Alternator pulley bearing replacement

Yes, parts can be replaced individually, but that will be strictly a do-it-yourself project. No professional will do this for a customer's vehicle because they can't insure the quality of the repair. If a part fails or something goes wrong, they have to do the work all over again, for free. Also, just the labor charge, not including the parts, to do the job this way would be much higher than the cost of a rebuilt generator.

The next problem is this is by far the worst generator design ever developed. Besides the very high failure rate, it is almost impossible to get it apart. You should have less trouble if you just replace the front bearing, but it doesn't make sense to tear it apart that far, then fail to replace the other common items. There are repair kits available at most farm and home stores. They include the voltage regulator, diode block, brushes, and one of the bearings.

Unlike GM's older design from 1986 and before, which was a pretty good design, this one has no test point available, so there is no way to tell if the voltage regulator, brushes, or diode block have caused a failure to charge. Also, just to get those parts removed is a lesson in frustration, and requires desoldering three wires at the same time, through slotted holes in the housing. Most of the time you'll break the flimsy tabs off the diode block, then that is junk, but you still don't know if the other parts are defective. To prevent having to do the job over, all the parts get replaced. By the time you're done, for the sake of your sanity, you're better off buying a professionally-rebuilt generator with a warranty.

The bearing problem is the second most common problem. The biggest problem is the failure to charge, and that can lead to multiple repeat failures. For future reference, you should be aware that due to their design, these generators develop huge harmful voltage spikes that can destroy the internal voltage regulator and diodes, and interfere with computer sensor signals. The key component in damping and absorbing those spikes is the battery, but as they age and the lead flakes off the plates, they lose their ability to do that.

It is not uncommon to go through four to six replacement generators in the life of the vehicle. To reduce that number of repeat failures, always replace the battery at the same time, unless it is less than about two years old. The old battery will work fine in an '86 or older model.

The standard generator for your car is a 140-amp unit. The parts that come in the repair kits are the same for most GM generators. The different current ratings come from the stator winding. That's the stationary coils. Those rarely need to be replaced.

If you decide to replace the generator, don't be afraid to shop around for the best price. A friend with a '99 Suburban replaced his generator for the third time, and that is when he found one for over $200.00 with only a two-year warranty, and a different one from a different company with a lifetime warranty for $50.00 less.

No preference. I go by the best value. If it's a trade-in for a used car dealer, the warranty has little value. They're more concerned with cost. If it's for a car you're planning on keeping for at least a few more years, you're better off with a lifetime warranty, but even that is a potential variable. For most rebuilders, a lifetime warranty is only honored for the original purchaser, and it doesn't transfer to the new owner if you sell the car. You can find some that do transfer. The rebuilders that offer that are hoping someone is going to lose the receipt or paperwork, or the car will end up in the salvage yard.

There are also differences in what parts are replaced. All rebuilders clean everything up to look like new from the outside, but some only diagnose the defective part and replace that, while others don't bother to diagnose anything. They automatically replace all of the common failure parts.

If you or I were to try to disassemble this generator to get to the voltage regulator and brushes, it's almost certain we will break the thin tabs off the diode block. There's no way to repair that damage other than to replace the assembly. That's why a new one comes in the repair kits I mentioned. There is also no easy way for us to test the voltage regulator like there is on Chrysler systems and on older GM and Ford systems. You wouldn't want to take a chance on it, so it gets replaced too. The rebuilders have a way to test those parts after they're removed, so they might reuse the old regulator.

Another variable is many of the aftermarket parts suppliers find ways to improve on high-failure parts, so, for example, they might design in more aggressive voltage spike immunity for their voltage regulators, or they might change something to reduce the severity of those spikes. This is why very often an aftermarket replacement part can be superior to an original one. We see this all the time with Ford steering and suspension parts.

The bottom line is there seems to be little correlation between price, quality, and length of warranty, so you have to decide which one is the best value. Most of my daily-drivers are old, rusty cast-offs from relatives, then I drive them until it might be safer to walk back home, then I drive them some more. I don't run into many electrical problems, but when I do, I'm more concerned with the warranty, because, like with my last Grand Caravan, I drove it until it got so rusty, the carpet was the only thing holding the front and rear together! Most of the parts I bought for it over the last few years can be transplanted onto my current rust bucket, so the length of warranty is what I look for.

Don't overlook a used generator from a salvage yard. You'll pay a lot less, but if it comes with a warranty of any kind, expect it to be for only 30 or 60 days. They get a lot of these in, but most get thrown into big barrels without regard to testing, then they're sold by the barrel to those rebuilding companies. Your car is old enough that there is going to be less and less call for a used or a rebuilt generator that fits it, so the cost at a salvage yard is likely going to be less than for generators for newer models. You're less likely to find that drop in price at the auto parts stores.