Thanks Virtual, I think you are right about what Comms stands for and I opened up the hatch inside the trailer to the AC last night and traced the 3 wires going back into the Electronic control box and then wires coming out of it that appear to go the furnace. What I have so far found online is this is Dometic's new electronic control box that replaces the old analog one that you and alot of people have in their units that is why I have a different thermostat and only 3 wires so I am thinking my next step is to maybe phone Dometic to see if there is anyway to make this work with a programmable thermostat but I have a feeling they are going to say I would have to revert back to the old controller box and go from there.I will let everyone know what I find out and I hope it doesn't mean it is going to be problematic down the road for people to add their ownn programmable thermostat. I don't understand why RV maunfacturers do this kind of things and call them an upgrade but don't go all the way and make it a fully programmble thermostat.