I have a 2000 GMC Sierra 1500 with extended cab, 4wd, 4.8 L engine with AC. My heat is blowing air that is slightly warmer than the outside air. When I first turn the blower on I get a burst of hot air and then it quickly cools down. My coolant level is good and the thermostat is good...temperature gauge is maintaining just under 200 degrees. Both heater hoses are also hot at the fire wall. I replaced the cabin air filters which were filthy, but it didn't change anything. Neither does switching from floor to dash or defrost. Changing from outside air to recirculate. Has no affect either. The AC also is working fine. Am I missing something? Any ideas? Thanks.
Last edited by robwaldron66 (11/4/2011 11:46 AM)
The way you explain the problem it sounds like you probably have a temperature blend adjustment problem in the heat door which could be an electrical connection problem or not being adjusted properly.
With the coolant temperature being at 200 degrees, the heater hoses being hot at both hoses shows the thermostat and heater core appear to be working properly.
There is a service bulletin on aluminum heater core and radiator flush procedures, it is 05-06-02-001 dated 7-16-2007. It states a procedure to flush the cooling system the proper way. Contamination of the coolant could cause a blockage in the heater core and or the radiator. This would be investigated if everything else checks out.
There is also another service bulletin on this problem it is 01-01-39-007 dated 1-1-2002. It states the proper repair procedure to the wiring problem to the A/C system temp/mode change problems. You can get the full service bulletins at ALLDATAdiy.com.