Question about 2000 Mercury Grand Marquis

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No heat in my 98 Grand Marquis

I have flushed the system and replaced the thermostat (twice to be sure) and blew water through the heater core. I still have no heat. I am wondering if the temperature control unit is not sending the signal to direct the airflow through the heater core. Does anyone have any ideas?

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  • slackkeymike Jan 22, 2009

    I will add that the first time I replaced the thermostat, 2 yrs ago, it started working again! Then some time later it stopped. That made me think trash in the heater core. I did replace the thermostat once again, but no improvement. You asked for a clarification, but I am not sure what you are looking for. Is there a way I can test the TCU and HCV? Surely there is someplace where the mechanism reroutes the air through the heater core. Diagrams anyplace?



    Mike

  • Richard Delahant May 11, 2010

    It could be the temperature control unit, without checking it it;s only a guess. Could also be the heater control valve.

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Are you shure that you dont have trapped air in the heater core? get a big funnel that will fit tightly in the radiator filler and fill with coolant and run the car to normal operating temp and watch for the level to drop or bubbles to evacuate into the funnel. on really stubborn air locks i have had to squeeze the hoses to pump water through the heater core.





































































Posted on Feb 11, 2009

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