I have a Ducane CMPB075C3A. The inside blower motor does not run, I hear a click when it tries to turn on followed by a hum, the hum continues. I suspect the circuit board is bad but would like to test the motor by running 110v directly to it. Which wires do I connect voltage to? It has 4 wires going to it; white which I am pretty sure is common, red, blue and black. Thanks for any help.

Yes, white would be neutral & you can use any of the other wires since they are just different speeds. When testing be sure to cap or tape the ends of the unsued wires. If the fan doesn't start with a test cord, try giving it a spin by hand. If it then starts, you likely have a bad capacitor.