Duo Therm Comfort Control is dead

[RV6A]

Help,

2009 Montana with single air and furnace. We have only run the furnace one night many years ago and the AC has never been on. We have always heated with a stand alone unit that is vented outside and has no fan to run the batteries down. Works great as it is 40,000 BTU.

The problem is I tried to start the furnace today as I get ready for the upcoming trip and it's 33F in and out of the trailer. There is also 12" of snow covering everything.

The Duo-Therm 5 button Comfort Control has a dead screen. No heat, no AC, no nothing, just a dead screen.

It seems that a tele cable is used between the thermostat and the AC unit. Another tele cable then heads from the AC to the furnace.

The AC needs 12 volts for some reason and as far as I can tell there is not any 12V power going to the AC. I checked all the fuses in the 12V fuse block and they all Ohm good.

Any suggestions? I'm thinking that a mouse may be involved.

Can the furnace be controlled by a simple mercury T-stat?

This is the first real problem we have had with our Montana.