Mercury Q&A

Ask Your Question

1999 Mercury Grand Marquis Question: my heat works good then it turns cold then back to heat what couls it be?

 

Question

Otto25, East Weymouth, MA, October 23, 2012, 09:20
 Rookie

could it be the actuator blend door motor

4 Answers
Flag This
  • Answer #1

    October 23, 2012, 11:25
     Master

    fords are bad for the heater box door breaking

    Reply
    Flag This
  • Answer #2

    Greg's Orange Auto (13991 Answers) , Orange, CA - (714) 361-9386
    globalhelper October 23, 2012, 13:29
     Master

    could be a blend door but goodguy is correct about the fords and the doors breaking

    Reply
    Flag This
  • Answer #3

    October 23, 2012, 18:08
    Profile_thumbnail
     Master

    REPLACE THERMOSTAT AND BE SURE IT IS "FULL" OF COOLANT!

    Reply
    Flag This
  • Medium-star Best Answer
    October 24, 2012, 16:35
     Journeyman

    I do agree with the other posts but make sure you also check the vacuum supply to your hot water control valve, if the vacuum line has a leak in it the valve will open and close as you accelerate and decelerate causing the heat to come and go. This leak will also cause your A/C to come and go with load differentials.

    Reply
    Flag This