Electrical Problems- Caught my car on fire, New Info- please help!!!! (thanks for input so far) Options

[tornik550]

I am getting fed up. I have been posting a lot of different electrical issues lately. I am super confused. Here is a the summary of what has happened.

I have been running my car without an alternator since I rebuilt the engine. A few months ago, I installed a known working alternator (it didn't come with the little black resistor that is inside of the alternator so I took one of another (non-working alternator). Car started and ran fine. Voltage was around 13.2. Was driving around the neighborhood, had a huge amount of smoke from the engine bay. The wire from the alternator to the starter was torched.

Thinking the alternator was actually not good, I got a new alternator (my friend got it for me for free). It too didn't have the little black box so I took the one out of the other alternator and installed it in the new one. I tried to purchase a new one however they are no longer available. I also purchased a new alternator. I installed the new alternator and my fuel pump started to only work intermittently. Thinking that my fuel pump was simply bad, I just hooked up a different pump that I had. Once I got the "broken" fuel pump out, I hooked it up to 12v volts and it ran for a few seconds then died. Tonight, I tried the same thing except running gas through it and it ran however the pressure was low.

Since I thought that my problem was actually the fuel pump, I went ahead and reinstalled the new alternator. I was driving around the neighborhood for a couple of minutes. Ran fine. Parked it in the garage. When back and touched the alternator to starter wire to see if it was hot- it was not overly hot. I decided to make some timing adjustments. When I turned around to get my timing light, the wire from the alt to starter caught fire!!! I had a fire extinguisher right there. I put it out an inspected everything. It looked exactly like what happened witht he original alternator.

I have no freaking idea what is going on here. Any ideas?

[Spoke]

Not sure what is going on, but the wire melting from the starter to alternator melting I would think is current flowing from the battery to the alternator.

Only the battery has the capacity to produce that much current to melt the wire.

There isn't much between the wire and the alternator except the alternator.

The alternator would not be able to produce that much current. The diodes in the alternator would fry before the wire does.

So this points to some type of short circuit from the wire to ground. Check the cover on the back of the alternator.

[Chris Pincetich]

I caused a fire in my 914 too
(IMG:style_emoticons/default/blink.gif)
wire direct from battery grounded by accident due to lack of rubber grommets, wear and tear, insulation breach etc.
All those amps into one wire w/o any fuse or relay = melted, fire
BTW, i read this board all the time before buying my 914 and already had a fire extinguisher in the car, ready for to halt any potential "car-B-Q"

I agree with above statements: it is likely your battery that over-juiced something

Porsche engineers were smart. Rebuild what they created, and you'll be fine. Skip stuff, and well, you know...

Good luck (IMG:style_emoticons/default/beerchug.gif)

[tornik550]

Not sure what is going on, but the wire melting from the starter to alternator melting I would think is current flowing from the battery to the alternator.

Only the battery has the capacity to produce that much current to melt the wire.

There isn't much between the wire and the alternator except the alternator.

The alternator would not be able to produce that much current. The diodes in the alternator would fry before the wire does.

So this points to some type of short circuit from the wire to ground. Check the cover on the back of the alternator.

I checked the cover and I did not see any major issue. This sounds far fetched but is it possible that the wire from the alternator to the starter could arch from wire to the tin- eventhough the wire insulation is intact? Since it was just installed temporarily, I did not install the grommet between the wire and tin. That is where the wire was most damaged (the copper was actually melted at that point) on the first and second alternator. I am certain that the insulation was intact.

[tornik550]

I caused a fire in my 914 too
(IMG:style_emoticons/default/blink.gif)
wire direct from battery grounded by accident due to lack of rubber grommets, wear and tear, insulation breach etc.
All those amps into one wire w/o any fuse or relay = melted, fire
BTW, i read this board all the time before buying my 914 and already had a fire extinguisher in the car, ready for to halt any potential "car-B-Q"

I agree with above statements: it is likely your battery that over-juiced something

Porsche engineers were smart. Rebuild what they created, and you'll be fine. Skip stuff, and well, you know...

Good luck (IMG:style_emoticons/default/beerchug.gif)

Did not see this before my last post. SO could simply not having the grommet be an issue?

[Spoke]

Are you saying you saw melt damage at the tin? Was the wire damaged from the tin to the alternator? I think you found the issue.

BTW, 12V is not enough voltage to cause an arc across an air gap. However, if the insulator on the wire is damaged, touching the wire to the tin will cause immediate overheating and wire and insulation melting. Basically, you're welding with media that isn't designed for welding.

[tornik550]

Here are some pictures of the problem areas. I do not recall if the tow melted copper areas were positioned at the tin or the yellow wire fromt eh relay board to starter. I had this issue with my first alternator.

All of the white/yellow dust is from the fire extinguisher.

[tornik550]

I do not see any burnt area on the tin. The stater end and alternator end of the wire was the least charred.

Is it possible that if the Alternator to starter wire were to touch the yellow wire to the start- could that cause this issue- eventhough the insulation on both wires was intact?

I am certain that the starter wire to alt wire insulation was intact- it was a brand new wire with almost no miles on it.

[Valy]

It's obvious that this is a short of some kind. Could be that some other wire inside the alternator jacket is melting it's jacket first and then touches the wire you've seen on fire. I'm just speculating here.
this is too complex and dangerous to solve over the forum.I strongly suggest you have a potent electrician look at your problem before you burn the car.

[tornik550]

It's obvious that this is a short of some kind. Could be that some other wire inside the alternator jacket is melting it's jacket first and then touches the wire you've seen on fire. I'm just speculating here.
this is too complex and dangerous to solve over the forum.I strongly suggest you have a potent electrician look at your problem before you burn the car.

I agree about te safety issue. Unfortunately we only have impotent electricians around here-lol. To address the safety issue, I simply removed the alternator. I really don't need one. I don't drive far so I just charge te battery each night. I would still like to figure this issue out just for curiosity's sake- even though I'm not planning on using the alternator anymore.

[Mike Bellis]

The battery wire at the alternator fed the short. Follow the burnt wire to wherever it started to melt. Looks like a direct short to ground. Pinched or chafed wire to the chassis.

Just another reason I run a master fuse and disconnect switch on my car.

[JeffBowlsby]

Looks like a direct short to ground to me too...

[Mike Bellis]

BTW, the alternator charge wire on a 914 normally does not go directly to the starter. It goes directly to the battery.

Electrically this is the same circuit but the wire has to travel through the tin to get to the starter. Perhaps this is where you short occurred? (IMG:style_emoticons/default/idea.gif)

[Mike Bellis]

Another possibility is you caused the short at the alternator. Too many times in/out, since the wire connected to the starter, that connected to the battery... Direct short. =Burnt wire

[timothy_nd28]

I agree, that is a direct short and I'm sure your generator diodes are toast. This happened to me, when my fuse box broke and shorted to chassis ground. I don't recall a wire going from the altenator to the starter. Keep looking for other melted wires, and you should ohm out the relay board

[Mike Bellis]

Looking back at the ring terminal... Looks like shrink tubing. Not factory Porsche. When you fix it, run the alt wire to the positive battery terminal.

You don't need to charge the starter anyway...

[JeffBowlsby]

Last I checked the big red cable in the alternator harness runs from the alternator to a lug bolt on the starter solenoid shared with the battery+ cable. Stock factory set-up.

[Tom]

tornik550,
Looks like your alternator wire shorted to ground! It would not have burned like that if it shorted to the yellow wire. When I had my engine out, I replaced that alternator wire because it was hard and brittle. I expect yours was the same prior to the fire. Insulation loses it ability to insulate over time and your changing the alternator probably just finally got the wire to break down enough to short and cause the fire. The issues you were having prior to the fire really indicate a problem slowly getting worse. It was the wire, not your alternator that caused this.
There is no reason for you to run no alternator. Install a tested good alternator and replace the large red wire with an 8 or 6 gage wire and be sure to use that grommet in the tin.
Tom

[rhodyguy]

long ago, early in the old club days there were a number of replacement alt problems that involved (iirc) the stud with the black wire and nut making contact with the rear alt cover. the solution was to dimple the cover outwards at what would be the the stud contact point. perhaps the smoke has obscured the arc point and once the BIG melt off started the current found a path other than the stud. your car didn't burn to the ground taking your house with it, so that is a blessing. are the alt harnesses common for all years of 4 cyl production?

k

[SLITS]

Alt harnesses are all the same AFAIK.

If a harness is needed, send me a PM. I'm sure I may have a couple laying around.