new battery prolem Options

[Cormudgen]

Ok, so my battery light went on sometime last week. I went to autozone and they test my alternator and my battery. verdict is that the battery is weak(bad cell maybe) but the alternator is fine. ok, i go to wal mart and buy a new battery. (the 29.99) "Autostart" battery. put it in and the light continuse to stay on. drive around a lil and it is still on. i decide to drive to autozone again and get them to test it. the battery and alternator both read good this time. he mentions that i may need 15 min to clear my ecu for the light to go off or i cuold simply drive around for a little while. i then drive around for 20 more min and park it. take the postive off my battery for about 20 min. put it back on, and the light is still on. anyways i'm home now and the postive terminal is off, going to attempt to let it sit overnight. any suggestions?

thanks
cormudgen

[GeEkBoY]

The battery light comes on when the alternator is not charging. If your car is not running, but the key is switched on, the battery light will be on. The threshold for the light is somewhere between the 14.7 the altenator produces and the 12 that the battery puts out. They do this so you will have warning before your battery is dead.

It sounds like your altenator may be starting to go or the sensor is toast:
How many miles since the altenator was replaced?
Was the voltage on the altenator checked on the car, or bench tested?

If the alt. was bench tested, that is done at no load, when you load a marginal altenator, the voltage output drops and that could cause the problem. The best way to test it is with a voltmeter on the car while it is runnuing like 96STcoupe suggested.