This problem has been going on for a while. The heater is stuck on. The mechanic replaced the defroster/heater control board (I think it was a salvage part, not a new OEM board) but no luck. [:@]

I was told by a friend that it could be rusted heat exchanger valves, but they move freely. I'm thinking either the control board or the cable is stuck somehow.

Anyone have any suggestions?

 

Have someone crawl underneath while you operate the controls and see if the gates are moving. It is a mechanical link, via a cable, so they can't really not work if the cable isn't broken, and the valves arent rusted.