1999 GMC Sierra Heater not kicking out hot air.

1999 GMC SIERRA
19,400 MILES • V8 • 4WD • AUTOMATIC
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ZACHOYLEACH
  • MEMBER
  • 1 POST
I have recently been having problems with getting hot air out of my heater vents. I thought it might have been a stuck thermostat, so I replaced it. Still nothing. The coolant level is correct and I think the water pump is operating correctly. It seems to have good circulation and it isn't leaking a bit. The heater core isn't leaking either. The vehicle gets up to the proper operating temp just as before, but still no hot air. I was wondering if I should flush the system, but the anitfreeze looks just fine. I'm a missing something. My next step is the replace the water pump. But I'll probably wait until I know something for sure. Oh, and the temp control is working just fine also. Not, faulty.
Apr 10, 2008 at 11:34 PM
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RASMATAZ
  • ASE Certified Mechanic
  • 75,992 POSTS
  • ASE Certified Mechanic
Could be the heater hose and heater core clogged up/air mix/blend/mode doors not opening or a problem with an actuator or vacuum-
Apr 11, 2008 at 1:53 AM
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