92 Lumina, Bose edition. Starting the car is fine, I have the higher rated battery installed, and when the car is first started, the battery meter shows more than enough power, up to the 14-16v area (most likely due to the higher rated battery). I can drive with normal power with only my lights and stereo (custom stereo installed with subs/amp/capacitor) without losing power. I would also like to note that the issue started before i had a stereo installed. Applying the brakes drops the power level shown by at least 3-4 v, even if that is the only thing being done, no lights, no stereo, nothing. Sitting at a stop light my battery level drops to 8v area, or one line above the red line on the voltmeter.

The alternator is fine, the battery was unhooked and it ran just fine.

Using heat/air, rear defrost, or turn signals also drops the power, and as a side note, my turn signals no longer blink, but hazards work just fine. I searched for a switching relay but couldnt find one for the life of me.

If anyone can point me in even a general direction, it wouldbe greatly appreciated, as I have gone through 2 batteries now in 6 months or so.

 

I would replace the voltage regulator, they cost around $30.00. The relay for the turn signal is under the drivers side kick panel. If I remember correctly mine was right by the steering column.