Blend door or heater core problem?

Discussion in 'KJ General Discussion' started by rigid, Nov 7, 2019.

  1. rigid

    rigid Full Access Member

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    Not sure what the next step should be. All 4 motor speeds work. Vent selector changes as it should. Heater hoses are hot. Air is slightly warm but not hot at all. Coolant is full. Ac does not work so it does not change when switched from hot to cold. I can try to flush the heater core before I would attempt to change it. How can I tell if the blend door is working ?

    Thank you
     
  2. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    What year are we talking about? You should be able to hear the motor working when you move from hot to cold or vice versa. Get you ear up to the dash and see if you can hear a buzz.
     
  3. rigid

    rigid Full Access Member

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    Sorry about that. It is 2003 Should I be able to see the flap door or linkage behind the glove box move?

    Thanks
     
  4. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Doubtful you'll see anything but wouldn't hurt to watch while you're listening. My 02 made a distinct buzz when the motor worked. Mine failed slowly. The door defaults to cold when the engine is shut off. The motor worked fine in that direction but would stick going from cold to warm. finally it just stopped completely. It's possible that the door is stuck. In that case the motor will probably still buzz.
     
  5. rigid

    rigid Full Access Member

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    I flushed the heater core and water was clear from the start. No change in heat. I do not hear any noise where I rotate the switch. Now to top it off this has to be a daily driver for a while. Hit a deer with primary vehicle last night. 4* this morning. Don't have 10 hours to take the dash out right now. I have heard about cutting a hole in the box and moving the door by hand. Do you know exactly where they do this? Also i was a year off, this one is a 2002

    Thanks for your help
     
  6. Billwill

    Billwill Full Access Member

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    Use the Search function Top Right on main page.
    Typing Blend Door got me lots of results!
     
  7. Jeff Ferguson

    Jeff Ferguson New Member

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    My '04 Liberty had following symptom:
    Barely preceptible heat when dial in red zone (min or max)

    Other factors:
    A/C works fine
    Blower motor works all 4 speeds
    Defrost to Floor vents all work fine
    Temp gauge in middle, rock solid
    Both heather hoses to and from heater core are extremely hot.

    What I did:
    Inspected for loose vacuum lines, loose electrical plug-ins (found nothing)
    Flushed heater core only by filling with Prestone flush (30 minutes)
    Flushed and backed flushed with garden hose spray nozzle both inlet and outlet
    What came out was not impressive, transparent pink/rust in color for 15 seconds than ran clear for next 5 minutes

    Somehow, someway it fixed the problem, could cook marshmallows in the cabin now. What gives? Was sure it was blend door actuator or dial controller.
    Grateful for this forum as i would not have given this idea the time of day but am thrilled it works!

    Jeff
     
    Last edited: Nov 15, 2019
  8. rigid

    rigid Full Access Member

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    Don't have time until weekend take the dash apart and also wanted to try to find out what the problem is for sure. I heard no noise when using the switch but they tell me around the hose that I don't hear anyway! Cut a hole to see if a problem was obvious or I could manually move the door for now to get heat.
    When I rotated the switch the door does not move. There are no obvious broken pieces. I am afraid if I try to force it to move something will break. Any quick suggestions for now? Will I have to take the whole dash out to change the actuator? Is it possible to tell by the attached photos if the door is in the heat position? I can feel that it is shut all the way.
    Thank you
     

    Attached Files:

  9. Billwill

    Billwill Full Access Member

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    The motor that moves the doors is a Stepper motor ie. it receives pulses from the controller to take one step at a time in either direction and then stop solidly. If you remove the motor and rotate the shaft by hand you can feel this stepping action but the shaft must not be seized solid!

    These motors can seize up but it could be the control panel ie. the switch.

    Download the 2003 Jeep KJ Service Manual here and go to page 8W-42-1 onwards …...shows lots of fuses and connectors that are relevant and also the grounding point nearby which may be dirty or loose!

    www.colorado4wheel.com/manuals/Jeep/KJ/
     
  10. rigid

    rigid Full Access Member

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    Thanks Bill. I will look through that section and see if I can find something.
    If both hoses to the heater core are hot wouldn't that somewhat eliminate that part?

    I know the door is not moving when the temp dial is turned and from what I found in a video it looks like mine is in the hot position.

    If the temp control dial was bad and it is in the hot position there still should be heat right ?

    I hate to throw 150$ and a whole day at this thing until I am somewhat sure where the problem is.

    engine temp reads in the middle and heat gets no better at hwy speed. all other selectors work fine . Also to remove the motor and move by hand don't I have to take the dash Out?

    Thanks
     
    Last edited: Nov 15, 2019
  11. rigid

    rigid Full Access Member

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    Just used CLR type mixture for 20 minutes and flushed again. Nothing but clear water. If it was plugged shouldn't I get a least some dirty water? Again both hoses are hot at operating temp. Ac condenser leaks so air does not work anyway. The blend door is closed off to the passenger side of the duct housing if looking through the hole I cut. Not sure if the heat side or not. The door does not attempt to move nor does the temp change at all when the switch is moved.
    All fuses are good. Is it likely that the switch is bad and is there a way to test it?

    Thank you
     
  12. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    I can't tell for sure but my gut tells me the door is closed in the cold direction. Meaning you should have very little heat. Can you get something hook shaped (maybe a pick) and GENTLY try to move the flap while cycling the switch? I really have no idea how you'd check the switch unless you can find the connector (which is buried in the dash with the motor).
     
  13. Aceofspades

    Aceofspades Full Access Member

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    The motor I remember accessing by cutting a hole behind radio or glove box. I still had a f all of a time getting the screws out.
    I’ve had a new radiator , t stat , coolant and heater core. My heat comes on slow, and only gets hot after a while of driving. My 03 makes you sweat and chaps your lips.
    I wonder if mine opens and closes but not all the way as I can move between hot and cold.