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Thread: HVAC switches mode by self when in recirculation only

  1. #1
    Hybrid booster
    Join Date
    Nov 2008
    South West Washington State

    HVAC switches mode by self when in recirculation only

    Noticed today that the 87 Shelby Z climate control will switch from panel to floor on it's own consistent with throttle application, but only when in recirculation mode. More gas and the more it switches to floor. Switch it back to just cold and it goes back to what ever mode I have it set at. I am guessing it is either the actuator for the recirculation door or the control itself. But wondered if anyone else has had this experience.

  2. #2
    turbo addict
    Join Date
    Dec 2005
    Lincoln, Nebraska

    Re: HVAC switches mode by self when in recirculation only

    Check valve near the brake booster is not working properly, or there is a small vacuum leak in the system after the check valve. Having it on recirculation puts additional strain on the hvac vacuum system and it loses enough vacuum to change mode, but not quite enough to change from recirculation.
    “If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford

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