Hi Gary G.,
There are thermistors that sense the temp. They are covered by a cap with slots in it. The slots allow air flow over the thermistor. There should be two in your coach. One in the bedroom and one in the living area (somewhere). For my coach the difference between the set temp and the actual temp will vary, depending on the outside temp. The hotter or colder the outside temp the more the variance. I compensate by turning the HVAC up or down so the units run longer and maintain the inside temp where I want it. I purchased an inside thermometer (2) and placed one in the bedroom and one in the living area. Now I know what the inside temp is.
The control box where you make temp adjustments and determine if it is heat or A/C that is needed is the brain, but not the sensing unit.
Lastly, I moved the thermistor for the bedroom to just inside the last return air vent. It was located on an outside wall (very poor place for a sensitive thermistor). This also aided in having the bedroom HVAC unit run the appropriate amount of time to maintain the correct temp.
FYI, thermistors are VERY sensitive to temp change. For the bedroom thermistor, I had to wrap it in heat shrink plastic to desensitize it.
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