My air hasn't been working for a while, but today while I was sitting at a stop light, I turned it to MAX just to see what it would do. As soon as I did, the car immediately shut off. I put the car back in park, and it started right up. I tried again in a parking lot, and the engine started to shake really bad so I just turned the air off before it completely shut off. Any idea what would be causing this?

 

you should check to see if the a/c pulley is spinning properly when the clutch is engaged, cause my friends a/c compressor siezed up and the pulley wouldn't spin at all when the a/c clutch was engaged

 

Bad alternator maybe? I also agree to check the AC pulley first.