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2001 GMC Sierra heater will not turn off

Tiny
BIGBEN76
  • MEMBER
  • 2001 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
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.
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Monday, December 31st, 2007 AT 11:15 AM

1 Reply

Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
If I understand you correctly the blower motor itself stays on high speed. In that case your blower motor high speed relay is staying energized. Try tapping on it when its acting up. If it shuts off when you tap it then replace the relay.
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Saturday, January 5th, 2008 AT 4:59 PM

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