Heat-A/C control problem
 

Can anyone tell me where to check the circuit going to the main heater/ AC control panel? All the fuses I have been able to find in the cab and under the hood are in tact, but there seems to be no power at all to the controls. I also switched some relays around with things that are working, but no luck. The fan switch "feels" ok, but I have not pulled it out yet to check it. I probably need to find a good repair manual and/or wiring diagram. Any help would be appreciated.