Heater not working after replacing thermostat
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Thread: Heater not working after replacing thermostat

  1. #1
    NECO Member
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    Heater not working after replacing thermostat

    Ok, here is what happened. My and my girlfriend were out 2 nights ago drivin around when we noticed her heat wasnt working. We then noticed that the car was overheating. Si we headed back home to diagnose the problem. I replaced the thermostat and that solved the overheating problem. But the heat still does not work, what could be the problem??

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  3. #2
    NECO Member NfWiseguy's Avatar
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    Re: Heater not working after replacing thermostat

    Does it not work on any setting, on any speed? My controls are finicky. Sometimes you have to go back and forth through the settings to get a particular speed to work and vice-versa.

  4. #3
    NECO Member MattyD879's Avatar
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    Re: Heater not working after replacing thermostat

    If it doesn't blow any air at all, or only works on one of the settings, check the heater blower resistor.

    It's located on the bottom of the blower motor on the passenger side(on the bottom of the dash).
    They rust out a lot of times from a build up of condinsation in the blower motor.

    Heres the how-to. Very easy to check to see if thats the problem.
    fixing heater blower resistor - install photos
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  5. #4
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    Re: Heater not working after replacing thermostat

    All the settings work. It blows air at all speeds and on all settings. Its just not warm air.

  6. #5
    Capital Curmudgeon Lifetime Platinum MemberModerator skater's Avatar
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    Re: Heater not working after replacing thermostat

    You have air in the coolant system, probably. You have to bleed it.
    1999 Cougar, Laser Red, 3.0L V6, MTX (a lot more fun)
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  7. #6
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    Re: Heater not working after replacing thermostat

    Quote Originally Posted by skater View Post
    You have air in the coolant system, probably. You have to bleed it.
    x2

  8. #7
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    Re: Heater not working after replacing thermostat

    What the best way for me to bleed the system.

  9. #8
    Capital Curmudgeon Lifetime Platinum MemberModerator skater's Avatar
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    Re: Heater not working after replacing thermostat

    Fill the system to the full mark with the engine cold.

    Run the engine until the thermostat opens and starts circulating coolant and let it run for a couple minutes. This will move air bubbles to the top.

    After the engine cools off again, add more coolant. It's best not to add cold coolant to a hot engine for obvious reasons (well, it can be done in small amounts to top off the system or what have you).

    You may have to repeat this process a couple times to get all of the air out of the system.

    At least, this is how I've done it. I'm sure there are faster ways.
    1999 Cougar, Laser Red, 3.0L V6, MTX (a lot more fun)
    2006 Ford F-250 Super Duty 6.0L Diesel (tow monster)
    2012 Honda Accord V6, ATX (daily)

  10. #9
    NECO Member RiverRojo's Avatar
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    Re: Heater not working after replacing thermostat

    Cougar systems are self bleeding due to the overflow reservoir dump tube. Make sure you are actually full.

    Then check input and output temps of the heater core. If those are the same I would look into a blend door or blend door actuator.
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