Fan blower only works on high speed....
I have the Itasca detailed below, and lately has developed an issue where the dash fan will only work on the high (noisy!) switch setting. After starting the engine (Chevy workhorse 8.1 engine chassis...
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Incredibly enough, and this may sound counter-intuitive, but I had a bad ground where it connects into the blower motor behave in the same manner. I trouble shot the system all the way from the resistor, to the relay, to the switch with no definitive diagnosis.
The next step was to backprobe from the motor. I removed the panel/vent assembly from the passengers side to get to the motor, and since it happened to be after dark, I noticed arcing as the motor cut in and out, low to high... The motor ground was held on only with a small sheet metal screw mounted to the motor/blower chassis. When I tightened the screw everything worked properly...and at all speeds. After a few off/on cycles, the blower motor stopped working or would work only on high. The screw had so few threads in contact that it had backed itself out and would not tighten. I speculate that it would sometimes work on high only because the higher voltage bridged the gap at the bad ground contact. (thus the arcing)
I removed the blower/motor assembly, filed the paint from the area around where the ground screw mounted, and installed a bolt with a lock washer and nut into the hole. When I reassembled the blower/motor assembly I attached the ground to the bolt with a lock washer and nut. I have not had an issue since.
The next step was to backprobe from the motor. I removed the panel/vent assembly from the passengers side to get to the motor, and since it happened to be after dark, I noticed arcing as the motor cut in and out, low to high... The motor ground was held on only with a small sheet metal screw mounted to the motor/blower chassis. When I tightened the screw everything worked properly...and at all speeds. After a few off/on cycles, the blower motor stopped working or would work only on high. The screw had so few threads in contact that it had backed itself out and would not tighten. I speculate that it would sometimes work on high only because the higher voltage bridged the gap at the bad ground contact. (thus the arcing)
I removed the blower/motor assembly, filed the paint from the area around where the ground screw mounted, and installed a bolt with a lock washer and nut into the hole. When I reassembled the blower/motor assembly I attached the ground to the bolt with a lock washer and nut. I have not had an issue since.
