the last time I had the Bonneville in at the dealer for service the mechanic noted the alternator was making a bit of bearing noise (but still charging fine). As far as I know it is the original. So I purchased an ac delco rebuilt alternator over the counter from the gm dealer and this weekend I put it in.

But it doesn't work. It does not maintain proper voltage (voltage is low). My battery is good (recently replaced - it was due) and I'm confident the rest of the electrical is good because old alternator was working fine (just bearing noise). I checked voltage from alternator case to ground to confirm good ground circuit and checked voltage from positive post on alternator to positive post on battery to confirm good battery cable.

Pulled the rebuilt unit out and put the old one back in, voltage back to normal.

The weird thing is the rebuilt unit must be doing something, cause it was generating a huge amount of heat, ran the engine for just a couple minutes while doing the voltage checks and the rebuilt alternator was just frying hot - it was actually smelling like it was melting inside. when I went to pull it to put back the original one, I had to wear mechanics gloves and I could still hardly hold it long enough to pull it out and put it on the ground, it was so hot.

I've already talked to the gm dealer, they will bring in another rebuilt one and exchange it, has to come from Edmonton, should be here by Wednesday.

Anyone else had any similar experiences? thanks, Mike

Must be one of those once in a blue moon flukes. Bad parts do come off the line occasionaly. Good thing it happened right off the bat and not 500 miles from the nearest shop at 2AM.

for what it'* worth, which is I guess not much, the rebuilt one came with a little test report card which claimed each rebuilt unit is individually tested before it is shipped.

I just replaced the alternator in my truck, got one from O'Reilly'* with a life time warranty. You can't really go wrong there. I would assume you could find something with a lifetime warranty for the Bonne to.

This. I buy almost all my parts from O' Reilly'*, for this reason. Almost everything sell has a lifetime warranty and is priced right.

Returning the bad rebuilt alternator for a full refund and then going elsewhere was not an option according to the gm dealer. Since the part had been installed and used it could not be refunded. They exchanged it for another rebuilt one and it had to be done as a warranty claim (the delco rebuilt alternator has a one year warranty). They took a quick look at my car to confirm there wasn't something else wrong that could have caused the alternator to fry itself (I don't think there'* anything else to the charging system other than the alternator and the battery) so it was just more paperwork for them but unfortunately the 1 year warrantly period doesn't reset.

the second rebuilt one seems good, proper voltage and no smell, still seems to run very hot but dealer says that'* normal.

1 year warranty from GM. Limited Lifetime from a major auto parts store. Something doesn't add up here.

The problem with Rebuilt alternators is the windings are usually original, with bearings and hopefully the voltage regulating chip replaced. (And often not OEM quality)(Even by AC Delco rebuilders) Large Auto Chains "play the spread" and give Lifetime Warranties to get you business. GM figures your a "Dealer Service Person" and just looks at the maximum profit line. I don't think quality is any different between the two. One just covers the odds if it eventually fails before you get rid of the car. I always pay the little extra and go lifetime.

I've never bought replacement parts from the dealer LOL, because I NEVER go to the dealer for work unless the car is under warranty.

I do the work myself as long as it'* within my abilities, but for the parts that wear out and should be replaced with new/rebuilt I still buy most of them over-the-counter at the local gm dealer parts department. We don't have as many alternate choices here in western canada and I have an account so I get them at a reduced price. I appreciate other peoples rides that are modded but for this car the theme I'm going for is original, so especially for parts that are visible I try to stay with factory correct or authentic gm replacements