Alternator?

the lights dim and brighten with the engine rpm? As far as the belt. Nah, you have a serpentine belt they usally dont slip. and if they do you notice other things as well.. (ie: power steering jercky, temps higher then normal, etc)

you mentioned you have an aftermarket stereo installed.. Anything else, like an ampflier? if you do, your Altenator may not be pushing out enough power at low RPM. if that is the case you need to get a bigger Alt. Bottom line. if you see this happening run your car to the garage and have the Charging system checked..

they will check the alt voltage and amperage.. Could also be something as simple as corroded battery cables.

Check the light in the dark (all interior lights out) while the engine is being reved. If it lights dimly then the alternator is going south. If not, it could be going south or not -- hard to say.

Dan and Charles, A good test for an alternator that does not involve the dash light is to load the system. Do so by turning on the high beams, A/C, rear window defogger, radio and ... then see if you have more or less than 12 volts at the battery when you rev the motor to about 2000 rpm. You should have at least 12 volts or power is coming out of the battery. Expect 13 or so volts for a successful test. As the an alternator get more and more miles, the brushes wear and do not contact the comutator (spelling ?) as well.

chuck s.

Dan Hicks wrote:

thats a good test for voltage but you also have to see if the amperage is up to spec.. you can push 13.5 volt s which is good. but if the ampers is too low you wont charge at a rate to keep the battery supplied.

Joe, Just like what Dan here wrote, with the load being all of the accessories like the the headlights and rear defroster, a bat- tery voltage > 12V can not be maintained unless the alternator is delivering the current. There was a subsequent post from Dan that also mentions other alternator problems of a bad diode or bad coil.

I maintain that the > 12V voltage test will spot many of those as well. As crude as a test as I may have described, it is possible to do a just a simple meter. And one does not have to remove the alternator! Like a weightlifter, he (or she) can not perform a lift with an injury.

chuck

ps: Yes, the tester that many auto stores have is more "precise", but you have to remove it to test there.

Dan Hicks wrote:

Exactly........

You should switch your signs though.......should be < 12 volts (for less than

Whups........disregard my previous post about the signs.......I read it wrong the first time.......