I hadn't made any electrical alterations to the car and one day the alt just burnt up...don't know why. I replaced it with a stock 63 amp...drove it for about 7-10 miles...burnt up the new one...just in case it was a wierd coincidence(sp?) I replaced it again...sure enough, it burnt up... I can't even begin to think of what could have went wrong....anyone have an idea? I thought about just putting on a bigger alt and seeing what happens...what do you guys think?

 

I apologize if I am being too basic here, but is the battery fully charged? An alternator is a "battery management" device, not a battery charger. If the battery is near death, the alternator will have a tendency to put out all it can all the time and heat can do it in. Check all wiring for chaffing, ensure you have a good engine to chassis ground and charge the battery fully. It wouldn't hurt to have the battery load tested - I just had a similar problem with a Buick - engine started fine, but would kill alternators: took the battery to Auto Zone for testing. Load tested OK but would not recover well - meaning, under load it stayed above 10.2v - after load was removed it stayed at 10.5V. would not return to 12V. Alt kept givin the battery everything it had & would fail in 2 days. Replaced battery & been fine since. BTW, picked up last Alt at Junkyard for $5 - still working fine!
Corky

 

Man I am getting more mileage than you out of mine but I have the same problem, it will work fine then all of the sudden it has a variable in my voltage gauge from 8-9 volts then it will go to 13-14, eventually it dies, your sound like this?

 

Corky may very well be right, and if so then the battery should become warm, or even hot.. I must say I am apalled at the idea that a generator is so badly designed that it burns out from running at full load for a little while, but I have seen it happen in a boat where the old one had been exhanged with a hi-amp unit. It had a bigger pulley and this was obviously bad for its longevity. A fan moves air as a function of the square of the rpm, so one solution to your problems might be to exhcange the pulley with a smaller one. In addition to the added cooling there is also the benefit of less wattage being used in the field winding (rotor) because of the increased rpm.

 

no modern air cooled automotive alternator can run for very long at or near max output, it over heats them. thats why some of the newer cars come with liquid cooled alternators.
with the huge electrical loads of some of the new cars, the factory has the alternator output turned up so high they won't live without the extra cooling.

 

Actually the first time I replaced the alt I went ahead and had my battery tested. everything was fine. checked all the body grounds, also good...even replaced 'em...still nothing...I'm baffled...

 

you tested it, but did you recharge it before driving the car?

 

I had a similar problem that also started randomly when I first bought my car.. It turns out it had a short circuit in the thick pink wire that comes from the battery the alt. connector.

 

I did have the battery slow charged before I put it back in the car. I think you might be onto something sicc87. when I bought the car a push button start had been instaled...I've long since removed that, but it used that wire. I'll check it out. thanks guys.

 

J, are you replacing these alternators with those from a reputable remanufacturer or are we talking VatoZone units here?

Is it the CS-130 design?

Is there any appreciable voltage drop between the output terminal of the alternator and the battery while charging?

 

The first one came from a friend who works at autozone, although the alt itself camefrom Napa. after it burnt up I did pick one up from autozone and it did the same thing. and yes, there is a very noticable voltage drop during charging.