2008 bighorn 5th wheel electrical issues

[wdk450]

Thank you for for the help. I got the battery the refrigerator is on and staying on but the a/c still won’t come on. Not sure if it has a bad connection or if the whole unit took a crap. Any ways of checking?

Did you ever check the DC fusepanel for lit fuseblown indicator LED's? You might even remove and re-insert every 12 volt fuse, just to ensure they are making good electrical contact in the fuseholders.

The HVAC electrical control is done with the thermostat and the controller board in the metal box on the bottom of the AC, accessible by removing the inside AC trim panel. The AC box sends control signals on to the heater, if needed. Easiest primary testing of this control circuit is to switch the "fan" switch on the thermostat ON. Also try to put the thermostat in "Heat" mode, set the thermostat request to a high number like 90 degrees, and see if the heater fan comes on. The heater is entirely powered by the 12 volt DC system - The air conditioner is controlled by the 12 VDC thermostat, but runs on 110 VAC power.

The thermostat should have +12VDC on each of the incoming wires from the AC control box except the ground wire. The thermostat connects the signal wires to ground to send the switching signals to the AC control box. The ground should be the blue wire, and shorting any other wire to blue should make that function work. Note that the Yellow wire is for the AC compressor, and the AC compressor should not be running without also one of the fan speeds running.