I have a 94 pontiac bonneville, was driving along and my music started to fade in and out. Got home and tried to start the car and it was dead.Took it to autozone twice alt. on the car and off the car, both times they said alt. was good. The alt. hand just lays all the way down. I even tried another alt that I know works and hand goes only to about 12 and slowly goes back down. I need help tis car is driving me crazy.

you clean the big wire connections? clean the battery terminals? whats the voltage at the battery?

yea the wire is clean, i checked the battery connections and when i unhook the positive cable the car cuts off but the alt is good.

Check the car side of the ground wire?

sorry for but where is that ground at? and can it be a relay or something?

Follow the ground wire from the battery to wherever it lands on the car. Make sure that the connection is clean.

checked that and the connection is clean

And the voltage of the battery is? And how old is the battery?

I dont know the voltage of the battery and its about a year and a half old, but when I take the positive cable off shouldnt it stay running? and doesnt that eliminate the battery?

Im assuming you double and triple checked the lines to and from the alternator.