Bad alternator?

[PhoebusApollo]

My car was in the driveway idling last night when the lights dimmed and the engine started doing something I can only describe as "pulsing".

I have a pretty decent stereo in the car, about 2500 watts, so it does run the alternator pretty hard, so I figure the alternator went... and the battery started dying... but if anyone has any other ideas please let me know, before I dish out $150 bucks for a new one.

Thanks

Rob

[thx247]

sitting at idle the alternator makes the least amount of power possible, if the car continues to charge the battery and plays the stereo without dimming lights when you are driving normally the alternator is fine. Most of the time people get caps or something to smooth out high loads on the alternator correct?

[Startours7]

My dad told me a old trick(don't know if it's works) Let the car idle,
disconnect the ground from the battery, if the motor dies then the alternator is bad.
If you have a mutlimeter check the volts from the alternator with the motor running. It should be 13-14 volts or so.

[VitaminT]

Originally posted by Startours7
My dad told me a old trick(don't know if it's works) Let the car idle,
disconnect the ground from the battery, if the motor dies then the alternator is bad.
If you have a mutlimeter check the volts from the alternator with the motor running. It should be 13-14 volts or so.

That works. My alt. was dead on the SR clip when I got it. When I was hearing it run before buying it we removed the negative lead on the battery and it went dead. I had autozone later check it and it was bad. BTW...for anyone that cares you can make a KA alt. work on a SR. You just have to work with it some and swap the pulleys. That is a whole lot better that having to buy one.

[PhoebusApollo]

I would try all this, but the car won't start now. It does turn over, so it's not the starter or a ground.

I guess I'll charge the battery and try again.