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Thread: Should the compressor run when heater is on?

  1. #1
    Registered Member ScottH's Avatar
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    Question Should the compressor run when heater is on?

    Recently bought a 55 210 wagon that had an aftermarket ac system installed at some point. The controls work off a stock looking heater controller. I have no idea of the manufacturer.

    When I turn on the heater it only blows slightly warm. However I noticed that as soon as I turn on the blower, the ac compressor kicks on as well.

    Does anyone know if the compressor should come on with just the heater? I did verify that the heater control selector when pushed down is working the heater control valve (cable controlled only, as far as I can tell).

    Any info would be appreciated.

    Thanks
    Scott

  2. #2
    Registered Member BamaNomad's Avatar
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    I can't say what the aftermarket manufacturers do, but with newer vehicles, the compressor is turned on with the heater/defroster, with the primary reason being to 'dry' the air and help to faster defrost the windshield. Late model cars have a button/switch so the compressor can be turned off if the user desires, again I'm not sure that the aftermarket systems (VA or ?) have such a function.

  3. #3
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    I thought the compressor ran on cars the past 40 or so years when the defroster was on. For aftermarket stuff who knows.

  4. #4
    Registered Member ScottH's Avatar
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    thanks guys 4 the replies. I have to do more investigation into it, try to figure out maker, age, etc.. I believe its an older system, not many electronics as far as I can tell. The defrost is also controlled by a cable, and it was not on when I tried the heat. I will try to post some pics of some of the components in hopes it might shed more light on this question.

    Thanks again.

  5. #5
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    I believe the A/C compressor is supposed to run on Defrost for no other reason than to allow the compressor to cycle occasionally through the winter so it doesn't seize. It should not run with just heat.

  6. #6
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    An older cable system is not going to intentionally turn on the compressor when the controls are set for heat.

    The servo control Vintage Air systems might do that on defrost, but they won't mix hot air and refrigerated air through the a/c vents like an OEM system will.

  7. #7
    Registered Member chevynut's Avatar
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    First thing I'd do is try to identify the manufacturer of the system (there aren't that many) and give them a call. One system may not be set up to work exactly like another.

    Vintage Air seems to blend hot and cold air at least when on defrost mode. The compressor turns on and the temperature lever controls the temperature. In A/C it's not clear whether it blends cold and hot air or just modulates the compressor to get the desired cold temperature. This is from the instruction manual.....

    Blower Speed - This lever/knob controls blower speed, from OFF to HI.
    Mode Control - This lever/knob controls the mode positions, from DASH to FLOOR to DEFROST, with a blend in between.
    Temperature Control - This lever/knob controls the temperature, from HOT to COLD.


    A/C Operation

    Blower Speed - Adjust to desired speed.
    Mode Control - Adjust to desired mode position (DASH position recommended).
    Temperature Control - For A/C operation, adjust to coldest position to engage compressor (Adjust between HOT and COLD to reach desired temperature).

    Heat Operation

    Blower Speed - This lever/knob controls blower speed, from OFF to HI.
    Mode Control - This lever/knob controls the mode positions, from DASH to FLOOR to DEFROST, with a blend in between.
    Temperature Control - This lever/knob controls the temperature, from HOT to COLD.

    Defrost/De-fog Operation

    Blower Speed - Adjust to desired speed.
    Temperature Control - Adjust to desired temperature.
    Mode Control - Adjust to DEFROST position for maximum defrost, or between FLOOR and DEFROST positions for a bi-level blend (Compressor is automatically engaged).
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  8. #8
    Registered Member chevynut's Avatar
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    One thing I noticed when I was modifying my controls is that there's a difference between Vintage Air 55-56 kits built before January 2016 and those built after. After that date they tie both of the temperature levers together to operate as one temperature control. Same thing happened on '57 kits made August 2017 and later.

    It wouldn't be hard to identify the manufacturer of the unit.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  9. #9
    Registered Member ScottH's Avatar
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    Thanks for all the great info. I was able to find out it's a Vintage Air system. From there I downloaded their install manual. Found out that when the heat lever is pushed down for heat there is a micro switch that turns off the compressor. Turns out that the switch wasn't aligned up correctly with the cable. After a little adjustment it is now working properly. BTW u guys were right about the defroster. There is another micro switch which turns on the compressor when the defroster cable is pushed down.

    Thanks again for every ones input.

  10. #10
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    The compressor runs with the defroster on most all vehicles to dehumidify the air which clears the foggy windshield better.
    Tony

    1955 Bel Air Sport Coupe

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