Caught an electrical fire while it was happening!

[bfloyd]

Took my car to the AACA car show yesterday up in Red Boiling Springs, Tennessee. Typical show... cars everywhere, people everywhere, and more "flux capacitor" jokes than should really be allowed. Anyway, I was sitting in my lawn chair at the rear of the car talking with an elderly gentleman about my car when he said, "Is there supposed to be smoke coming out of there?" I looked up and smoke was starting to pour out of the right side of the engine bay, right above the alternator. I leaned over into the engine and sniffed to see if I could tell if it was fuel or electrical. It was definitely electrical. I ran around to the passenger side of the cabin, flipped up the passengers seat and flipped off the battery cut-off switch which is installed in the battery compartment cover. The smoke stopped, but the smell and smoldering continued for a little. By now I had a decent sized crowd around my car. I really think the old Chevy and Mopar guys wanted to see a Delorean burn.

I crawled under the rear of the car and found the source of the fire. On my car, there are 6 brown wires all coming together and terminating to one bolt on the rear of the alternator.
One of the wires was bent over in such a way that it's insulation was rubbing the rear case of the alternator. I guess it eventually rubbed-thru and was shorting out on the rear of the alternator. It got hot enough where it started to melt the wires above it too. I removed the key from my battery switch and then used a flat blade screwdriver to bend the ring terminal out away from the alternator case and then wrapped the crap out of it with electrical tape. If I hadn't been right there when it happened, it probably would have caught the whole car on fire.

https://i.imgur.com/qmieTIGh.jpg

Drove it an hour back home after the show and everything seems to be fine. I'll clean up the wiring mess and heat-shrink everything one night this week.

[Gregadeth]

Man, close call. I'm glad you were able to catch it quick before anything bad happened. How long had the car been parked for when this started happening? What are the extra wires for?

[OverlandMan]

Very glad you caught this before it got worse. Now I'm going to check mine just to be safe! I also have a battery cutoff switch on my car and highly recommend having one for a handful of reasons including this one.

[bfloyd]

What are the extra wires for?

I'm not really sure. The alternator is a cross-reference from an 84' Cadillac Eldorado. When I bought the car, it had the same alternator, and when it died, I simply replaced it with the same. I haven't added any wiring to it, it's how I got it from the previous owner.

[FABombjoy]

I'm not really sure. The alternator is a cross-reference from an 84' Cadillac Eldorado. When I bought the car, it had the same alternator, and when it died, I simply replaced it with the same. I haven't added any wiring to it, it's how I got it from the previous owner.
Looks like a GM "SI" style alternator. One goes to the battery light, and one is a 12v "sense" wire.

[DavidProehl]

Glad this turned out well. Good thing this happened when you were by the car and not after driving it home, parking it in the garage, and walking away!

[Bitsyncmaster]

For everyone, inspect and tie all those wires away from metal on that side of your engine. Nothing there is fused and a wire cutting the insulation to engine ground will most likely start a fire.

[FABombjoy]

For everyone, inspect and tie all those wires away from metal on that side of your engine. Nothing there is fused and a wire cutting the insulation to engine ground will most likely start a fire.
This 100x

The factory routing for some of the high amp wires had them against the frame and frame seam. I went through and added looming at key positions for added abrasion resistance.

When you assess these wires, a person also needs to be conscious of the fact that the engine moves around a fair amount during normal operation.

I would also suggest that the B+ wires on the alternator should be tightened after the alternator is in position. Don't tighten the positive post and then tension the alternator against the belt or those cables might want to rotate around to their naturally neutral position.

[Josh]

there are a few un-fused circuits with the factory harness, kind of scary.

[bfloyd]

Good thing this happened when you were by the car and not after driving it home, parking it in the garage, and walking away!

I had just gotten back from the food tent after being gone almost 30 minutes while standing in line, and I was getting ready to go walk over to the vendor tents when this elderly gentleman walked up and started talking. I guess I got extremely lucky on Saturday.

[David T]

The whole electrical system in the Delorean leaves much room for improvement. Typically there is a fusible link to prevent this kind of thing. The whole ground side is "missing" and should have it's own dedicated harness. Because this was done by Lucas, they like to switch the ground side of things as opposed to everyone else who switches the positive or HOT side. By switching on the ground side there are many more ways you can have problems. By not having a good grounding system, backfeeds can cause all kinds of weird, hard to troubleshoot, problems. Many circuits are wired with wires too light for the current they carry. I can go on but you get the idea. One way to prevent this kind of thing is a yearly inspection. Good thing you had a master switch so you could quickly shut things off!

[Bitsyncmaster]

The whole electrical system in the Delorean leaves much room for improvement. Typically there is a fusible link to prevent this kind of thing. The whole ground side is "missing" and should have it's own dedicated harness. Because this was done by Lucas, they like to switch the ground side of things as opposed to everyone else who switches the positive or HOT side. By switching on the ground side there are many more ways you can have problems. By not having a good grounding system, backfeeds can cause all kinds of weird, hard to troubleshoot, problems. Many circuits are wired with wires too light for the current they carry. I can go on but you get the idea. One way to prevent this kind of thing is a yearly inspection. Good thing you had a master switch so you could quickly shut things off!

There are few ground switched circuits. Like every other car, the door lights use ground switching. The hot start relay uses ground switching and the idle motor also uses it. There is nothing wrong with switching the ground as long as the positive feeds are fused.

[Josh]

Ground switching is very common in modern cars Dave.

Everything related to the gm engine wiring I am running is ground switched for example.

[Bitsyncmaster]

Ground switching is very common in modern cars Dave.

Everything related to the gm engine wiring I am running is ground switched for example.

Ground switching is great for electronic switches (transistor or MOSFETs). If I was the designer, I would use is on everything.