with a reworked 6 volt positive ground GM alternator, the 6 v battery will last for 5 years.
Hi Steve. Thank you for watching and commenting. Very interesting comments. An education that has you determining the direction of rotation before electricity is applied is a very thorough education indeed. We just started our 6 Volt H last weekend after sitting all winter. One crank and it was running. Take it a bit easier on that snow pusher! ha ha
My first car was a 63 MG Midget, and it was positive ground. It also had an old 'lorry' transmission with a non synchro 1st gear. It was basically a sporty, drop-top, tractor!
My 65 MGB was also positive ground. In fact, all English made cars were positive ground. (non synchro 1st gear is normal in them days. It was also termed "Bull-low" as it pulled like a "bull", as it was all torque. Which is why many started off in second gear instead as it was the most useful gear speed wise and you did not STALL IT.
You just had to remember that when connecting jumper cables. Connect directly to the battery. Some early Japanese cars were also positive ground. Maybe Datsun(Nissan)?
. You must also remember to check the jumper cables as a joke someone swapped the red clamp with the black clamp. Not a "Factory error" as there are thousands of jumper cables produced so that is a MAJOR ERROR. I got a set of jumpers given to me to jump someone's Toyota at college. So I hooked up the Toy and then to my VW without checking to see if the clamps were the correct color as it was a paired unit. "I ASSUMED IT WAS RIGHT". When I hooked up to my battery there was a lot of sparks(more than normal) The Toy would not crank the starter motor. Weird. I took off the jumper cables and then noticed that the black was red at the other end. The red was black at the other end. It is just a plastic colored shield.
I swapped them around so the black had black at the other end, same story for red.
Tried again with the connection and this time just a tiny spark(normal)...when connecting the cables. The Toy started up. Trouble with cross connecting is the ALTERNATOR WOULD BLOW IMMEDIATELY WITH THE FIRST BIT OF SPARKING ON A CROSS CONNECTION. That is +$200.(30 years ago)as the alternator diodes are fried(instantly) Not my fault. It was the owner of the Toyota that owned the jumper cables so they were at fault.
. but I learned from that incident "NEVER TRUST THE ENDS UNTIL YOU MAKE SURE THEY ARE CORRECT." My air cooled VW was O.K. as I had a generator. They do not like to be backwards but they lived. Pretty certain the chick had to ask her dad to fix the alternator with $$
> it happens once, you remember forever.
Syncro First gear happened in about 67(or 70) on VW.air cooled beetles. So I assume other manufacturers did so about the same time. I always drive 4 or 5 speed manual transmissions in my own cars. First is for when you are at a DEAD STOP. So it is used to get you rolling, after that, you never use it again until you are at a stop. or on a really rough bush road going uphill or downhill in the loose gravel or in the snow and let engine speed at idle be the brake.
Great info, thanks for putting this out!
Hi Wisconsin Oliver Nut! My oldest son is now farming in Wisconsin. He is really starting to get attached to his old Oliver tractor. Ha ha
They really were good tractors.
@@bryanh1944FBH yes! I grew up around Olivers in the family, so I am partial to them. I suppose this is the story for a lot of farmers/collectors. But those older tractors that don’t have “chips” are really something special when compared to things now.
I have always wondered about this, thank you so much for clarifying
A very good explanation of the positive ground system. Thank you!
Hi Okie Tom! Thank you for the comment. I am glad you enjoyed it.
This was a good video! You have given me something to really think about! Thank you!
Hi Andrew! You are so welcome!
@@bryanh1944FBH my Father was an Electrical Engineer and could never get me to understand electricity, I became a Civil Engineer.
@@andrewkast4087 Ha ha. I like that comment. Both are good! You did good.
Thank you, that's the best explanation I've ever heard.
Hi Steven and Nancy! You're very welcome!
Thanks Mr John for explaining this problem in depth. I have been trying to tell people for years that most of the problem is the small ground cable leaving the battery to the frame needs to be cleaned every 7 years or so to prevent electrical, computers or no( crank-start ). Just clean the battery cables beginning of Summer and winter. I thank you and I will share this on my Facebook page. AMEN
Better yet slather the connections with silicone grease and it will prevent corrosion in the first place, at the cost of attracting some extra dirt.
Most Excellent and thought out explanation of this ( - ) Negative ground thing.
Very interesting commentary. My 1961 Lincoln Continental had a positive ground system.
Thank you. I am glad you enjoyed.
my grandfathers 61 Mercury was 12v negative ground
@@noti51 Interesting that Ford chose different polarities between two lines of automobiles.
Great video. It's good having a RUclipsr who really is an expert in a field and isn't just making it up as they go along to get clicks. This is a bit over my head on first viewing but I'll watch until I get the gist of it. Thank you.
You remember that he said he was reading his theory. I'd say most of his conclusions are right, but not necessarily how he reached them. That's OK, that's how science works. You come up with a hypothesis, you test it, and if the hypothesis and your observations match then you have a theory. How you came up with the hypothesis doesn't matter, as long as it accurately predicts what will happen, it is a workable theory. When you detect a flaw (like the direction the metal moves in electroplating) then you update your hypothesis and test again. Science isn't an answer, it's a process. (They call it the scientific method.) And while it's a good idea to 'follow the science' it's more important to question the science. Classical physics is really good at predicting how things work, and we still use it all the time, but without quantum physics nobody would have predicted transistors, and if they hadn't predicted them they wouldn't even have tried to figure out how to make them. Transistors were discovered by mathematicians, then physicists could invent them.
@@GordieGii
Excellent comment 👌
Some of the so called experts in today's society who are repeating the ' follow the science ' frase ( but are actually advocating that the science is settled) should have a listen.
Science is never settled unless one makes the mistake to elevate oneself to God like infallibility, which is one of the ingredients of the downfall of our society.
Thank you for the info since I never knew that and I like learning new things.
I have a 1976 triumph bonneville and it has positive ground and I always wondered why now I know great video
as an automotive electrical tech and a guy who loves early British cars, + ground, I found this enlightening. did a lot of + to - conversions. never once did I revers the coil wires. clearly a mistake on my part. what you have said makes so much sense.
thanks!
just for sh**s and giggles, I'm going to woop out my HV volt meter and check my coil output and see if your correct. I expect to see -to + ground and my 20kv output - 12volts
Bryan
Your spot on!
Back 42 years ago in my first electronics class the old teacher told us the truth, that electrons flow from neg to positive. That as technicians we were to understand this. Further that our future electrical engineers would tell us the opposite. That we should be wise and not argue with them, only know that we were smarter than them. 😂
Hi RCF! Thank you.
I'm smiling because you texted "elections" instead of electrons (which probably flow from neg to neg 😅). I'm curious now what you guys think about what Tesla would have thought? (WWTD) ? He might have had all the autos driving around using the atmosphere for power eh?
@@ProjectDreamCatcher I don’t know what your talking about…. 😉😂
Anecdote: I used to work on VWs in the 50s and early 60s. All VWs were always negative ground. (Were all German cars always negative?) At the same time all English cars were positive ground. People were forever installing new batteries in their VWs in a positive ground configuration thinking all European cars were positive ground. In many cases the generator would re-polarize itself and the car world run OK except for the spark plugs failing with the side electrode eroded into a sharp point, exactly as you describe. Sidebar- Why did German cars use bolts to hold the wheels on while American cars used nuts? Thanks for the video, most enjoyable.
Hi Jim! You are exactly right!! This is exactly what happens to spark plugs when the polarity is wrong. When I remake this video, I will have to make that point clearer.
I find it easy to understand electron flow from negative to positive, excess electrons at negative to lack of electrons at the positive. Never quite grasped “hole flow” theory. Since the ignition coil is a completely isolated circuit, the collapsing magnetic field generates the positive and negative poles, thus the center electrode is positive and the tang negative.
very interesting points here, - I have seen many problems with ground connections through chassis, - tended to fix it with nice and heavy (ground) cables ...to be compatible with positive ground I would create a negative voltage battery system to go along-side my positive 12v rig ...as for 24 volt, wondering if there were / are positive ground 24 volt rigs... - it's interesting that the telephone system ran on / runs on a minus 48 volt rail - so does the power supply for PoE... - my ultimate master power system has plus and minus rails at all the voltages, - stuff like a mobile workshop, primary camping rig....
Not having music is a "positive" feature.
Ha Ha! Thanks Alan. I agree. Funny comment.
I'm 69 and grew up using and working on the old IH and Oliver 6 volt tractors and I really like your video. I dislike the sight of a lovingly restored old tractor that has been "upgraded" to 12 volts and has a bright, shiny alternator bolted on.
Hi Rick. I agree! I work on a friend's 1944 Farmall H. It can be seen in some of my other videos. It has the original generator. It's 6 Volt and works as well as the day it was made. But, generators are harder to keep going as they do have brushes. And, as we both know, good grounding on 6 Volt systems is everything! Excellent comment. Thank you.
A very good job of explaining Positive Ground vehicle electrical systems. Thank You for sharing this info.
You are welcome
Magnavox three CRT projection TVs in the late eighties to early nineties used positive ground in the transistor circuitry. The consequence of this was that for board level trouble shooting and repairs, the use of an isolation transformer was an absolute necessity!
I stumbled for a while regarding the spark plug and why some plug systems, for example waste spark systems, can alternate ground polarity. On a waste spark system, one coil powers one plug with forward polarity, in series with its partner plug with backward polarity. That's why they don't label one electrode of the plug as 'anode' or 'cathode', it depends on how the coil is wired. The spark will still fire, perhaps with different characteristics and wear features, if the secondary coil leads are swapped. Then I had an 'aha' moment, when I realized that the spark jumps at a voltage of somewhere between 6,000V and 15,000V, reaching for a path to the other side of the coil, not the battery! This is so much greater than the 12V bias, battery polarity is irrelevant, all it is really doing is giving a stable baseline. The 12V battery is a miniscule, passive bystander.
There is one thing I have observed regarding this topic.
This case I am referring too is points ignition system, If the coil is hooked up reverse ie coil + to points (B- switched) and coil - to ign (B+ constant) the spark is weak.
If connected coil + to ign (B+) and coil - is connected to points (B- Switched) The spark is strong.
I can't think of the reason it would matter unless the condenser/Capacitor is polarity sensitive.
As for spark plugs the don't care about polarity as can be seen by your example aka the coils where the secondary is isolated from the primary coil and the secondary coil has both ends of it connected it a spark plug meaning every time the coil is fired one plug sees around -15kv and the other sees around +15kv though the voltages won't be 50/50 as the cylinder with the air fuel charge requires a higher voltage while the cylinder just finishing it's exhaust stroke has ionized gas and lower pressure which conducts electricity better.
Very clear and easy to understand, many thanks Bryan. Best Wishes from the Wild West of England.
Hi! Thank you so much for watching and commenting! Best wishes to you as well!!
Makes perfect sense. I am an aeronautical engineer and I was a ElectroniC Warfare repairman in the Army.
Excellent! I bet you have fun at work. Thank you for watching.
One problem with your theory about spark polarity multi-cylinder magnetos fire half the plugs with positive sparks and the other half with negative. I've never noticed any deference in spark plug electrode wear due to polarity.
send me info.
I remember telling people I had a positive ground 6 volt electrical system in my car and that's why I couldn't give them a jump start. the reply that it didn't matter how many cylinders I had in the car was kind of funny at the time. I tried to describe them what was happening, but It ultimately just had to tell them I didn't like them and that's why I couldn't give them a jump start. They had no idea what voltage was, my 6-volt car had no hope of starting their 12 volt car. Anyway, memories of the past...
Then you should have called up your buddy with HIS 6 volt system, so you could put them in series and give the poor guy a jump. That would have been the EASIEST thing to do.
Reversing the jumper cables first (of course), 6 volts would have started it. I've heard of guys doing this. The starter doesn't care, it's just turns over, it's pretty tolerant. It may not be ideal, as too many amps at a lower voltage than what the alternator is made for could burn it out. But you'd be stepping it up going through the 12v battery anyway. Now time travel back and say, "Can-do, my friend."
@@mikemotorbike4283 I knew this specific vehicle. I had read the service manual for his Chevy truck. Connecting that starter to a 6 volt battery is how you test the solenoid. The solenoid activates but the starter won't turn. At least in that vehicle. I was pretty sure it wasn't going to start on 6 volts, but I suppose there is a chance he had some aftermarket starter that was entirely different
I remember working on a '27 Mack at my first job.
I got the job through my buddy who said I would just be changing oil and sweeping floors.
Little did I know I'd rebuild about 6 yugos from 10 of em into running cars.
Anyways a customer had a 27 Mack truck ,6v positive ground and the boss asked me how I'd hook up jumper cables.
I thought for a second and told him red to red black to black.
He asks is the running car negative ground ?
Yes.
I got a gold star.
Then he let me fix a bunch of wiring maladies it had.
I think you could could charge their battery so long as you reversed leads.
My late father flew the PBM and PBY for the U.S. NAVY. I Noticed you appreciate the A/C. I appreciate your video.
Hi Andrew! Sorry for your loss. I wish I could have talked to your father. The PBY is my favorite plane. Thank you for your comment.
Years ago I had a 12 v battery someone charged in reverse.
If a battery is totally dead and a person hooks up charger backwards the battery is reversed and negative becomes positive.
I was a marine mechanic as a kid and fixed a old guys boat no one could get running. He hooked up charger backwards by mistake.
I also had engines with coil wired reversed and true low power hard start.
Good show!
Hi! Yeah, this happens. My friend "accidently" got his boat battery slightly reverse charged. A modern "smart" charger would not charge the battery. We hooked up a load to the battery and completely drained it before the smart charger would recharge the battery. An older charger would have also worked.
I'd suggest that however positive ground became initially the custom (whether it was ideas about spark plug sparks as you've suggested -- which might also pertain to wear patterns in the distributor -- or something else) negative ground became an electronics philosophy that spread to automotive electronics once vacuum tube circuitry got off the ground, pun possible. First these vacuum tubes required far more voltage than a vehicle battery could furnish, so a vibrator circuit was provided to feed a step up transformer -- but like spark coils, that transformer can be wound or connected either way. Eventually special vacuum tubes appeared that could run directly from the vehicle battery which would have solidly cemented the negative ground polarity if it wasn't cemented already. As we know, eventually solid state supplanted vacuum tubes, and it can be constructed to operate on either polarity, though there is a performance edge with electrons rather than holes as charge carriers (hence NPN transistors vs. PNP transistors) and that favors negative ground again.
NPN=not pointing in neg- PNP=Pointing in pos+ transistor
What exactly is the performance edge since all maths work the same for electron theory or hole theory?
Lots of good information. There are some exceptions to the spark plug polarity rule. I've seen that some old gm cars had a cable operated ignition that reversed the polarity of the coil every time it was turned on. This should reverse the wear on the electrodes I would think. I'm my years with our power company I learned how on our high voltage DC line the ground rods would slowly dissolve and the material would build up on the next rod in line. They would reverse the polarity every so often I think for this reason. Another thing that is interesting is all flat twin 4 stroke engines I have worked on have a double ended coil. Power goes out one end, through a spark plug into the block and out the other plug and back to the coil. A complete series circuit. Remove one plug wire and no spark on either side. So it means that one plug always has a negative electrode and the other one is positive. I have never seen a problem because of this.
I doubt it would reverse the wear, but would probably spread it evenly between the center and the tang.
i THINK gm "waste spark" coils also work the same
.
on my 3.1 (or buick 3.8) it has 3 coils.... 2 terminals on each coil
ive also been told that you need double plat spark plugs..... due to the one plug sparking from center to "ground strap".... the other from strap to center
.
the doub plat plugs have a little "button" on the strap and center.... allowing for good spark control
The cathodic effect.
@@kainhall you need IRIDIUM not platinum, those GM engines with waste spark had pre-detonation issues because of the size of the platinum plus the inefficiency at heat removal(vs copper) iridium is so small tip that it doesnt create piston chipping scenarios and you get 100k service intervals.
I saw a switch on an old Chevy truck back in ‘62. The switch was operated by activating the starter with the foot pedal and it reversed the ignition polarity to minimize metal buildup on the points. Truck was probably a ‘36 or ‘37. Mechanic told me I probably would never see one again.
I am 67 years old, and remember the cars of old with positive ground systems. With the advent of cars with alternators and negative ground, many a time and oft' an early alternator was destroyed by the reverse polarity installation of a battery !
Trinidad & Tobago.
West Indies.
Hi ramish! Thank you for your story and watching my video.
thanks for answering the how to jump start a pos ground ,i guess i got lucky thinking like you said it doesnt matter color just direction of flow thanks
One minor problem with this theory - waste spark systems. That's when one coil is used for two cylinders. The high voltage + goes to one and the high voltage - goes to the other. The sparkplugs are in series using the bock as the connection between then. Both fire at the same time, but one is on the power stroke, the other isn't - hence the name "waste spark". These systems are picky about the plugs used since half of them are "backwards".
This is the system on my old P&H (Onan) welder. It is a shit design because if one side gets wet or flooded, slightly fouled, etc, the good side will not fire either.
The spark plugs used in those engines have a special material either platinum or iridium on both electrodes so there is no ground electrode erosion from the reversed plug.
@@MatthewBerginGarage interesting
Hi Matthew! Very interesting. Can you tell me more? I bet the plugs were very expensive! I will have to cover this point if/when I ever redo this video. I think this is a very important comment. Thumbs up to you.
Interesting spark plug, with a left hand thread... But I suspect the early part of the video was reversed as text was also reversed. Regards the ignition system, the spark plug itself gets AC, the frequency of which is determined by the inductance of the spark plug, and the value of the capacitor that is across the contact breaker. Unless there was AC (caused by "ringing" in the primary of the HT coil), there would be no induction of energy into the secondary (HT) part of the coil. Electricity does indeed flow from -ve to +ve, as evidenced by the operation of a vacuum tube. I would speculate that the advent of semiconductors into the car's electrical system was the reason that we changed from +ve earth to -ve earth. The reason that the engine does not run so well when the coil connections are reversed is that the "bottom" end of the secondary (high voltage) is connected to the "bottom" end of the primary winding, and this connection is the "CB" connection, which needs the capacitor across the contact breaker. Reverse it, and the capacitor is no longer part of the equation.
Regards changing from a dynamo to an alternator, the alternator is physically able to run at higher RPM, and as a result, has a much smaller pulley than a dynamo. This allows some generation at "tick over".
Regards,
Cossiedriver
I like that pic of the PBY-5A Catalina on the wall behind you. I used to work on and fly (in that order) one in the early 90's in northern California taking it to airshows and landing on lakes in the area.
Hi Jamel! Thank you for commenting. OMG! Do I ever envy you! The PBY is my favorite plane. I have been inside several. But, certainly have never flown in one! That picture is one of my "happy places". Thanks again!!
OK, I'm convinced. Good explanation, I enjoyed listening to this.
Hi Jonathan! Thanks for listening.
With field effect transistors, used in MOS devices like MOSFETS and digital logic IC's etc. the positive supply is labeled VDD (drain) and negative VSS (source) in line with electron flow.
Well, sorta, the source implies it connects to a supply rail. What you describe is correct for N channel devices but for P channel it is backwards and source connects to +.
That said, there is still a big advantage due to physics of using the N type devices (NPN, N-mosfet, etc) because they have better properties for a given cost than the P type devices. There are even cases where an N type device will be used at the positive side of a circuit even though it requires additional drive circuitry to operate that way, just because the actual switching component can be cheaper.
@@big0bad0brad Correct. Even inside logic chips the designers try to avoid P-channel devices.
Great video. I always thought GM led the way to negative ground in the early 40s so that corrosion would be at the ground strap instead of at the accessories.
Hi Michael, thank you for commenting. That is very interesting indeed! I've heard a similar theory on Mack trucks and body corrosion.
@@bryanh1944FBH Body corrosion vs positive or negative ground is a new one for me!
It is actually corrosion at the accessory terminals rather than body corrosion. With negative ground, the corrosion will be at the battery posts.
Quite educational, and I'm glad I watched this.
Thank you! I'm glad you watched it too.
Yep. You’re absolutely right. The power flows from negative to positive. British sports cars were still positive ground long after they switched here. I had a ‘67 Triumph Spitfire that had positive ground.
At 15:01, better to say that the distributor includes the POINTS, and the POINTS are simply a switch to GROUND. Also, if one actually wants to experiment with a reversed spark plug polarity, it's not simply a matter of reversing a few wires. The internal wiring of the coil has a common connection for both the primary and the secondary. Simply reversing the wires on the primary also messes up the secondary wiring. So, a proper experiment includes isolating the ground side of the points and connecting it to positive instead of ground. Of course, the rest of the coil wiring needs to be properly connected.
But the points are on the 12V side (primary) of the coil, not the HV (secondary) side. The cam that operates the points is on the some shaft that rotates the distributor arm but isn't electrically connected to it.
Wow. I had to look this up. The 20,000V is relative to the positive voltage coming from the battery (ignition switch), not ground. So if you want a reverse spark, you would (as you say) isolate the base of the points from ground and connect it to the positive coming from the ignition switch, but also connect the "+" terminal of the coil to ground. Of course then your spark would only be 19,988V (or maybe it would be 20,012V) but I don't think that would make any difference.
You might also have to reverse the polarity of the capacitor. If it is electrolytic, it wouldn't like to be hooked up backwards. (probably burst)
@@GordieGii Spot on!
I was personally trying to avoid tackling that explanation...
Well put.
I think it has more to do with ground loops and ground potential than serviceability. The chassis is such a good conductor that there is a negligible potential difference across it regardless of current. In a vehicle with multiple supplies and loads of different kinds (think high current loads like headlights and low current but voltage sensitive ones like electronics) it makes far more sense for the grounds to be common than the supply.
Wouldn't a positive chassis just mean we consider positive to be the common and negative to be the supply?
@@jeffreystroman2811 yes
I had a 1964 White Diesel that ran 6 to 12 to 24v series to parallel! The decompression start system was great.
Thanks. Good information for my 1955 Ford 850.
Hey nice video and good topic - I think you left out one thing that might have influenced the switchover - solid state radios. I've read that as they switched to NPN silicon transistors it was easier to use a negative ground for the radio chassis and antenna. Really it could be made either way, but it may have been more economical.
know the funny thing, if you reversed the polarity of everything and changed the NPN to a PNP, the circuit will work almost the same. I learned it the cool way after I though I could just swap the PNP to a NPN and invert the battery, but I forgot the electrolytic capacitors don't like that, you have to reverse them, thus I made a positive ground circuit.
the collest thing was mixing PNP and NPN the wrong way and they exploding
I have a diesel technology text book from college thar says it had something to do with early transistors as well.
@chuck 8094 cmos totem pole is basically almost symmetrical, its beautiful, you get it almost for free, but PNP are a bit bigger than NPN, but not by much.
In digital logic you end up needing both anyway.
@chuck 8094 "This is relevant in guitar amplifiers because of the coveted vacuum tube sound. "
I used to think that the difference was because of the cutoff of saturation of a valve vs the transistor. But that can be simulated perfectly in a circuit by the gain curves and so.
But I think to the human ear, what matters most is the kind of "white-noise" produced by the grid of the tube, transistors have none of that, ironically the problem is that they don't have much noise.
The human ear really likes the warm sound of the noise floor, its not exactly white-noise, but its noise, and it matters a lot for the feeling.
I'm an amateur guitarist.
So do I have to use left-handed thread wire nuts fpositive ground vehicles or will regular wire nuts do?
I have a 1946 M Farmall switched it to 12 volt several years ago and I left it positive ground all I changed was the regular lights and put a resister on the coil, the 6 volt generator work great with a 12 volt regular. Enjoyed your video.
Hi Delmar. Thanks for sharing. Do you remember, was your new regulator for positive ground? Or, didn't it really say? Just curious .....
@@bryanh1944FBH it was positive ground I think the one I got would work both was once the generator was polarized
I like " came from the factory that way, gonna stay that way"
Hi Steve! Yes, I want to keep the Farmall H the way it came. Thank you for your comment.
I went to engineering college and was taught that the positive ground vehicles rotted the body work out quickly through electrolysis.
Same
Regarding vacuum tube radios in cars, the first car radio to be powered by the car's electrical system instead of by separate dry batteries was the Motorola, invented by Bill Lear, the Lear jet guy, back, IIRC, in the 1930's, decades before cars went to negative ground. Those radios didnt care which way the car's electrical system was wired, because the tube filaments(aka "heaters") weren't polarity sensitive, and the high voltage polarity for the tube anodes("plates") was taken care of by the polarity of the high-voltage rectifier. "Hybrid" radios that used a power transistor in place of the vibrator, and low voltage tubes, didnt appear until the LATE '50s, 2 or 3 years AFTER the polarity change over was made. Some of the tube radios had "option" jumpers to select between 6 or 12v service. Tubeless all-transistor radios didn't start appearing in cars until the mid 60's, ten years after the switch to negative ground, and those old transistors were PNP construction, which worked with a positive ground, which required special circuits and construction techniques in the radios to be used with negative ground. NPN transistors, which worked directly with negative ground systems, didn't appear until much later. Some of the solid-state radios had options to switch between positive or negative grounds. Whatever the reason for the switch to negative ground, car radios of any sort had nothing to do with it. My qualification: This stuff was current when I used to work on it in days long past.
--- an old, OLD radio man AND car/motorcycle/boat/hot-rod mechanic.
Hi Joe! Thumbs up to you and an excellent comment. You are a wealth of knowledge. I wish you were standing in my shop and we were having a long discussion. I would learn a lot from you!! That's for sure.
Thanks for the lesson. You have a good day.
Thanks, you too Jorge.
Now this is something I need to know. I worked on a Chevy g30 based camper and van and it was such a pain in the ass to figure out how to wire up new lights.
I'm a little surprised that there is a performance difference between +ve and - ve spark ground.
I always though that it was not the flow of elctrons that ignited the mixture, but rather resulting plasma which spans from the one electrode to the other.
I have listened to this several times and I agree with the vast majority of your information.My only comment is that the ignition coils are all wired to provide a spark from center electrode to the body of the plug. You said the positive of the coil should always go to ground and technically this is true but the coils are sometimes marked Batt and distributor Some have a + on the coil not to be tied to ground. They are internally wired correctly to have the plug electrode negative point the terminal marked + or pos doesn't necessary tie to ground.
Many newer cars with coil packs actually fire 2 plugs at the same time sending voltage from one center electrode to ground tang through the engine to its mating plug tang to center electrode and back to the coil completing the circuit.
@@martyk1156 waste spark systems
@@martyk1156 Hi Marty. That's interesting. I need to learn more about that. Thank you for your comment.
Thank you the information, my grandpa owns a Farm All and an Allison Chalmers bi fuel tractor. The Allison starts on gas until it warms up, then runs on diesel. It was very unique to operate, learned when I was eleven, now I'm 44😁
Hi. Thank you for the comment. I hope the tractors are still going!
@@bryanh1944FBH he still uses them @76 years old!!!!
Thanks for the great info! I don't have a tractor myself; but I know some who do.
Hi wrecked. It's the thought that counts. Even though you don't own a tractor, I bet you want to! ha ha
I had a '61 Ford Zephyr, an English car, with positive ground. When I put a radio in it, I had to mount it on insulated fittings, to accommodate the negative-earth radio.
Zephyr's were still positive EARTH right up until 1966 / 7 when the Zephyrs / Zodiacs were on their last model, the Mk4..
I put an old Chrysler positive ground 6 volt radio into a 12 volt negative ground Ford. Had to do the same thing but it worked.
65 Ford Cortina GT, pos gr. First car . Had to wrap my head around this theory, worked well . Later I accidentally wired my73 Chevy wagon coil backwards during a tune up & experienced a crank & No start condition. Another mech noticed and advised me of my error., an easy mistake having recently sent my English Ford to the scrapper , wish I still had it. For the MPG. ⛽️
To me the primary disadvantage of the negative ground is that it causes the bodies to rust out due to the polarity on the body surface. Mechanical connections have been the source of most electrical problems and should always be thought of first. Today's vehicles have reduced the size of these such and compacted them together so much that they have created troubleshooting nightmares. Great video.
Absolutely!
Great reason, except you got it the wrong way round. Look up "sacrificial anode" (positive). With positive earth the whole body becomes the sacrificial anode and that's why it corrodes away. That's the true reason why they changed to negative earth.
Ground polarity has no effect on corrosion in vehicles since all vehicles are isolated from earth ground by rubber tires. However in underground pipes which are 'earth grounded' quite well due to being buried. Anticorrosive voltage/current is applied to underground piping systems to minimize electrochemical corrosion.
@@WJV9 You really are confused.
Ground on vehicles is absolutely nothing to do with the physical earth.
Don't get confused with earthing of mains electrical installations such as houses.
The ground of vehicles is absolutely nothing to do with earthing, and it wouldn't make any difference if there were no rubber tires.
The ground on a vehicle, is the use of the metal body work as a common connection point, an easy way to connect things together. So instead of running multiple wires back from rear lights including tail light, flashers, the brake light, the headlights, the horn, the electric window heaters, the electric window winders, they can all connect to the metal body work of the car and it eliminates a large amount of wiring.
There is no connection to "ground", or "earth". Not that any is even required.
@@WJV9 -- Well, believe it or not, tyres have enough "carbon black" to be slight conductors.
Direction of current flow depends on defining hole current or ion current. In practical application, we use Conventional Current which is based on the positive definitions of work and force - positive is considered above negative - the direction of positive charges in motion "falling downhill" from positive to negative.
Well done!
Thank you! I appreciate that.
Well, no because you could simply reverse the secondary winding in the coil to accomplish this regardless of the primary winding's polarity. Besides the spark plug will work anyway regardless of the direction of electron flow. The electricity is simply jumping the smallest gap.
I think positive ground was more a European thing than a US thing, What was real fun was putting a radio in a pre-70's Mack truck which had a positive ground system that was switched to 24v during starting (Two battery banks switched from parallel to series during starting), the installers never could figure this out so I'd have to do it. (Ex Navy ET + 38yrs as a communications technician)
You also have to consider the coil works by the collapsing of the magnetic field (Inductive kick) so the discharge would be opposite polarity of the cuttent that established the magnetic field... Why you put a diode across a relay coil reverse polarity to absorb this and keep the spike off the supply line. (Or a capacitor)
As far as the galvonic thing, this would be more to do with disimilar metals in contact than the vehicle body which is insulated from the earth by the rubber tires. I would think galvanizing the bodies starting in the 80's would be what stopped corrosion, not the polarity of the electrical system. (Which hadn't changed from those pre 80's cars that rotted out)
There are a lot of comments about wasted spark ignition systems (a topic which this video does not cover). Wikipedia has an excellent article on this topic: en.wikipedia.org/wiki/Wasted_spark_system
The article explains that spark plugs used in wasted spark systems "should" have precious metals on both the central electrode as well as the ground tang to decrease erosion and increase the plug's life. Many comments also support this. Just saying; but, I suspect these plugs are somewhat more expensive. The article also talks about the reduced Voltage needed to fire the plug on the waste spark (which also reduces erosion). Please check out that very interesting article.
Lol, I didn't know your were an IH Farmall fan when I clicked on your video. I'm actually trying to troubleshoot a 1949 Farmall A (🥰 My 1st tractor.) that turns over but won't start. I've already gone through the combustion, fuel systems and now focusing on the electrical system.
Hi! Thank you for watching and commenting! Yes, I am a Farmall Fan. I have a beautiful 1944 H (Positive ground and 6 Volt).
My favorite tool is a spark tester. It hooks up at the spark plug and you can physically see the spark jump the gap. These are inexpensive tools. Over the many years, I have fixed a lot of stuff with this simple tool and my Volt / Ohm meter.
Good luck!!
Oh, BYW: I have seen many problems with the On / Off switch not working. One of many things to test.
Thanks Bryan....Feed me more...I love electrical problems!
Hi peter! I too like electricity. But, I don't know that I will do another. Too much emotion in the topic. Im now thinking about a video about the Saturn V rocket and/or radial aircraft engines.
Wow that explains to me why it always seemed odd that the pos terminal went to distributor and not batt. I guess cause it was basically a positive ground situation. Is that correct? If so thank you for this video. If not i guess the quest is still on for me lol!
The high tension centre output of the coil goes to the distributor centre.
The very old vehicles had a Dynamo with two coils one feeding the condenser breaker point, spark plug and the other for feeding other electric thing's, like head lamps backlight, break lights and other things and they did just fine and the bougie last for decades
Hi! Very interesting. Thank you.
Bougie = spark plug or candle (!) in French.
thanx for the great speech, I can't stand music mixed in a narrative, so am very glad You only talked.
Oh I never imagined that the English at B.M.C. actually had thougth about it, when giving my first car, a brand new, 1966 BMC Mini, + to earth! But now it seems to have been a very fine idea on an otherwise, totally, hopelesly, seriously and extremely bad produced car, which never was able to start during winter anyway! And had water coming in from everywhere, also the corners of the front screen (And that needs a special talent!! It became one of my three English cars at all. The First, The Last and The Only!!! Today I drive a French car which is watertigth, airconditioned and starts when wanted!
Hi, the real reason was way earlier than prewar spark ignition systems. The early electric lighting systems were +ve earth. Reason is the awful cotton and rubber insulation of the wiring fails when it gets wet. It was to prevent wiring failing early after getting wet. Add salt to that and the failure is quick. Good pvc insulation and transistor radios/ignition systems drove the first swap over. _ve earth coils have reversed secondary winding with a few extra turns to overcome "bucking".
Hi Howard. Thank you. That is very interesting indeed.
Thank you! Finally a theory with some traction.
I had commented above, and had doubts about the ignition coil theory as well, as they can be internally constructed for any polarity desired.
This makes sense.
But why are the negative grounded vehicles “easier to work on”? You did not explain why or did I miss it?
Hi Louis! Thank you for commenting. I think negative grounded vehicles are easier to service by most mechanics because we all are trained in "conventional current" flow which is positive to negative (hence negative ground). But, that's just my theory. I have seen people somewhat nervous to work on positive ground machinery. But, with a meter, it makes no difference. All their training is still good and applies.
I kept waiting for the phrase "Conventional Current".
Look at slo-mo of lightning, it jumps up from the ground to meet with the lightning from the clouds. I had a positive earth old car and dad showed me how to swap the terminals and re-energize the generator to negative earth by running the car then carefully swapping the terminals in pulses till it swapped polarity. I may have missed out some steps so do not try this at home, but a vivid memory that blew my mind at 13yo in 1974. Another fun fact, Water and electricity behave in a similar fashion except the main water flow is in the centre of a water pipe with the edges slowed by friction whereas in electricity is mainly on the outside of the wire. That is why multiple strands are used on high volume electrical supplies.
Before anyone reverses the polarity on a gas motor with an electric starter remember you can't reverse the Bendix.
hahahaha I wonder how many never though of that , that is so funny when that happens , the look on there face's hehehe
Someone above* pointed out that starters are series wound, and as such, rotate only one direction regardless of polarity. (I have not checked this out, but I believe he is correct).
*I just saw it again, it was the author that said that...
The real reason may be caught up in the future at the time. In old tube radios there's ground and B plus at a couple of hundred volts the next-future was the first tubes whose B plus was just +12 volts which meant no vibrator and transformer to make old school power. Then the transistor which the first gen because of it's cheaper the time to make PNP transistors which favor positive ground but parts were for neg ground as transistors fully came out with neg ground have been since ever since.
That was my thoughts too.
I have not yet looked at when radios became common vs when grounds switched from positive to negative...
Also, I don't think the coils dictated grounding, since the secondary could be wound to either polarity desired. It is only an issue if it is not installed as it is designed to be hooked up AFAIK...
One would have to dig deeper to see if coils were easier to build one way (or just done that way), or if it had anything to do with the choice of grounding...
I don't think the real reasons are as clear as they may appear...
I was firmly in the "it's a corrosion thing" camp.
This was very inlighting. I never new. Tha kyou