Odd problem with a/c thermostat

My 2012 Tiffin Open Road has a thermostat problem that I have traced to the remote sensor.....maybe. The front A/C has a remote sensor about in the center of the coach on the drop ceiling. I noted that the temp was always reading in the high 80' or low 90's even when it was closer to 78-79 by thermometer. I removed the thermostat from the wall and the temperature began to read correctly while only about three inches from the wall and hanging. When I mount it back and stuff the wires in behind the thermostat, the temp goes up immediately apparently reading the temperature inside the adjacent wall. I noted that inside the wall it felt much warmer, but I can't see why just mounting the thermostat should change the reading if it is getting the temp from the remote sensor. I noted that when the sensor wires are disconnected there is nothing at all on the LCD display. Any theories?

Don Smith