engine and drivetrain Who likes burnt wires?... (not me)

[Meintii]

Well the other day I was trying to start the tii, and it was turning over slowly as if the battery was dead, so I hooked up the charger and let it charge up. The next morning I went to start it, and then I saw smoke coming from under the hood. I turned to key off and the engine was still turning over with the key out of the ignition, as the smoke kept coming.

Looked under the hood and this wire was smoking as it burnt up.

Its the brown wire that connects the voltage regulator to the three prong plug that goes to the alternator.

The other wires that were with this wires are blue, black.

My question is- why did this wire melt, and what needs to be replaced other than the wire?

Here are some pics

[dubois]

My question is- why did this wire melt, and what needs to be replaced other than the wire?

It is a 30 year old car, same thing happened to me, I have a quick battery disconnect and a fire extinguisher since.

[Meintii]

So do you think the wire just was exposed somewhere and lit up? Why did it melt?

[dubois]

So do you think the wire just was exposed somewhere and lit up? Why did it melt?

My uneducated guess is that the insulation around the hot wires starts breaking down, the plastic due to age starts shorting out with other wires or grounds around it - nothing last forever - that's why some people do a complete re-wire. I replaced all the damaged wires, which was not pretty. Ideally a new wire harness is the way to go.

[Bill_Riblett]

Given your symptoms (slowly turning at startup), I think your battery cable ground to the engine is bad and that the brown ground wire to the regulator wound up acting as that ground and was overloaded to the point that it melted everything around it.

The original battery ground strap has two ends, one of which goes to the body and the other to the engine. Make sure that all these connections are good before you do anything else. Then you are going to have to replace all the melted wires.

[#73]

speedwell,

I second the motion on having secure double grounds. Cleaning ground mount point, mount surface, adding a bit of dielectric grease, and tightening with clean/new hardware are the basic way to go about this. When I had a poor connection at these points, the rest of the wires and some parts of the car body would try to 'find a way to complete the circuit'. Shrink tubing exposed wire ends is a fair preventative also.

Cheers,

[stone02]

Hi,

Bill_Riblett in Arlington, VA , is exactly right.

this is a very common occcurence on my customers

cars. the grond from the alternator to the motor

gets old and the ground from the battery to both

the starter and the body corrode. once this happens

the starter looks for a draw from anything to help

it spin. i have even seen parking brake cables heat

up in the tube under the car when a battery is rear

mounted and the ground is insufficient. I save out this

portion of harness from every car that i salvage.

replace this harness from the inner fender area with

a good used one, then replace the positive and

negative cables with factory wires. also, check the

battery for boiling over and test the alternator for

over charging.

good luck

stone

[Richard]

No one has mentioned upgrading to the later alternator that has ONLY one wire. Built in regulator and a ton more output. You will have to undo the harness to repair any damage.....

[Meintii]

No one has mentioned upgrading to the later alternator that has ONLY one wire. Built in regulator and a ton more output. You will have to undo the harness to repair any damage.....

I actually have a 79 320is alternator in the basement just laying around. Should I go ahead and swap it? I'd have to take it to autozone or the likes to have it tested first i suppose. What else would I need (other than the alt)?

Thanks for the help guys, I figured it was something to do with my ground from the block (I havent really found the best place to put it yet).

-Zac

[jgerock]

Zac -

Sorry you got burned wiring!

I'm assuming this happened AFTER you re-connected your alternator ground wire to the block - correct?

Those (3) wires at the plug are known to be faulty over time (and very well lubed with all the oil dumped into them).

After seeing the way some of the dual-lead negative battery cables are hooked up, I looked at my car closer. It has the main one bolted to the starter bracket (on the block) and a shorter, smaller lead connected to one machine screw holding the voltage regulator to the fender. Since your battery was relocated, I cannot remember how your ground cable was done inside the engine compartment.

[Beaner7102]

Also did you disconnect the battery when on the charger? You should never charge a battery with both terminals still connected to the car. Always disconnect one.

That could have been the cause for them smokin' wires. Beaner7102