Hi all. I replaced my blower motor, blower motor resistor, and the wire harness. The blower motor resistor and the wires were fried. The air now works, but only at the highest speed. I have a 2012 Ford Fusion SEL with dual temperature control. The temperature changes, just the fan speed does not change when I change it manually. Any suggestions? Could one of the wires not be making contact from my pigtail? I will also add the fan speeds worked before the resistor and wires completely fried.

 

One reason for the resistors and wiring getting overheated is the blower motor is binding internally and requiring more current than the components are rated to carry.
In that case when the motor is removed ,the additional drag ca be felt and usually motor replacement is the solution.
The better way to confirm this is to check the amperage draw with a meter. If the draw exceeds specs, replacement is the cure.

 

Did you ever figure this out? I have the exact same issue

 

When the blower motor is supposed to deliver high speed , because that setting requires the most current, a separate relay is used to provide that power.
All other speeds are available through the resistor.
If the motor bearings are dry and lack lubrication, the motor consumes more current than normal and if any speed below hi speed is selected, the resistor overheats and causes problems. The test is to measure the current consumed OR remove the blower motor and see if it spins freely. If it has more than normal drag, it uses more current and should be replaced.
The most difficult part is having the correct allen wrench to switch out the squirrel cage that spins and produces the air movement.
Not a difficult thing to do if you have the correct tools.