Popped my alternator, why?

CManT1914 · Oct 6, 2005

I was driving to lunch, coming onto the access road, I nailed it and wound out 2nd to about 5600 or so. Smelled something burning all of the sudden. When I pulled into the parking lot, I noticed my voltage gauge was reading real low. I parked, popped the hood, and noticed the cable coming off the alternator is fried completely off, and it's all burnt black. WTF?? I don't know if the alternator itself is blown, or just the cable. Anyway to test the alternator? What would cause this? A bad/loose ground? If yall remember I had a problem with my negative battery cable heating up and smoking a month back. I'm sure they're related. Any ideas? My car is now out of commission, AGAIN!!

Chythar · Oct 6, 2005

Wires tend to fry like that when too much power is pushed through 'em. So, my first guess would be the gray voltage regulator on the back of the alternator. Easy to remove and replace.

The voltage would be low because the wire was fried; it won't carry as much voltage through the wire now. You could also have fried the voltage regulator at the same time. Replace both, and you should be fine.

In case you're curious, here's how the alternator and such works. As the alternator rotates, it generates voltage. The faster it spins, the more volts (and amps, but we won't get into that) it generates. Without any regulation, the excess voltage would fry your electrical system at higher rpm's. The voltage regulator is there to do what its name suggests: regulate the voltage. This guarantees that the car has enough constant voltage to run everything it needs to run.

Black95GTS · Oct 6, 2005

Chythar said:
Wires tend to fry like that when too much power is pushed through 'em. So, my first guess would be the gray voltage regulator on the back of the alternator. Easy to remove and replace.

The voltage would be low because the wire was fried; it won't carry as much voltage through the wire now. You could also have fried the voltage regulator at the same time. Replace both, and you should be fine.

In case you're curious, here's how the alternator and such works. As the alternator rotates, it generates voltage. The faster it spins, the more volts (and amps, but we won't get into that) it generates. Without any regulation, the excess voltage would fry your electrical system at higher rpm's. The voltage regulator is there to do what its name suggests: regulate the voltage. This guarantees that the car has enough constant voltage to run everything it needs to run.

It's true.... everything in your car is at 12V dc. Your alternator outputs a 13.6ish - 14.5ish ac volts. The voltage regulator is there to keep the alternator output between those limits. This is because the ac - dc converter, which is usually a diode pack, needs to have an input at those levels to function properly. If you're regulator goes, then you could be seeing a voltage out of the operable range, which results in current out of range, which results in a melted wire.

Alternator --> voltage regulator (13.6-14.5V AC) --> diode pack (12V dc) --> car

If I were you, and I know you don't want to hear it, I'd just replace the whole alternator unit. Electrical gremlins are worst to deal with, better to be safe then sorry.

- Adam

illwood · Oct 6, 2005

Adam knows what he's talking about. I also agree about replacing the whole assembly

HISSIN50 · Oct 6, 2005

Chris, you can rewire the alternator cable - mine was starting to frey at the alternator too. I just redid it and went from a 40 mV voltage drop from the alt to distribution block, to 4 mV drop. You would probably want to do this anyhow, no matter what else is needed.

The alt cable as at least one (maybe two) fusible links for circuit protection. If you start at the distribution block and trace down to about where the cable is at the side of the PS pump, you should find the links. Make sure they did not burn (hopefully they did - if your alt cable came off and touched ground, that would help save the electrical system).

As you know, you can remove the alt and have it bench tested at the parts store.

Or just redo the cable and see what happens.......LOL.

Good luck bud.

CManT1914 · Oct 6, 2005

JT, how would I go about re-wiring it? Could it be spliced? I traced it back to the fuse box, but didn't see any inline fuses or whatever. I did see that it split off, and had a plug on one side, and a terminal that a nut tightened over on the other side. It looks real easy just to swap out the entire cable, but where would I find one? I'm guessing 50resto, would they have the voltage regulator too? I might just use this as an opportunity to upgrade to a bigger alternator, due to my stereo system.

HISSIN50 · Oct 6, 2005

CHris, I will shoot you an email with how I did it and a pic.....

mo_dingo · Oct 6, 2005

A loose connection instantly creates a lot of heat and could do this. I have seen it a million times.
Scott

CManT1914 · Oct 6, 2005

HISSIN50 said:
CHris, I will shoot you an email with how I did it and a pic.....

This is why I voted JT the coolest guy on stangnet!

mo_dingo said:
A loose connection instantly creates a lot of heat and could do this. I have seen it a million times.
Scott

A loose connection at the alternator? I remember having to retighten that nut after replacing head gaskets. Maybe it worked it's way loose, or I didn't get it tight enough.

94GTLaserRC · Oct 6, 2005

This may not be it, but here are a couple of FACTS:

If the back nut holding the cable on is loose, you will get arcing (arking). This can cause what you described.

The stud that the nut goes on has that plastic piece to keep the metal of the cable away from the body of the alternator. If that metal on the cable comes in contact with the body of the alt, that can happen too.

RC

WhiteDevil · Oct 6, 2005

The same thing happened to me. Turned out the grey wire has a hole in the insulation and was grounding out and causing my alt to run real high. The main wire broke off. So i ran a new hard core wire and spliced it in right before the inline fuse(fusable link), looked real slick. Its been on for about a week and seems to workin great.

Also if you are going to do this its best to take the whole group of wires out to work on it . If you disconnect the ones on the alt side(3 of em) and then take off the bracket that holds the Coil on, and then disconnect the side that goes into the fuse distribution block and one other connection. Then you can remove that hwole section of the harness, and work on it outside of the car much easier.

Pokageek · Oct 6, 2005

Anyone know where we could just get a new set of cables for it? Resto doesn't seem to have it listed for our year.

CManT1914 · Oct 6, 2005

Pokageek said:
Anyone know where we could just get a new set of cables for it? Resto doesn't seem to have it listed for our year.

Yea I was wondering if somebody just sells replacements. I don't really have time to actually work on the stang anymore, although I can if I need to. JT hooked me up with some great info about rewiring the alternator cable for about $20, I might just go that way. Doesn't sound to hard. I did notice that the entire cable will come out of the car rather easily, so that should make things quite nice.

Popped my alternator, why?

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