PROBLEM:
My HVAC blower, behind the glove box would not run.
There was voltage at the harness connector, for low and medium, but not high setting.
When I replace the motor, there was no change.
When I measure resistance from the ground wire on the harness connector to the chassis, there was no resistance.
When I replace the motor control resistor, there was no change.
When I connected the motor directly to the battery, it ran.
When I plugged the motor back into the harness, it would not run on any setting.
When I connected one spade on the motor connector to voltage and the other to ground, it ran.


RESOLUTION:
Replaced the blower motor switch.
The old switch had dielectric grease inside that has was old and crusty on the contacts. There was enough contact to allow voltage, but not enough to carry the current needed to run the motor. In addition, the main contact was overheating and was melting the case.

part number: unknown
Purchase source:
I hope this helps.