Heating/cooling system fan speed

Asked by Dec 21, 2015 at 11:00 AM about the 2007 Mercury Grand Marquis LS Premium

Question type: Maintenance & Repair

On control panel, the fan speed is full 'on' or full 'off'. All other functions work.

7 Answers


Has to do with the resistor that controls the voltage for the different speeds of the blower motor. Replace it.

1 of 1 people found this helpful.

Rowefast: Thank you for your response. I have tried to find the electrical schematic for the system but haven't seen one yet. Now to look up the location for the resistor...I know about where it is, but getting to it is another thing.


Usually it is by the blower motor, follow the wires from the blower motor back to an electrical devise with a plugin. Sometimes easier said than done. In the mean time I will do some checking.

1 of 1 people found this helpful.

Ok I looked up some parts, there is also a HVAC Blower Motor Control Module and the resistor. Either or, or both could be bad, but chances are it would be the resistor.

1 of 1 people found this helpful.
Best Answer Mark helpful

I have to do it the inexpensive way first...the resistor. Thank you for your rapid response. P.S. I have just watched a video for replacing the resistor, it is above my work-grade (I fix computers). I have a locate garage that I have used before (and trust), I'll get them on this soon.


The blower motor control and resistor are the same. It just depends on if its auto or manual a/c controls. Per usual you are spot on Rowefast.


Hey thanks man!

1 of 1 people found this helpful.

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