Originally Posted by Radams
There is no power going from the switch to the fan so it will not turn on at all
The switch is not supposed to supply power to the motor. The switch is installed in the ground side of the motor circuit and is intended to change the resistance of the ground (low side) circuit (via the blower resistor) to change the current flow through the motor and hence its speed.
Locate the blower motor connector. One lead should be battery voltage whenever the blower should be operating. The other lead should measure anywhere from zero when the switch is in HIGH to several volts when in lower speed settings.
If you have battery voltage on one lead but zero volts in all switch settings on the other, the blower motor is bad.
If neither lead has power when it should, check the blower motor relay located in Aux relay box #4.