dickk

6/11/07

My mother-in-law's 94 Cutlass has eaten 3 alternators in 40,000 miles. She bought the car new and had the first failure after 2000 miles. It was replaced by the agency with the OEM alternator. The same thing happened at about 20,000 miles. The most recent event was just as turning into the freeway entrance - it's getting dangerous. Apparently the alternator quits and the car continues to run on the battery for a spell. Finally the fuel pumps stops from lack of voltage. One can watch the fuel gauge go dead at the same time. It will start with a jumper but dies as soon as the jumper is removed. In each case the alternator has been replaced with OEM parts by the agency - their only comment is to replace it. I need a permanent fix - any suggestions (besides selling the car)?

Oldsguy

Ground wire from the battery to the block. Positive wire from the battery to the alternator. Either one of those might be faulty. I don't know how the agency decided the alternator was bad but they might have mistakenly troubleshoot to the alternator instead of the real problem (that's called shotgunning). Anyway, take a closer inspection of those wires, if you find ANY green corrosion on either one or a bad crimp on the lug ends or a loose nut on the block, that might cause you trouble. Now if the car is REALLY eating alternators, I don't know he solution to that, maybe the crank pulley is misaligned with the alternator pulley and causing undue bearing wear on the alternator, just a guess.

joe_padavano

Is this by chance a CS130 alternator? Ex-wife no. 2 (don't ask) had a 92 Buick GS (same W-body platform as your Cutlass) and the car would also eat alternators. I went through three before finding a service bulletin about the problem. On the V6 cars, the CS130 is only mounted through the forward frame of the alternator, but the electronic voltage regulator is in the rear frame. The housings are aluminum but there's an iron core for the stator winding in between. The problem is that corrosion builds up between the aluminum and the steel, ruining the ground path for the regulator and eventualy killing it. The fix is easy - run a ground strap from the rear of the alternator housing to the block. I did this and the problem was solved.

dickk

6/15/07

Thanks for your comments. I have been told that the alternator was originally designed for 100 amp and then "re-labled" for 140A. The second alternator did expire in the bearing. I still have the core for the third failed alternator. As Joe suggested the front part of the alternator is aluminum and bolted to the engine for a ground connection. The regulator is contained on the back aluminum part of the alternator and is separated by the laminated iron stack of the alternator. However, there are three bolts that tie the front and rear aluminum sections together which should electrically bridge any corrosian areas. I did measure the resistance between the front and back using a digital multimeter = less than 0.1 ohms. I'm pretty sure the failure this time is in the regulator. I intend to dig it out and measure the components.

The alternator does run hot. Just after the recent failure it was too hot to keep my hand on it even though the car was only in operation for 5 minutes before the failure.

Another possible cause is the positive battery cable that ties to the side mount terminals of the battery. The washer stack under the bolt was not assembled correctly so that the cable could be rotated even though the bolt was as tight as possible.

In any case, thanks for your suggestions.