STRANGE electrical fault. YOUR help is needed! MK1 ford fiesta
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- Опубликовано: 20 янв 2024
- First job in getting Alice my zetec converted mk1 ford fiesta on the way to Silverstone is the mysterious electrical problem i've been having.
I really need your help on working ut whats wrong.
links:
www.mikethemechanic.se
events.fastcar.co.uk/ford-fair/ 
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Back in the day, for cars had to have DRL's, like in Sweden, some manufacturers (I know Toyota for sure) did this by running dip beams in series, ie 6 volts each, with engine running, and they did this through an extra relay pack. On switching the lights on they went back to running dip beam in parallel as per normal. That may be what your little box was for.
Ok I'll look in to that
The original double relay and double-double fuse is probably a safety thing.
I can tell you from first hand experience that putting both l/r headlights on the same fuse and/or relay is a very, very, very bad idea.
I had a fuse go bad (Biltema... It looked fine, measured fine, worked fine for about 12 hours after installing the kit, but there was a hairline crack in it) after hours of driving with no issues whatsoever, and everything just went pitch black when doing 110 kph on a dark country road in the middle of nowhere! We were lucky to be on a straight bit and no traffic or things could've ended very badly for us, and for my Chevelle. This was the last drive of the season for me back in September but I'll be rewiring the headlights with separate fuses and relays for left and right so that there is a backup if one side goes bad.
It’s been a long long time since I serviced an alternator this small, but here’s a few things to consider. Not a diagnosis per se, but y’know, it might help…
1/ the diode pack on your alternator converts the 3 phase AC coming out of the windings to DC, but has no impact on the voltage. Normally when running the diode bridge is balanced, and as a result the connection in the middle that connects to the dash warning light is at 0 volts, I.e. no light. Unless of course the engine isn’t running, so the generator isn’t generating, and a leak through voltage reminds you the light is still there. If a diode shorts out the voltage at the middle of the unbalanced bridge goes up, and so the lamp lights up. Your lamp goes out when you run the engine without an electrical load so the diode pack is probably fine.
2/ the ac generator will merrily pump out a shed load of volts if left to it’s own devices, in fact it can generate way to many volts to be safe. The voltage is regulated by, of all things, a regulator. This device controls the excitation current to the rotor and therefore the magnetic field in the rotor, and in doing that controls the voltage.
The fact you see only 12 volts when running is not a good sign, with hardly any load it means the regulator probably isn’t regulating. A fully charged lead acid cell should give 2.2 volts. You have 6 cells in a battery so 2.2 x 6 = 13.2 v. ‘12 volts’ is therefore, just a bit misleading, so a 12 volt system actually running at 12 volts actually isn’t that healthy.
You should be seeing around 13.6 volts when the alternator is running and the battery is charging. Put a multimeter across the battery terminals and check. If it’s low, the regulator may be faulty, and the 100+Watts (8+ Amps) you’re putting on the charging and battery circuit with a high beam is dragging the voltage down to a level where the alternator is just not functioning.
The fact you’ve thrown a modern engine in might be a factor too. Older engines such as the 1100 cc lump of pig iron you dragged out have super simple charging circuits as described above. In more recent times OEMs have played games with regulating alternator outputs from the ECU, enabling them do stuff like increase voltage when you come off throttle, so increasing the engine braking effect from the alternator and harvesting a bit of free juice, then when you open the throttle, the ecu drops the voltage output of the alternator, taking load off the engine and sneaking an extra 0.00001mpg and a couple fewer carbons out of the exhaust. Some manufacturers even play games with altering charging voltage over time to account for aging of the battery, leading to uninformed DIYers changing batteries and wondering they only last a year. The reason of course is that unless you tell the ecu that you’ve fitted a new battery, it will overcharge it and eventually kill it. Now Ii’s just a guess but a modern alternator deprived of this ecu signal may well default to the very low output voltage you are seeing to prevent damage. Or it might just be knackered…
As for the double relay on the headlights? Having run a standard mk1 fiesta that didn’t have this relay with 100w headlights, I can tell you some degree of certainty that the standard wiring doesn’t like it. It lets all the smoke out of the loom in pretty short order. Given that Sweden spends a lot of time in darkness, I imagine more powerful headlights than the glow worms backsides fitted in the uk are a fairly standard fitment. This relay might just have been fords way of preventing wiring fires and fitting more powerful headlights in that market.
Wow that's the longest comment I ever had 😂. Thank you so much for taking the time to write that much. I'll get a multimeter on it and see what it's actually producing I think the gauge isn't very accurate as it's just a cheap one. I think the big silver relay was fitted to the European market as it is not shown in any haynes diagram, well they don't show much anyway but definitely not this relay. Everything seams to be working fine now and it's charging as it should do I think. Thanks once again for your comment I really appreciate it.
@@mike_themechanic Quite alright Mike, you’ve thrown enough info out into the world to warrant getting some back. It may be wrong, but I’d definitely check that voltage. Neither that relay, nor the one under the dashboard seem to appear in the autodata manual for this car either. I say ‘appear’ because of the cruel joke being played by publishers that know only too well that anyone old enough to understand these wiring diagrams and the arcane systems detailed within is by default too old to have the eyesight sharp enough to actually read the bloody things.🤬
@Zofsm I found myself trying to enlarge the haynes manual with my fingers to zoom in on the picture the other day 🤣🤣🤣. I can't find anything on the computers that we use at work either so it's all a matter of tracing every single cabel to see where they go
Mike, try running the engine with the alternator check light wire disconected. Lets see if you have some ground for the check light and high beam mixed up… I hag a similar situation with aftermarket electric fan on one of my cars. It only ran when alternator was not charging…
I'll test that
I think all the advice below is good. I've got to add that 12 volts with the engine running is not enough. You should be getting 13.8 volts. Perhaps you are and your meter calibration is off a little and this is also not the problem. Something is going on to drag your voltage way down when you turn on the lights. I like these Mk 1 Fiestas, but we got only a few in the US and when people were done with them they threw them away.
I'll check it with a multimeter as soon as I can
Looks like some sort of back feed problem. In older American vehicles, alternator voltage regulators and flasher relays use the case as ground. Seeing that your relay isn't bolted to the chassis, and everything is painted nicely... that could be insulating the case from ground. Just for a test, run a jumper wire to the case and see if you have better luck. Cheers, from Canada.
I have tried to add an extra earth to the alternator but it made no difference unfortunately
@mike_themechanic the little relay that you know goes between the alternator circuit and the headlight circuit is hanging in the air, do things change if it is clipped to the dash frame?
@1quickchevy2 no makes no difference
@mike_themechanic ahh sorry man, worth a shot. The old signal light flashers used the clips to supply ground to the bimetalic strip inside, thought it might be something simular. Hopefully you have a good wiring diagram and can figure it out.
I'm sure I'll get it sorted eventually. Biggest problem is that the wiring diagram dosent show any relays 🤦♂️🤷♂️
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Im assuming your earth connections are all good and clean etc? Basic i know but sometimes the simple things are overlooked
New earth's to the same point from the battery to the engine.
Ok 👍 12v running seems a little low. Weak alternator maybe? Electrical faults drive me mad
According to the box it's a 60amp alternator and that should be plenty.
Ahhh ok. I've got a 75amp for mine.
It's a lucas a127 alternator. Charges about 13.9v when running. Very strange fault you've got there
@@minihudders94 there is absolutely no room for anything bigger in that space unfortunately.