Audio Systems: stereo, pep boys, auto parts store

Question
I have a 1997 cavalier which seems to be doing something weird. When i play my stereo and have the air conditioning going when i stop at a light or stop completely the stereo will go off then come back on. However, when i am driving i can have both on at the same time with no problems.. What is happening?

Thanks!

Answer
Karl,
SOunds like you are having problems with your charging system.  The slower the alternator turns, the less current comes out of it.  If your stereo is big enough (or your charging system is faulty enough) it can drop the voltage below a safe level.  You stereo is designed to shut off below a certain voltage (which is what it is doing).  A national chain auto parts store (Pep Boys, Kragen, Schucks, Checker, NAPA) will usually test you charging system for free and tell you what is wrong.  

Juan