I have a 2003 Monte Carlo SS. I have been having this problem for a while, but now seems to be permanent. While the car is running the battery is getting drained. Had the alternator checked and it is fine. It is not a constant drain. I can see the volt meter dip below center line then go above center line while the car is running. Lately has been staying below center line more than above. The battery is only a few weeks old and have needed to charge a couple times. Has anyone had this happen to them? Solutions?

 

Check your grounds, I had same issue and it was the ground under the battery that was rusty/dirty and not making good contact. Also the alternator grounds with the bolts so make sure that's all clean. Make sure all connections are clean and tight.

Was the alternator bench tested or tested on vehicle? I still wouldn't rule out the alternator starting to go bad.

 

The alternator was bench tested. When tested on car, failed. When bench tested, passed 4x. I will check the grounds next. Thanks for responding.

 

sounds like a wire connection issue then for sure. check the grounds and all power connections to the alt also.

 

where was it bench tested? also, if you have a multimeter (DVOM), if you switch it over to ac voltage, and touch the battery terminals with the car running, checking for ac voltage, if it's over 1/2 a volt, you've got a bad voltage rectifier/regulator... lastly, with the vehicle cold, take off the radiator cap, and start the car with one test lead in the radiator fluid and the other to a ground and check for voltage. If over 1/2 a volt, change fluid.