I have a 94 Bonneville i bought it two years ago and yesterday i replaced the alternator for the 4th time does anyone know why this keeps happening??

The placing of the alternator over the engine could be the problem so Ive been told the engine gets hot then the alternator will over heat and break down

It's best to replace the battery at the same time if it's over a year or two in age. A weak battery can over-stress an alternator, and a weak alternator can shorten the life of a battery.

Quality also means everything. Duralast is the worst. AC Delco is the best. Others fall in between. Get the right alternator and a good battery, and you'll go forever without any problems.

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Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

Absolutely!

Don't know if you've got NAPA stores, but they seem to remanufacture thoroughly, rather than just replace bad parts. We put a NAPA alternator in our own '94 a couple of years ago, and it's a champ.

As willwren says your battery has got to be up to snuff too. And while you're at it, inspect and clean up all the heavy cable connections, and especially peel way back the battery connection hoods and look for corrosion (that's also a willwren "biggie").

Remember, our '94s and older are getting "old". You have to keep getting under the hood (as well as under the car), and be continually checking components out.

Ditto on the NAPA brand rebuilds as well as new. But they'll have a choice between 2 or 3. Go for the top, or don't bother.

Also ditto on cleaning up the battery connections.

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Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

ya i work at napa haha i put rebuilts in before but this time im trying a brand new one i hope it last longer

our 93 used to eat cheap alternators too, bought the expensive one and never had to touch it again!

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2000 ssei gone but not forgotten

Current fleet:
2009 G8 v6, 2009 Avalanche LTZ, 2013 Volt