Heater fan stuck on high speed

10

Asked by Sep 27, 2015 at 07:06 PM about the 2004 Mercury Grand Marquis

Question type: Maintenance & Repair

Can not change the blower speed from high ---- it will even blow when the key is in the acc prosition

5 Answers

26,065

sounds like the switch is bad...anyone else out there want to add anything>?

2 of 2 people found this helpful.
10

Should it not cut off the power when the key is in the acc position ?

1 of 1 people found this helpful.
10

Is there a relay or temp-speed secencer that may be stuck ?

72,145

There is a resistor that controls the blower motor speeds. When you turn your switch low, medium, high, the resistor regulates the amount of voltage to the blower motor to acquire the desired speeds. In the accessory position the blower motor should be off. When mine went bad the blower motor kept on running on high, even with the key out of the ignitionl

4 of 4 people found this helpful.
68,445

If you have automatic climate control it's going to be the control module in the engine compartment on the firewall. When they fail you either get constant high speed or no blower motor at all. HTH. -Jim

7 of 7 people found this helpful.

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