How to Test a 7 Pin Trailer Connector with a Multimeter and Troubleshooting my Trailer Wiring
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- Опубликовано: 19 май 2022
- My trailer lights and brake controller recently stopped working and I had to troubleshoot the problem. In this video, I show how to test the 7 pin trailer connector with a typical Multimeter. Turns out it was a problem with the trailer wiring and connector.
My hands are in the way so I displayed a diagram in the upper right of the video that shows the the location of each pin to test the trailer connector. To test, refer to the diagram and the following instructions:
1) Turn on vehicle ignition.
2) Go to trailer connector with your multimeter and set it to measure DC volts. You may want to test it on a random battery to make sure it's in the correct mode and working properly.
3) To test the trailer connector, put the black probe on "-12VDC Ground", according to the diagram
4) Put the red probe on the circuit that you are testing. For example, to test the trailer running lights, put the red probe on "Running Lights", according to the diagram. For things like brakes lights, you may need someone in the car to apply the brakes while you measure voltage.
5) You should get voltage between 11-14 DC volts (depends on condition of battery and whether is is being charged/drained) 
Авто/Мото
My hands are in the way so I displayed a diagram in the upper right of the video that shows the the location of each pin to test the trailer connector. To test, refer to the diagram and the following instructions:
1) Turn on vehicle ignition.
2) Go to trailer connector with your multimeter and set it to measure DC volts. You may want to test it on a random battery to make sure it's in the correct mode and working properly.
3) To test the trailer connector, put the black probe on "-12VDC Ground", according to the diagram
4) Put the red probe on the circuit that you are testing. For example, to test the trailer running lights, put the red probe on "Running Lights", according to the diagram. For things like brakes lights, you may need someone in the car to apply the brakes while you measure voltage.
5) You should get voltage between 11-14 DC volts (depends on condition of battery and whether is is being charged/drained)
This is the best trouble shoot from brake controller to the trailer light connection I've seen. Thanks much.
Thanks, Buy yourself some Test Leads with Alligator clamps on the ends and save yourself a lot of trouble. I do appreciate the video showing the "jumping all over the place" LCD meter display for turn signal operation.
Thanks this was extremely useful and I was able to ensure my 7 pin connector is good! I knew there had to be a way with a simple multimeter, great video 🤘
Glad it helped you Jeremy!
Thanks for posting! Just what I needed.
Great video, I appreciate the walkthrough. 👌
Thanks for the video,,I need to check the brake voltage output.
You made it simple.
This is very helpful . . . thanks for your time and effort !
You’re not kidding - you’re the only video I’ve found on this
Very informative video. I was not expecting to learn all of that. Make more videos man.
Thanks!
Thank you for the video. This really helped me alot. The only concern / deviation is the fact that I get no volts registering whatsoever with the black probe on neg./neutral, and the red probe on hot. All else is just as you show. Anyway, lights on trailer work great, no issue. 2004 Suburban, BTW.
I just installed a brake controller on a neighbors truck. Since he didn’t purchase the vehicle with a tow package, that hot wire was not wired to the rear of the vehicle. And the fuse box in the engine bay also had the brake controller wiring not connected and tucked / stowed away.
Thank you! Excellent video.
Thanks for the share. My brand new truck's connector isn't connected On a truck, lol. This saved me some trying to validate this with other means.
This helped a ton with an issue I’m having! Thanks!
Glad it helped!
Thanks for sharing God speed 🙏
Excellent video! Thank you so much. I needed to know how to test from the socket because the Toyota engineers never tried used the tool they provide (which is located in the engine fuse box) to take out a fuse. Impossible! Mine is a 4runner.
Awesome job
Good video, saved me time and money since I had a multi meter, of course still not sure why my lights aren’t working but my brakes are 😑
Check your fuses
Great Video, thanks! I was hoping you would do the MM Test on the Reverse Lights, I have a boat trailer that should have a "reverse override" so the Brakes don't get applied when backing up, up hill.
Also, it would have been good to see the individual connections from the new Plug to the Trailer, as I don't think it was a simple color to color match as the initial diagram showed.
Great vid! I was going to make one myself!!
super helpful!
Well he'll. I thought the center pin would be negative. Now I'll go test again. Thank you.
Logical mistake. :)
I still got my Analog meter!! 😂
lol, me too!
I have to do this, and also figure out why I turn my lights on the 2005 Yukon, and it's in Park, my RV brakes turn on also.
Hi, thank you for sharing, what you did is the black goes to negative and the red goes the rest 6 slots?
Yes. Black probe stays on negative. If you look at the diagram in my video, putting the red probe on the various pins should display 12-14 volts when the brakes are on, running lights are on, blinkers are on, etc.
Constant current is needed to charge the battery for the trailer brake-away system . 5/19/23
Can't see what pins you are touching because your hand(s) block the 7-way in nearly every instance! The diagram to the right of the picture helps a bit, but we still can't see where your probes are located. 😞
You're right Leigh, sorry about that! I put the diagram up to help make it more clear. Just know that whatever function I'm checking, the black probe is always on "-12VDC/Ground" and the red probe is on the function's corresponding pin according to the diagram.
Bruh he said he put it on the negative and positive. He also Eben put up the diagram. Everything he put the price he says what he put it on. So you just gotta see the diagram to probe. This is easy. Just listen and follow.
He explained exactly where he was putting them, and a quick Google search tells you exactly what pins he is touching.
Thank god someone said it!!
Helpful video, but it’s not clear to me how you isolated the issue to the trailer plug. What was your issue and how was it resolved by changing the plug?
You're right WCO. I didn't have footage that showed the trailer's 7 pin connector wiring had separated from the pins and that was the reason I replaced the trailer's cable. After testing the Telluride's 7 pin connector and finding that it was good, I knew the problem was with the trailer wiring. In my case, the trailer's connector and connector wiring was old and had been serviced in the past. I took apart the connector and saw wiring that had disconnected from the connector's pins.
Thankfully
You can make a test lamp with a bulb and a couple wires. :)
Good video, but hands are in the way to actually see check points.
I got nothing. I am trying to find out how to see if a fuse or relay blew out inside the truck fuse box?
Thanks
Can you tell me what the function of the auxiliary pin is on an RV?
The Aux pin is always hot delivering a constant 12V to the RV when plugged in. This will supplement the RV's existing battery(s) or power the RV's 12V devices if the RV's battery(s) are disconnected.
Sure we analogue meters. They show some readings very well, perhaps better than digital.
Good video, but can't see the wires you touching.
So i did this and its all working but when i connect the trailer, the trailer lights will either only work with the truck running lights off and when on the stay on as if im holding the break. And now the right turning signal will only work but not the left. And just bought this trailer like a month ago
If the trailer is new, the most likely culprit is the tow vehicle wiring or connector. Just test the pinouts and see what you get.
What setting do I put my multi meter on ?
You're looking to measure 12 VDC so set your meter to "Volts DC"
I have used a digital multimeter, and a test light, and I can not get nothing, all the pins are dead. I need to hook a trailer to my truck. Please help
I thought your video was ok, 100% could have been improved by finding something to hold the plug flap open. Also would have been nice to see the voltage reaction of the brake controller which is my current issue. Thanks for trying though! haha
Good video. Question for all. My trailer has the same plug and turn signals, brakes, hazards, stop lights all work great. UNTIL I turn on my running lights, then I loose all of the trailer lights. Tried on another vehicle and problem same, so believe it's the trailer. Any ideas?
You pretty much ruled out the tow vehicle, but if you want to be certain, just hook 12v directly to the trailer pins to see if the running lights work. If not, you know the problem is with the 12+ wire to the lights, or a bad ground at the lights. You could check continuity at both ends to see if there's a break or pinched wire on the 12+ side or bad ground connection at the 12-.
bad switch, or a short
When I try this on my 2021 Silverado 2500 I get no readings on my 7 pin connection on the bumper or the truck bed. When I run the same test on my wife’s Tahoe, it all reads the way the video goes. Does anyone know why my Silverado wouldn’t have any readings on the connections?
apparently new vehicles with the newer electronics built in won't send power to the pin unless it detects a load. so you won't get a reading on the meter.
There is no power going to the right blinker/brake light (right side) bad wire? Or what do you think?
If it's just the right side it's probably a bad wire.
@@PIFDIY i figured it out there are 2 extra 10 amp fuses for towing lights/turn signals under the drivers side steering wheel, behind the OBD2 reader.(At least for my vehicle) One of them was bad. Replaced it and it worked! I saw another RUclips video i will post link to it Incase anyone else sees this comment. Thank you for the video btw 🙌🏽
@@PIFDIY ruclips.net/video/Wy3tEUyuhYA/видео.html
@@eirod Ok Ivan, having two separate fuses (one for each side) explains how one side could be bad while the other good. Unusual set up I believe, glad you figured it out!
why not wire right into the junction box?
lovin the adds youtube
Have power with pos and neg. But get nothing on any ither pin. What can cause that ?
ok
i suppose "NOTHING" Specifically means NO VOLTAGE
Ok do this (now keep in mind i'm in Sydney and you're probably in america) it's still ok though the concept is the same.
you either have a round connector or flat connector (we use the flat one)
the connectors are either 5 pin or 7 Pin
we use the 5 pin version because we don't have brakes on our box trailers
In any case, this is just Ohm's law, it's not complex , IT'S JUST A CIRCUIT AT THE END OF THE DAY and try to see it as such
1. LET'S START WITH BRAKE LIGHTS (Brakes on the car, not on the trailer)
- Is the key in the ignition ?
- Do you have the car turned onto ACCESSORIES or either ENGINE ON ? if you're in Position 1 (The electricals are not on, it won't work)
Basically we are confirming that the brake lights on the car work
If you think it's all connected
- Get someone to stand at the back of the car, Press the Brake and confirm that the brake lights come on
(Do this without the trailer connected)
if they don't come on (that's why the trailer lights are not coming on)
Check fuse for the brake lights, Check wiring
- Now connect your trailer
Do the same again,
IF THE CAR BRAKE LIGHTS DO NOT COME ON - You have a SHORT CIRCUIT from the connector to the back of the trailer somewhere in the wiring
IF THE CAR BRAKE LIGHTS COME ON BUT THE TRAILER LIGHTS DO NOT - You have an OPEN CIRCUIT (Broken Wire somewhere)
NOW ON THAT KNOWLEDGE
with the trailer unplugged,
CHECK BOTH INDICTORS AS WORKING
CHECK IF THE NUMBER PLATE LIGHT LIGHTS UP (when either the car is ON or Key in the ACCESSORIES POSITION
if this is all good, the problem is with your trailer (first and foremost)
NOW.. IF THIS...
"Have power with pos and neg. But get nothing on any ither pin. What can cause that ?"
MEANS, You have No Power on any other pin AT THE TOE BAR CONNECTOR ON THE CAR........ it means the mechanic hasn't wired it correctly.
if he has you should get all your voltages at the car connector
if you're talking about ... at the other end
then the trailer is the problem
THE MOST COMMON CAUSE OF NOT GETTING VOLTAGE IS
OPEN CIRCUIT or
SHORT CIRCUIT
Open Means... A Wire is broken somewhere.
Short Means... 2 Wires that a not supposed to be touching are touching
ALSO ARE YOU TESTING IT CORRECTLY ?
ARE YOU SURE
Your RED Probe goes onto a POSITIVE Pin
Your BLACK Probe goes onto a NEGATIVE Pin or Ground
If you test from a Positive to a Positive IT WILL READ 0V even though there is 12V Present
Example.. If you put your probe on the RED Wire (the Brake Light) and then on the BLACK Wire (which is actually the Positive as well) YOU WILL GET A READING OF 0V or you will blow something
The White Wire is Negative
ALL THE WHITES SHOULD BE CONNECTED TOGETHER
if they are not, you have an open circuit on multiple circuits
which is .. what you are describing
so let's say you have
INDICATOR
BRAKE LIGHT
NUMBER PLATE LIGHT
(this is 3 circuits, but you have to count the white wire from the car)
so, this means there should be 4 Whites connected together
You might find that 2 whites are connected and the other 2 are not
THAT WOULD EXPLAIN WHAT YOU'RE GETTING
Because if the common ground is not connected, you have an Open Circuit
Does that help
Did you put some sides on the trailer yet
"Blinker" AKA turn signal.
the brake controller always live +?
I don't believe so. If you apply the brakes, the brake controller will put out a voltage on the pin. A proportional brake controller will vary the voltage on the pin depending on pedal pressure but voltage would be 0 when brake is not used.
@@PIFDIY thank you
Use enough solder for those connections?
Great video. What the heck is that huge watch you have?
Why would anybody think that most people have a multimeter more than they test light.
Your explanation at the start about the pins is very vague.. You didn't explain when to turn on the car and what setting to put the multimeter on..
Your Hand blocks everything!!!!
You never showed us what you said you was the trailer pin voltage
ruclips.net/video/8FxnEwmmAnA/видео.html This will always be the same voltage as the car battery.
I have aSimpson 260🤣🛫 and I will be using tomorrow for that very reason it is analog! My brakes are not activating on a 2019 Casita. We have the Curt Echo remote brake Controller. It plugs in the 7 pin then the trailer plugs into the curt. My brakes stopped working a couple of weeks ago. The electro magnetic hums when activating the brakes with the app or by the car brakes. 🤯
Your hands are in the way. I can't see what you doing which is what I want to see. Where do the probs go?
Elizabeth, refer to the diagram in the upper right in my video. Put the black probe on the "-12VDC Ground" and the red probe on any of the circuits that you are testing. For example, to test the trailer running lights, put the black probe on "-12VDC Ground" and the red probe on "Running Lights" according to the diagram. When testing, make sure that your multimeter is set to measure DC volts and the ignition is on. For things like brakes lights, you may need someone in the car to apply the brakes.
@@PIFDIY Thank you so much for this information. I rely on these videos to make sure I'm doing it right.
"Nobody shows you how to do it with a multi-meter... and neither do I" 🙄
*you
No jp
Hey! I have an analog meter!!!
Do it over without showing your hands and forearms...
Thanks for blocking the view wasn't helpful
spray bomb your trailer 3 can a paint will bring it back to new look easy fix
Some engineer out there needs to forget about trying to figure out how to add another computer, make your truck drive itself, over complicate the exhaust to appease the EPA, and make a simple FUCKING wiring harness that lasts more than 2 years! Also, this guy is one of the few people on RUclips that correctly knows how to troubleshoot with a multimeter. Teach your kids this cause chatAI is not going to wipe their ass and fix the trailer lights for them. This Country needs more mechanics and less computer. Rant over, thank you
To test a 7-pin trailer connection with a multimeter, follow these steps:
1. **Set Up the Multimeter**: Turn on your multimeter and set it to measure voltage (DC voltage).
2. **Identify the Pins**: Refer to a 7-pin trailer connector diagram to identify the pins:
- Pin 1: Ground (usually white)
- Pin 2: Tail/Marker lights (usually brown)
- Pin 3: Left turn/brake light (usually yellow)
- Pin 4: Right turn/brake light (usually green)
- Pin 5: Backup lights (usually blue)
- Pin 6: Brake controller output (usually red or black)
- Pin 7: 12V power supply (usually black or red)
3. **Connect the Multimeter**:
- **Ground**: Place the black (negative) probe on the ground pin (Pin 1).
- **Power Supply**: Place the red (positive) probe on the 12V power pin (Pin 7). You should read 12V or higher if the vehicle’s ignition is on.
4. **Test Each Pin**:
- **Tail/Marker Lights**: Turn on the vehicle’s lights and place the red probe on the tail/marker light pin (Pin 2). You should read voltage.
- **Left Turn/Brake Light**: Activate the left turn signal and place the red probe on the left turn/brake light pin (Pin 3). You should see the voltage pulsing with the turn signal. Press the brake pedal and check for a constant voltage.
- **Right Turn/Brake Light**: Activate the right turn signal and place the red probe on the right turn/brake light pin (Pin 4). You should see the voltage pulsing with the turn signal. Press the brake pedal and check for a constant voltage.
- **Backup Lights**: Place the vehicle in reverse and place the red probe on the backup light pin (Pin 5). You should read voltage.
- **Brake Controller Output**: If you have a brake controller, place the red probe on the brake controller output pin (Pin 6) and activate the controller to check for voltage.
5. **Check for Ground**: Switch the multimeter to continuity mode. Place one probe on the ground pin (Pin 1) and the other on a known ground point on the vehicle chassis. You should hear a beep or see a zero reading, indicating continuity.
### Safety Tips:
- Make sure the vehicle's ignition is off before connecting or disconnecting the multimeter to avoid short circuits.
- Be cautious when working with electrical connections to prevent any accidental shorts or damage.
This method ensures that each pin is correctly providing the expected voltage, confirming the functionality of your 7-pin trailer connection.
I would not have soldered those wires, I would have used but splice connectors with heat shrink tubing. In airplanes wires are not soldered due vibrations can break the soldered joint. If two wires need to be connected they connected vis terminal block or but spliced.😁🛫
I have to disagree. The aviation industry may have developed that solution for airplanes but that doesn't make it a best practice for all environments. The vibrations and shock to the wiring of a road going trailer are totally different. A passenger or cargo jet in constant service would subject its electronics and wiring to long term sustained vibrations at a frequency/amplitude that are determined by its propulsion and buffeting. Not nearly the same environment as a trailer that's pulled over a road surface.
This is one of those rabbit hole discussions and imo both solutions would work fine in my application as long as they're done PROPERLY.
I'm an Engineer
I WOULD HAVE SOLDERED THEM (and i did on my trailer)
So long as you solder correctly
- Clean solder tip
- Use Flux
- Heatshrink the connections
- Waterproof the connections
- Secure them in something like conduit or a junction box
- Then waterproof the conduit and / or Junction box
But comparing a trailer to an airplane is ridiculous, You can't compare a trailer to Avionics LOL
You can use a termination block (FYI, it's TERMINATION BLOCK, Not Terminal Block), that's fine, but it depends on how much space you have as well.
but as for solder joints... IT'LL BE FINE MATE, I've done this for years with my mates, and on my own trailer, going on 15 years now.. Still not a single problem.
My mates who did it themselves with knife connectors, THEY FELL OFF OR BROKE OFF
My joints are still going good
again... IF YOU DO IT PROPERLY .... it works