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  1. #1
    Join Date
    Mar 2017
    Posts
    5
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    Heat comes and goes

    I have tried to figure this out for a couple years. When I start the car and begin to drive in the cold weather, the heat comes on after a few miles and works fine. After about ten miles it will start to blow cold air. I can turn the heat up, change the mode settings, etc... and nothing changes it from blowing cold. After another 10 miles or so it will blow heat again and be fine, usually for the rest of the trip. Anyone had any experience with this? I had the usual heater control head light issues, so I bought a new heater control head to get the lights working and I hoped maybe it would also solve this issue. It didn't. It is not low on coolant. I had code P0128 last year and put in a new thermostat to fix that code and it did nothing for the intermittent heat issue. It did it before the new thermostat and after. I'm at my wits end. Anyone have any ideas or better still have the same problem and found the fix?
    2006 Chrysler 300C SRT8
    1978 Dodge Ramcharger
    1973 Dodge Dart Sport 408 stroker
    1970 Plymouth Duster



  2. #2
    Join Date
    Sep 2016
    Location
    Markham, Ontario
    Posts
    70
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    When this happens again, take it on a open road and nail it. If your heat comes back on, you have a air pocket interfering with the flow of coolant. You have to run it and bleed out the system properly using either the allan head bolt on the thermostat housing with the rad cap off, or by the thermostat housing itself by backing off the bolts to it.

    Have you ever used any of that stop leak stuff in your coolant system at any point? That stuff is by far the worst thing to throw into a coolant system. It would need to be properly flushed out. It's like pouring mud in there....
    Last edited by ttype; 10-16-2018 at 08:27 AM.
    2006 Chrysler 300C (heritage edition)

  3. #3
    Join Date
    Mar 2017
    Posts
    5
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    I would never use stop leak in any fluid in my car. I would challenge anyone to get that bleeder plug free. It anodizes itself in place and will not come out. The allan head will strip out. I even tried gentle heat. I bled it through the coolant temp switch. It is not an air pocket issue though. I did run a recalibration of the HVAC actuators to see if that would do anything and twice the recirc door calibration failed. You would think if the recirc door was stuck open or closed it would not make the heat come and go. It should be cooler or hotter at all times. Regardless, the motor calls for .7 to replace so it's easily accessible. I'll pull the motor and see if the door moves freely. If so I'll throw a new actuator motor at it.

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