Charging Problems

[rollin_on13s]

I have a '96 Rodeo w/ the 3.2. I have yet to pull the alternator off to have it tested, but at this point it's my next step......
Here's the problem: the charge on the battery gradually decays over a number of days. I had my battery re-charged and tested after it left me stranded last week. The battery tested as bad and I got a replacement battery under warranty. A week later, the battery has completely discharged again. The voltmeter shows really strong voltage in the mornings after start-up, but gradually the volts fall off. It's really sensitive to having any accessories turned on....the lights, A/C, even the stereo seems to take a toll on the flow of volts within the system.
It seems like a week alternator, but how would that ruin an almost new battery? My worst fear is that there is a short somewhere within the charging system.

[Ramblin Fever]

No short - just an alternator that "will" theoretically seem as if it's powerful enough - however, for these engine's it is not. It's failing - true classic symptoms.

These Isuzu's love GOOD and clear voltage, and when they sense a short anywhere in the system, they will act weird - that includes all accessories.

My advise, don't argue with it, just replace the alt - as it WILL kill a battery. Speaking from experience, myself.

Another hint - don't bother with your basic aftermarket alternator, these trucks will eat most of them alive. Try a high reputable brand, ie. OEM (from the dealership) or BOSCH. They will cost a bit, so be prepared.

Again, I HIGHLY doubt you have a short; just a fussy/dying alternator.

[rodeo02]

Yessir, sounds like a bad alt. Grab a multi-meter & see if you have 14VDC across the battery with the truck idling. Voltage < 14 = bad alt. Like Ramblin says, shoot for an OEM bosch as parts store remans are usually bad before they go in.
G/luck
Joel

[rollin_on13s]

Good info. Thanks a lot, guys.