Question about 1999 Jeep Grand Cherokee

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Where exactly on the heater hoses''

I cant find the heat control valve on 1999 jeep cherokee limited V-8 is it at the end before the firewall at the other end. I disconnected something that sort of resembled it by the master cylinder and it go warm for a minute but went right back to cold. Please help. Still freezing...

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  • Richard Scordino May 11, 2010

    Is temperature gauge reading normally? I can't remember exactly where it is on that engine, but, if you follow either of the heater hoses from the firewall towards the engine, the first thing you will run into is the control valve if you have one. It may have several connections to other hoses, but it will always have a small vacuum hose attached. In general, they don't go bad too often, unless they are leaking.Check to make sure it is operating... remove the vac hose and see if the little arm that operates the valve moves Check if there is vacuum at the small hose (try with ac on and off) this should get you moving in the right direction. If all seems ok, make sure when the control is moved that the interior plenum door is moving (either vacuum or cable operated, under dash)

  • yadayada
    yadayada May 11, 2010

    Wjhy do you think there is a heater control valve? I don't think that is the problem.



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Your control valve is in the dash assembly, passenger side. buried. its not in the engine compartment. im having the same problem with mine...i am thinking its more like the climate control is screwed up.

Posted on Dec 17, 2008

  • glosol Apr 17, 2009

    And to let everyone know...There is no valve on the heater hose to heater core that restricts coolant flow in any way. The heat is controlled by one of the infamously faulty air control flaps allowing more or less air across heater core as needed for reaching the right temps. On climate control units, there is a built in diagnostic code reader. To check codes:

    1. start jeep

    2. press a/c and recirculation buttons at same time

    3. turn drivers temp control rotary knob 1 or 2 clicks clockwise

    4. write down the codes that are shown and run a google search



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1 Answer

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1 Answer

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