Redhotnrolli_n
Guest
On the cab fan thing, it can be either one, most of what I've seen tho, is the lo, med, or hi winding in the blower motor is bad. When there are 4 wires on the motor, one is a ground, the other 3 are the speeds. All three carry 12 volts, the switch routes that 12 volts to wire A, B, or C. The same 12 volts also enters the switch thru a "feed" wire. Run a jumper from that feed wire to the speed wires one at a time with switch in the "off" position. You will get lo, med, and hi as this is done. If one speed fails, it's the motor. If no speeds fail, it's the switch. Try this test first. Remember,"No return on electrical parts".