i am going to go look at a chevy caprice tomorrow for a friend and she told me that the heater didn't work it blows air when the a/c. but the not when the heater is on. im not sure if that right. what generally causes it to go out. i am going to check the fuses and make sure there is no puddle on the passengers side. and check to make sure it was never bi passed. i mean capped off on the engines water/coolant hose fittings. is there anything else i can test. as of right now, not seeing it im leaning toward it being the Controls. Does anyone else have any other ideas?