This vehicle does NOT use a heater control valve. Coolant flows to the heater core at all times. Temperature is regulated by the blend air door and blend door actuator. Locate the blend door. Remove the actuator and open the door by hand. If you get heat, the actuator or the control head is bad. FWIW, the actuator is the most likely cause
SOURCE: Mercury grand marquis 1997 temperature control
I'm not sure if yours is identical to mine since yours is second gen and mine is third gen, but with mine (1998 MGM), the heat was stuck on all the time. Full heat would practically cook your feet and you couldn't shut it off.
It was a servo/servo arm that controls the hot/cold mix door. The part was $15. The labor was $700. They had to take the entire dash out of the car to get at the part. Required two more visits due to a missed electrical connection to a daylight sensor and a vacuum issue that made the car stall when put into reverse.
My car had 150K on it at the time. Has 165K on it now. Still runs great and looks great. It's now my wife's auto and I drive a 2006 MGM.
SOURCE: 2000 grand marquis cruise control not working
Have seen this problem before. You need to look under dash at brake pedal and find a blue switch with plunger contacting pedal, disconnect connector and jump with a peice of wire and drive to see if cruise works and if it does replace deactivation switch this should get you going.
SOURCE: need to know where the heater core and heater
The heater core is on the passenger side under the dash within the heater airflow contoller box. If you had Xray vision and could look straight through the glovebox, then you would see it. The heater control vale for the water flow is on the passenger side top of the engine near the firewall. It will have a domed top with a vacuum line to it and it is placed into the heater core supply hose.
Testimonial: "very helpful and quick"
SOURCE: 2003 mercury grand marquis LS
The blend door is stuck in cold position. That usually happens because the blend door actuator has failed.
You will need to test and replace the blend door actuator.
To replace the actuator you will need to take apart the dash and remove completely the instrument panel,d isconnect the connector, remove the four screws, remove the temperature blend door actuator and replace it.
The replacement is not a job for beginners, since you have to take apart the dash to access the actuator.
Regards.
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