On my rig, the high setting has been going in and out. It works on low, med, extra medium, but not high, if I put it on high its like it switches back to low. I am talking the blower speed not temp. I checked the wire connections and all seems good. Would this be a switch problem (hvac controlls) or a blower motor problem?

Thoughts?

Thanks!

 

Might be bad resistor board, its located under the motor, that controls the motor speed.

 

On high it should bypass the resistor board and go directly to the motor. Since the motor works on lower speeds but not on high it will be good. These motors work or don't work the voltage going in determines the speed, the higher the voltage the more efficient the motor will be.