Alternator

98 Rodeo. 6 Cylinder.

I had my alternator checked at autozone and it passed the test. After that I changed my battery because it was testing low and replaced my ground post. But at high RPM's my battery light still flickers which to me means the alternator is is not putting out the appropriate voltage and is maybe working under a light load but is not working under a heavy load.

So two questions.

1) Has anyone had an alternator pass a store test but still go bad?

2) Do my symptoms look like an alternator problem.

If it is not the alternator then I am not sure what is going on.

Both my previously dying alternators passed every normal test.

However, they did not pass the *Isuzu* test.....these trucks are VERY voltage happy, if they sense any kind of weakness they will act retarded and throw a fit....seriously! They react like a 2yr old child!

That said, what your alternator passed at, is probably what most vehicles could run safely on, but unless it's putting out a MIN 14v with the truck running and all accessories on, your alt's NOT putting out enough volts for your truck.

Also keep in mind, if it's showing less then 14v and you need a new one, look for Napa stores for good quality, or online....do NOT get just any alternator, these trucks will eat most of them within 30min or so.

I myself have the 2nd to the top of the line that Napa offers. It came with a lifetime warranty, so I never have to buy a new one again; but it ran me around $200.

Keep us posted. Have your truck's alternator rechecked with the stereo/hvac system ON while running, if it's less then 14v...start shopping around for a new one.

It's VERY normal for the battery and the alternator to either crap out together, or very close.

Thanks for the quick, detailed reply. I think you have pretty much confirmed my suspicion. The battery light flickers more when I have the lights on, radio on, A/C running, etc. The alternator passed the test on a machine at the store after I had taken it off. I am going to run my own voltage tests tonight to double check but I am pretty convinced it is the alternator.

1) yes (Advance rebuild - mistake!)
2) yes (as noted above, get a good one!)

Performing your own tests with your multimeter is better than testing it at a big box store. Heck a decent meter at Harborfreight only costs like $20. Mine has helped me plenty of times.