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Lincoln Forum: Heat blows cold when stopped at a light warm with acceleration.
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  1. #1
    Join Date
    Jul 2016
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    Heat blows cold when stopped at a light warm with acceleration.

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    Just lately I noticed cold air blowing when i come to a stop at a light. It also happened in park. When I have higher rpm I get warm air. Low rpms get cold air. I'm going to get an OBD code.

  2. #2
    Join Date
    Jan 2010
    Location
    South Bend, IN
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    71
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    470
    I suspect a small vacuum leak. Vacuum operates the doors in the HVAC system. FWIW, vacuum leaks are a bi*ch to find.
    '11 MKT 3.5 EcoBoost AWD; '14 Jeep Cherokee Ltd. V6 AWD
    '00 Regal 29' Commodore twin 4.3L


  3. #3
    Join Date
    Mar 2017
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    3
    Did you ever find out what the problem was? I have the same problem and its been into the shop 3 times for it and they can never find the problem.

  4. #4
    Town's Avatar
    Town is offline Senior Member My Lincoln(s): 2017 Lincoln Continental Reserve 2.7 AWD
    Join Date
    Jan 2013
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    Ottawa Ontario Canada
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    Quote Originally Posted by Turbo Lewis View Post
    Did you ever find out what the problem was? I have the same problem and its been into the shop 3 times for it and they can never find the problem.
    I am not familiar with the MKT, but in my experience you can check the coolant circulation and the coolant level as possible sources of your problem - unlikely a shop would miss those though. Find the coolant hoses going to the heater core. With a warm engine idling in park see how warm the hoses are. They should be very hot to the touch, but if not does running the engine at higher rpm increase hose temperature. One hose feeds into the heater from the top of the cyl heads cooling passage while the other returns coolant to the coolant pump. If they are much the same (hot) temp then the heater core is ok and coolant level is ok. If the coolant out of the heater core is cool while the coolant in is very hot then you have a restriction in the heater core such as an air lock or debris. If the hose carrying coolant into the heater core is not very hot then you have a low coolant level or air lock in the top of the head coolant passage. These two factors can often occur when filling the system or after a coolant leak due to the engine being higher or even with the point for adding coolant (low profile front end design). Can you check the coolant level in the engine through a bottle included in the cooling system (rather than an overflow bottle), perhaps you have a rad cap.

    I would have thought the HVAC system would use electric actuators (rather than vacuum actuators but I don't know) to control the air distribution doors. If an actuator fails it would cause a code to be generated in the control module but it is not an OBD2 code. There should be a self test for the HVAC system that you could run yourself. The test if applicable would be documented in the Lincoln service manual but it does not appear usually in the owner's manual. Did the shop do a self test? If you have automatic heater temperature control then an actuator is moved to open or close the door to allow heated or cooled air into the cabin. The door has a default position that the door moves to if the actuator fails but I have not heard of the actuator not operating at idle while working at higher rpm.

    Good luck.

  5. #5
    Town's Avatar
    Town is offline Senior Member My Lincoln(s): 2017 Lincoln Continental Reserve 2.7 AWD
    Join Date
    Jan 2013
    Location
    Ottawa Ontario Canada
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    72
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    2,676
    It appears that most Lincolns use much the same EATC self test procedure. You could try the self test for my 2007 model Town Car here in post #10:

    http://lincolnforums.com/forums/thre...EATC-Self-test

    If your system is vacuum controlled then this will not likely work.

    Good luck.

  6. #6
    Join Date
    Mar 2017
    Posts
    3
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    Thank you I will try it.

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