66 GMC Heater control/switch not working
 

I have a three slider heater control/switch in my 66 GMC that is not working. The middle lever is an air/fan "Off-Lo-Med-Hi" switch. The left lever is DEFROST, and the right lever is HEAT. I can test that the switch is getting power to it via a 4-wire connector that plugs directly into the back of the switch. Power comes from a 10 Amp fuse on the Fuse Panel labeled HEATER / B.U. LPS. Fuse is good, and power is going through it. Any suggestions?

On a separate issue, the Heater Control Bulb was not working either. Found out that the 3A fuse on the Fuse Panel labeled PANEL LPS, which the heater lamp wire was plugged into, had no power. Moved the heater lamp power wire/connector on the fuse panel to another 3A fuse labeled RADIO / BRAKE LP, This fuse had power when the ignition switch is turned on. After making this wiring switch, my heater control lamp worked. Question: Any ideas why there is no power on the PANEL LPS fuse/circuit. Where does power come from for that panel fuse. Can't tell from looking at the front of the fuse panel.

Re: 66 GMC Heater control/switch not working
 

Are you saying the fan isn't working? Could it just be a bad fan motor?

Re: 66 GMC Heater control/switch not working
 

Yes, it could be the fan. Where is the fan and how do you get to it?

Re: 66 GMC Heater control/switch not working
 

im about 200 miles from Cecilia right now but in this pic from my build thread you can see a metal contraption above the passenger footwell. I believe that's the motor housing.

http://windypix.com/?di=OXOG.jpg

Re: 66 GMC Heater control/switch not working
 

With the connector connected to the switch and the switch on high, you should have voltage going to the switch, leaving the switch, then going the the firewall connector, and all the way to the motor connector. Also make sure your ground is good. There should be no voltage on the motor ground wire. If there is the there is no ground.

The power come from the same source as the dash lights. Check your wiring diagram for wire color, they should be the same.

Re: 66 GMC Heater control/switch not working
 

All of my lighting problems were grounds.

Is there a pinout for the heater slider switch? Is there an actual ground wire. Or does the metal fan housing (if properly grounded) serve as the ground connection?

Re: 66 GMC Heater control/switch not working
 

I do not have the wiring manual for your truck so I would not know. On my 64 it is grounded to the body of the motor. If your is the same then the motor to the blower housing and to the cab should have a good ground.