Have you checked for a sticking thermostat, a clogged heater core or the heater control valve?
January, 24, 2010 AT 12:00 PM
Thank you! The engine builds heat, and maintains a constant temp, so im not thinking its the thermostat. But i did not consider a clogged heater core or a stuck valve, thank you! Im thinking its time for a trip to a pro to make sure. This truck has an electonic thermostat that is manipulated from the steering wheel. The air switched from defrost to heat to vent as dialed. The air cond also comes on as dialed, so the control valve or clogged heater makes sense. What does make it sound like the blender door is that it made a popping noise (according to the former owner) at random times which caused the air to turn warm.
ANY further thoughts would be extremely welcome, thanx!