Edmunds Answers

Voted Best Answer

  • avatar MrShift@Edmunds 01/16/10 9:25 pm PST

    1. Low coolant level

    2. Air in cooling system (did you drain it recently?)

    3. non-functioning heater valve doesn't allow hot coolant to enter heater core.

    4. non-opening blender door to direct heat to the passenger compartment

    If you can feel the heater hoses, one IN and one OUT, and they are both warm, then it's probably the blending door. If one HOT one COLD, probably the heater valve. If neither one HOT, then probably low coolant or air in system.


Answers

  • MrShift@Edmunds 01/16/10 9:25 pm PST

    1. Low coolant level

    2. Air in cooling system (did you drain it recently?)

    3. non-functioning heater valve doesn't allow hot coolant to enter heater core.

    4. non-opening blender door to direct heat to the passenger compartment

    If you can feel the heater hoses, one IN and one OUT, and they are both warm, then it's probably the blending door. If one HOT one COLD, probably the heater valve. If neither one HOT, then probably low coolant or air in system.


  • wdhyte 01/17/10 11:47 am PST

    funny...I just had the exact same problem in my 2001 F150...checked the coolant and it was fine...felt the upper return hose from the radiator and it was barely warm so I suspected it was the thermostat...went down to autozone and got a new one for under $10...put it in (about 30 min job)...voila! upper hose was getting much warmer and heater was cranking in the cabin. I'd also noticed the eng temp guage was barely coming up off the bottom tick mark of the guage scale.

  • MrShift@Edmunds 01/17/10 12:05 pm PST

    A bad thermostat is possible but the reason I didn't mention it is that usually a bad thermostat that is sticking closed will cause the engine to overheat.

    But sure, worth a shot.

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