No power to the thermostat

[6ftunder]

2018 big country, no power to the living area thermostat. At this point I have checked all fuses to include the front storage area, the breakers, the fuse panel next to breakers. I’ve taken the thermostat to the roof plugged in directly to the unit. Replace circuit board and the hard start capacitor ( the reason I did that was the hard start capacitor was burnt , the wsx-7 which is known for that and discontinued. I’ve also taken the thermostat from the front unit and switch them out still nothing. Talked to an a/c guy tested everything coming out of the circuit board and from what he thinks it’s all working fine.

A little backstory, the spring I had a mouse, eat the data line, going from the thermostat to the air conditioner, replace the line. He also ate through the low volt for the air conditioner, and I repaired that. It worked fine when . The next time I came back, a fuse is blown replace the fuse, and this has been going on ever sense.

 

[wdk450]

If you have the thermostat/control box wiring information you can wire in a "dummy" basic thermostat at the control box to start at the smallest circuitry to test AC control operation. On my single Brisk Air II, the older Dometic thermostat is supplied with +12 VDC to the thermostat common buss, and control box functions are switched on by connecting the AC control wires (Cool/compressor, Fan high speed, fan low speed and Heat (sent on through the AC control box to the furnace) to this common +12 VDC buss. Inside the control box relay primary circuits having -12 volts attached to the coils are completed by connecting the thermostat control wires to the +12 volts through the thermostat/switch selection actions.

 

[6ftunder]

Wow what you’re saying is so over my head. I’m sorry, if you’re saying to take the thermostat up to the roof and plug in directly to the control panel I did that. If your saying something else it’s so over my head.
I did have a house a/c friend talk me through to put jumpers on the control board and it all works. Just not the thermostat and can’t figure out going to need it soon for my heater also.

 

[wdk450]

If its not the thermostat or the control board, the only other possibility is the wiring.
Try new wiring just run through the rooms from the thermostat to the control box to prove/disprove this theory. If existing wall wiring is shown to be defective, you can then run the test wiring through the walls.

 

[6ftunder]

Basically I did that by taking the thermostat to the roof top unit and plugging it in directly. There by bypassing the wiring in the walls. The voltage there is 2 are hot with both having 12 volts also. I’m so confused.

 

[Roller4tan]

DC power runs to the ac / furnace control. Thermostat wiring is then run from there to mounted tstat. So if it works at the ac then you have an open in the wiring to the tstat, more than likely a result of your furry intruder.