I trying to fix my wife's '99 Pontiac Grand Am GT 3.4L. I don't know if I having a bad search day but I can't find anything specific on the internet. And never fear she will be replacing it in the next few years and I think I have her convinced to buy a Ford.

I haven't had much need to mess around with alternators so I'm kind of lost at what to check for.

How do I check the alternator? It has a connector with 4 small prongs with small wires. Voltage for the three were around 7.7 milliamps wihich I'm guessing was for the guages or computer. and the fourth was at 12.18 (I think, 12.something at least). There was a bigger wire attached the the back with a voltage of 12.something coming out of it. This was with the car running at idle and revved up. Obviously too low but I'm not sure if I'm checking it right.

Where do I get a replacement if I determine the alternator is bad? I've heard the usual horror stories about the usual places. (Pep boys, Autozone, etc.) I also read that NAPA has rebuild kits. I guess it is the recitifier that normally goes bad. Seems like a pretty easy swap and I'm willing to give it a try. Anyone try this?

FYI, I'm susre the battery is good and all the goround connections are tight and free of corrosion.

Thanks

 

If you think your going to take it off anyway, I would suggest taking it off and take it to OReilly's or Autozone and have them check it for you. They will tell you if it is charging under load and I have had good luck with their alternators in the past.

 

If it never shows any more voltage than around 12, it isn't charging. It should be over 13 volts when running. You can get free checks at any of the parts stores generally. I wouldn't advise using Autozone for electrical parts though, at least from my experiences with their parts. It is pretty common for the GM alternators to take a dump like that though. About every 100,000 they tend to fail. I had one fail so bad I noticed sparks flying past my window, so I started paying attention, and my voltage was going down. I finally stopped to check it out, and the alternator actually was burning! Luckily, there was a lot of snow around, so I just put a big chunk of snow on top of the alternator...

 

Take it off, and take it in for a testing. Skip the rebuild kit, just get a quality replacement and call it a day.

 

I tried to fix one once, just had a bad diode. The fields are soldered on, so they have to be undone just to get the alternator split. It cost I think $60 to get the diodes, then the darn thing failed anyway, for another $40 I could have just bought a reman. It just isn't worth the effort to fix them yourself, unfortunately.

 

I had some problems with the alt. on my Nissan a few years back, and found it specific to that model and expensive (I think it about $140.) I bought the internal regulator for about $25 and replaced just that, it worked for a year and then the rectifier went out, it was about $40. When it quit again I had a parts car and just swapped the used alt. on, it's been fine ever since. I saved some money by redoing it myself, but it didn't hold up. But I was cash poor so it was all that was in the budget at the time. -TD

 

When the alternator crapped out on my RV, I went to a local starter/alternator shop rather then dealing with autozone, napa...etc.

I got a brand new one for $50. My ford alternator was damaged by sitting in water for a long period of time. I felt roughness when turning it by hand. It cost me $30 to have it refirbished and it's working great now.

 

The local alternator/starter electrical shop is a great idea, as they will build them better than any reman company, as their reputation is on the line. The one I have dealt with is a little more expensive, but you won't likely be taking that unit back to them, it will last longer than the factory or the remans.

 

Thanks for the help. I guess I should have checked the speciality rebuild shop. I did that I think in '96 or '97 with my '89 mustang and it has been fine ever since. I can't remember the price they charged though. I went with NAPA and got a reman for $125.00 Probably could have done better but it is our most used car and the wife was getting annoyed at watching the gas guage go down driving the 250.

Just for the heck of it she called the dealer. $310.00 for the part. Not to mention the labor ( 20 minutes for me total and that was mostly trying to get the belt back on) and the tow to get there. They could only test the part if it was on the car.

Right now its putting out 14.9 at the alternator and 14.7 at the battery. Is that a normal voltage drop between the alt. and battery? And does the voltage seem a little high?