heat problems

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Thread: heat problems

  1. #1

    Join Date
    Jan 2014
    London Canada

    heat problems

    Hi guys. I pulled my 1987 Supra out of storage. This is a Canadian model so the heat/ac numbers are celcius. My heat and a/c work fine except that I don't get heat until the temp is set at 30 degrees (that's about 90 degrees farenheit). Last fall it pumped heat out when the temp was set at 20 degrees celcius (72 farenheit).
    Any thoughts? I'm hoping for a simple solution...
    Thanks doug

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  3. #2
    YotaMD.com author
    Join Date
    Sep 2007
    My first thought is to check the HVAC heater mixing valve in the engine bay, near the firewall. If that goes bad you'll get faulty mixing for heat/cool. You can override it easily by switching around vacuum hoses. I think you can play around with it and watch it move around while changing the thermostat in cabin.

    If I recall correctly when it fails, it normally loses heat.

  4. #3
    THE LAST NA SupraCooled's Avatar
    Join Date
    Mar 2009
    Bohemian Grove, CALIF
    The heater valve is sticking......it wont be long until you have no heat at all..

    3 options

    Bypass the switch, hook up vacuum directly,
    or undo the hook on plastic and open it manually,
    or zip tie it open

    Replace heater valve?

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  6. #4
    90T 3p141592654's Avatar
    Join Date
    Sep 2005
    Thousand Oaks CA
    If the valve is sticking you will get no heat period. This is a control issue with the damper. I would start by making sure the temp sensors are working.

    If the damper has not being pulled out and the resistor traces cleaned, then that is also a very likely problem. The usual symptom is hunting of the damper, but if it gets really bad it can stop working all together. There is a post on here or maybe its SM on how to clean it.


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