I have a 5.3 liter engine on a 2001 sierra 4wd. If I run the heater at high for more than a minute, it will not turn off. I am able to redirect it to the floor or defroster. The only way that I have been able to make it stop is to stop and turn the truck off for about ten minutes. Now the heater will function normally again, unless I turn it up to its higher settings again, in which case the problems starts again. The engine coolant levels are correct, the engine is not over heating, and the AC works correctly.
Dec 31, 2007 at 3:15 AM