Question about 1996 Isuzu Trooper
At cruise speed, the output of my '96 Trooper's alternator will drop from about 14 volts down to 10-12 volts, then it will jump back to normal without apparent reason. This sometimes happens during acceleration, as well. I'll check connections, but does this problem sound like a diode failure?
It sounds like your alternator could be on its way out
Posted on Feb 11, 2009
It could be a number of problems, pretty much all of which would go in the alternator category.
Voltage regulator, diodes, etc. It's a warning sign, so get it taken care of soon. As long as your BATTERY itself doesn't get less than 12 volts, then you'll still run OK. But you don't want the alternator dying at nighttime with you stuck trying to get home while burning all your headlights, heater motor, etc.
Once it gets so dead, it'll eventually not have enough power to keep the engine going, then you be dead.
You can have the alternator taken off and tested, but it sounds like you should just get a new one.
The parts store will often offer a "new" alternator, or a "new rebuilt" alternator. The prices difference is usually drastic, so it just depends on your experience with rebuilt parts. They'll both have warranties. If you chose a rebuilt one, they'll need your old one for a core charge.
You could also try Ebay. Sometimes they'll have a really good deal on a new or rebuilt one that's just sitting on someone's shelf.
Depending on your engine, it's not too hard of a job to do. Just make sure you disconnect your battery first and get the "+" and "-" in the right spots on the alternator. You'll probably have a serpentine belt to remove, then a few bolts for the alternator, then connections going to your alternator. If you're lucky, your alternator may be sitting on the topside of your engine rather than being tucked down in a hard to reach area.
Posted on Feb 11, 2009
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