RV Repair: Duo-Therm Penguin II thermostat, monaco coach, duo therm

Question
I have a 1990 Monaco Coach with duel AC's. They are exactly the same and both are ducted into the celing. The thermostats are remoted to the wall aprox. 10ft.for the front and 6ft for the rear. The rear thermostat is off by about 4 degrees and the front is off by about 22 degrees. Both reading low. I swapped them and the problem stayed the same. I purchased a new thermostat and tried it in both positions,still the same.I did a resistance check on each wire from the control board to the thermostat and the resistance of each of the 11 wires is from .3 to .6 ohms. I also swapped the control boards and that didn't make any differance. I can live with a 4 degree error but in order to stay cool in the front I have to set the thermostat to 60(as low as it will go)to get the temp. in the front of my coach to 82. Is there anyway to ad a resistor or change a resistor to calibrate the thermostat for the position it is in?

Answer
Hi John:

I have been doing a lot of research on this particular problem you are experiencing with your air conditioning system thermostat. You certainly have performed the obvious checks and testing. I may have found something that may help you. Does your thermostat have four buttons on its right side? If so, various models have an option for placing a remote sensor across the room, etc. in order to better maintain a even temperature. If your RV thermostat is wired this way, the thermostat may be sensing a warmer area within the RV. I know often times it is hard to obtain the model and serial number of your equipment, however there are so many variations of HVAC equipment its necessary to be sure we have the proper service documents. When you have a chance to determine wether or not your thermostat has a remote sensor, I will need for you to supply me with the model and serial number of the unit and thermostat. Quite often, the origional books suplied with your RV, may contain this information.

I will be awaiting a reply for you. If necessary, we will continue to persue an answer.

If I can be of further help, please contact me.

Regards, Larry