I have no idea why you have posted a car question in the Satellite Receivers area. However, I used to work for a car dealer. It sounds to me like classic case of a stuck coolant thermostat. The fix is to replace it.
T
February 2010
I can answer this question...
MY HEATER ONLY BLOWS OUT COLD AIR EVEN WHEN ITIS ON HOT IV CHECKED THE FUSE?