[pic heavy] car almost caught fire, need suggestions on replacing damaged/burnt wires.

[oakdub]

So I started the car after driving it all morning and it started up great, but after idleing for about 5 seconds the engine cut off and smoke started rising from my hood. Opened the hood to check out what was going on and after a couple seconds a flame started to appear. Ran to the backyard, grabbed the hose and it was out within 20 seconds.

Here is the initial damage:



To get a better idea of the location, this is a group of cables that runs from the fuse box inside the car/on top of the battery across the bay into the alternator and engine block, the picture is right above the starter. Im assuming its the starter that caught fire.

I took everything apart to inspect the damage and get an idea of what im dealing with, pics of everything:

The main ground that comes off the battery and goes to the block:


2 connectors that go to the transmission and starter:


connector that goes into some kind of coolant sensor:


main power cable that runs from the battery fuse box to the alternator:


connector that runs with the main power line for the alternator:


main power cable that runs from battery to starter:


starter:


loom of cables that runs to the engine block:





So basically the damage isn't as bad as it could of been (entire car on fire comes to mind) but iv never done big repairs on wires so im not sure what the best way to go about this is.

I can get a new ground cable and replace it in full, same goes for the main power cable that runs from battery to starter and from fuse box to alternator. The smaller cables for all the connectors: coolant sensor, starter, transmission, alternator, I think I could cut off from a scrap car and splice in.

My biggest concern is the big loom of smaller cables that runs to the engine block, the damage doesn't look that bad but i haven't taken the loom apart yet to get a better look. If it is damaged, i don't think splicing together 50 small wires is a good idea. Would I have to replace the entire harness at this point?

TL;DR: Some cables are burnt and damaged after a small fire, should I splice in new cables or just swap the entire harness.

[vura6]

good luck personally i would of let it go and called 911 then called my insurance company

[oakdub]

don't have 2-way/comprehensive insurance

[vura6]

well then its good u save the car.. i had a fire in my trunk i put some tires in there and broke the trunk light and started a fire now the alarm thinks the trunk is open all the time and the alarm doesnt go off imeaditly after u lock it. it take like 5 mins electrical fires are the worst just because you need to find the source of the problem then just rewire everything from there. i still havent fixed my problem

[Anony00GT]

If you're not good or confident in your skills with wiring repair, replace the harness.

Also, replace the wire from the alternator to the fuse box over the battery, and clean/check all grounds. Early A4's had issues with the alternator wire being insufficient, getting hot, and melting the fuse box on top of the battery (the fuse could take more than the wire could), any chance that could be the root cause of this problem?

Either way, I'd want to know why the fire started before attempting repairs, to ensure it doesn't happen again.

[oakdub]

If you're not good or confident in your skills with wiring repair, replace the harness.

Also, replace the wire from the alternator to the fuse box over the battery, and clean/check all grounds. Early A4's had issues with the alternator wire being insufficient, getting hot, and melting the fuse box on top of the battery (the fuse could take more than the wire could), any chance that could be the root cause of this problem?

Either way, I'd want to know why the fire started before attempting repairs, to ensure it doesn't happen again.

The fuse box is perfectly fine, the fire started right at the starter and only that area is effected, not to mention the fire broke out a couple seconds after starting the car. I think its pretty safe to say that the starter was the culprit here.

[Anony00GT]

The fuse box is perfectly fine, the fire started right at the starter and only that area is effected, not to mention the fire broke out a couple seconds after starting the car. I think its pretty safe to say that the starter was the culprit here.

Then replace the starter, and fix the wires.

[oakdub]

Then replace the starter, and fix the wires.

Thats the plan, won't be able to get parts until Monday though. Im going to remove the starter tomorrow to get a better look at it and cut open the big loom that goes towards the coil pack to see how damaged it is.

[oakdub]

BTW, when im looking for a harness, any 2.0 harness should be ok. Or does it have to match my engine code (AEG) ?

[Anony00GT]

It must be AEG. AEG was the only A4 DBC engine. Neither ABA (predecessor) nor AVH (successor) will work.

AEG was used as early as 1998 in the Beetle though. So from a 99.5-2000 Jetta/Golf, or 1998-2000 Beetle. Some 2001 models were AEG also.

[oakdub]

OK thanks for the info, there are no markings on the harness that indicate what engine code its from right?

[Anony00GT]

Don't think so.

Match up the throttle body connectors.

[oakdub]

Little update, picked up almost everything i need from the scrap yard today.



Only thing im missing is the right connector for my transmission. Every car at the scrap had a circular style connector and mine is rectangular. The wires are identical and all but i can't reuse mine since its burnt to a crisp.

And on a more important note, does anyone know the proper way to splice together/repair wire harnesses? According to VW they only approve their own special crimp connectors and say you should never solder harnesses.

[Anony00GT]

Yes. VW recommends W-crimps because they're pretty much idiot-proof. Butt connectors make a horrible connection, as does a subpar soldering job.

If you're good at soldering, you can solder the wires, but it must be a very neat soldering job. If you're not so good at soldering (many people aren't), then use the recommended W-crimps. The crimps and tool can be found online.

[oakdub]

Yeah Im leaning towards the crimp route> I tried to refresh my knowledge on soldering last night and I couldn't get the solder to flow onto the wire like every video I saw. Im guessing my 25watt iron isn't powerful enough to heat the wire properly.

Not to mention some of the wires in the bay are in horrible locations where soldering would be a nightmare.

[Cee-dub]

Could have been worse! My poor neighbour's Jetta caught fire in our parking lot the other weekend - looked like shoddy wiring by the PO. Unfortunately for him the hood release seemed to melt early so the fire dept. had to use their own (read: 4 ft. pry bar).





Check the melted headlights!

[oakdub]

^ that really sucks, could of easily been my car if I had happened on the road somewhere.


Anyway, forgot to update this. Got everything back together and also cleaned up a lot of stuff in the bay while I was there. Finished a couple weeks back and everythings been fine since then. I even managed to get rid of my CEL

Overall it was a good learning experience and didn't really cost me much.

Before:



After: