Heater inop

2001 BUICK LESABRE
185,000 MILES • 6 CYL • FWD • AUTOMATIC
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SHARBUT
  • MEMBER
  • 2 POSTS
I have a 2001 Buick LeSabre-Custom, v-6, 3800 series engine.My heater isn't working. It blows cold air. Engine thermostat has been changed. Upper radiator hose is hot after being driven. Any ideas on what the failure might be?
Nov 25, 2010 at 10:46 AM
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ERNEST CLARK
  • ✓Experienced Mechanic
  • 1,730 POSTS
Your upper radiator hose is supposed to be hot, and so is the bottom. When the thermostat was changed, did they bleed the system of air? Because this can be your issue if air is trapped in the heater core.

If that's good, then your issue is either a stuck control shut off valve, blocked heater core, Stuck/broke blend door inside the HVAC unit or a leaking vacuum line/solenoid in the HVAC unit.
Mar 22, 2021 at 5:54 AM
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SHARBUT
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  • 2 POSTS
How would I determine the "stuck control shut off valve"? And where is the shut off valve?
Mar 22, 2021 at 5:54 AM
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ERNEST CLARK
  • ✓Experienced Mechanic
  • 1,730 POSTS
The shut off valve is located on one of the small diameter coolant hoses that enter and exit the firewall on the passenger side. It's a small metal valve with a linkage hooked to it. Once your engine warms up, have someone turn on the heater controls (high) and watch the movement of the valve.
Mar 22, 2021 at 5:54 AM
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