Thermostat not recognizing Zone 2

[Montana 2012]

In my 2012 Montana 5th wheel I have a Dometic Dual Control thermostat. All of a sudden Zone 2 doesn’t show up in thermostat controls. Zone 1 continues to work fine. I’ve checked the breaker switch, the phone line connection into the thermostat, the switch settings in side the AC unit. Nothing. Today I bought a new Dometic thermostat and it made no difference, reading out the same as the original one. Tomorrow, after I return the new thermostat and get my leg back, any suggestions on what else to check??

[rohrmann]

We had an issue with the Zone 2 A/C (bedroom) not working. After much investigating, discovered the circuit board in the metal box above the filter had severe corrosion on the board as well as the connections where the comm cable was connected. I bought a new box, https://www.campingworld.com/ccc-ii-...E&gclsrc=aw.ds swapped the bad board with the new one and were back in business. This problem with ours was in 2014. This photo shows the corrosion.