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    #1

    HVAC stuck on vent.

    The problem I am having with my 1985 Mercury Grand Marquis with the manual HVAC controls is that the HVAC is stuck on vent.

    I've already tried flooring it while the HVAC is set on defroster and it failed to move to defrost mode, and I've watched all three vacuum solenoids under the dash (two just above the floor vent and one in the passenger side foot well) function as they should, but no air will come out of the floor or the defrost vents. I closed all the dash vents to see if I could force some air through, but no such luck. The heat and cold switches over as it should and the fan blows strong,, but the air doesn't go anywhere but to vent.

    What else do I have to check? Has anyone else dealt with this before?
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    #2
    Originally posted by wildmanjoe View Post
    The problem I am having with my 1985 Mercury Grand Marquis with the manual HVAC controls is that the HVAC is stuck on vent.

    I've already tried flooring it while the HVAC is set on defroster and it failed to move to defrost mode, and I've watched all three vacuum solenoids under the dash (two just above the floor vent and one in the passenger side foot well) function as they should, but no air will come out of the floor or the defrost vents. I closed all the dash vents to see if I could force some air through, but no such luck. The heat and cold switches over as it should and the fan blows strong,, but the air doesn't go anywhere but to vent.

    What else do I have to check? Has anyone else dealt with this before?
    Mode selector door is broken most likely. Gotta pull it apart and replace/repair it

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      #3
      Originally posted by 86VickyLX View Post
      Mode selector door is broken most likely. Gotta pull it apart and replace/repair it
      Where's that located?

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        #4
        pull the entire dash back... it's inside that whole mess of ducting that holds the heater core, all the vent selector doors (2 or 3... same number as vacuum actuators), the blend door (hot/cold), and the fresh/recirculate door.

        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

        Originally posted by gadget73
        ... and it should all work like magic and unicorns and stuff.

        Originally posted by dmccaig
        Overhead, some poor bastards are flying in airplanes.

        Comment

          #5
          yep, in the BS in the center. The hinge likely snapped. Its just a plastic hinge that breaks over time. I rebuilt mine using small steel hinges from the hardware store.
          86 Lincoln Town Car (Galactica).
          5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

          91 Lincoln Mark VII LSC grandpa spec white and cranberry

          1984 Lincoln Continental TurboDiesel - rolls coal

          Originally posted by phayzer5
          I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

          Comment

            #6
            Originally posted by wildmanjoe View Post
            Where's that located?
            It's what all those little vacuum things are attached to...

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