Thanks again to everyone for all the usefull insight. I couldn't have done it without your help. It was the mono valve (heater valve), replaced it and the heater worked like a dream. Took less than an hour, hardest part was getting to it. The Bosch part cost me $103, and that was it. The dealship wanted over $800, they said I needed a new climate control unit, sure glad I didn't go that route.