RV Repair: Duotherm Comfort Control, phone cords, zone 1

Question
My four button duotherm thermostat seems to have lost Zone 2.  It no longer recognizes A/C #2.  Of course Zone 1 controls the front A/C and the furnace...it appears fine, however it now doesn't display the wording " Zone 1" as it did before when I could control both #1 and #2..  Could it be the circuit board on A/C #2?  All of the wires seem to still be intact.

Answer
Pat, There are several things that can cause this. It would be hard for me to say for sure what it is without knowing more. If you check through your paperwork you might have the sheet on this and if so it should tell you how to do a reset to the T-Stat. If this doesn't work then it is probably the upper board but you can test that as well by pulling the inner cover from the ceiling down on the main air and you will see 2 phone cords going into the box. Take and change the order they are in and if the other one works then it is the T-Stat. If not then it is the upper board. I hope this helps. Thanks, Bill