Battery light issue

I have an '98 cavalier and 2 weeks ago the battery light came on and the car died, I then bought a new alternator and installed it, the car drove for 2 days and then the battery light came back on! I took the battery and the alternator in to get tested, both came back good. The question I have is, if both the battery and alternator are good, and the battery light comes back on, what could the problem be? :banghead:

you should check belt tension and wires for excessive corrosion

Clean the battery terminals and make sure the engine ground is good. Also wiggle the wires and see if the alternator stops charging at some point... could be an open wire somewhere.

Hi,

Mine is in for this repair as I type. The Alternator normally outputs 13.8VDC to the battery, but it is told to turn on and off by the PCM. There are leads running from the alternator to the module, and also to many - many other points in the engine compartment. The alternator is likely fine. The battery is likely fine. Some control wires have likely corroded to the point of short or no connect.

Good luck with it, and don't assume that all GM's are of poor build quality because of this - you have the ability to repair yourself and don't work as good as you did in 1998.!