I was having a problem with the thermostat reading wrong. Dometic sent a new thermostat and a relay box. The thermostat triggers the relay box which in turn operates the furnace. On my Rushmore, the relay box is accessed inside the main A/C unit, by removing the filter cover. The relay box has several connectors. If one is loose, or a wire in one of the connectors is loose, you could have intermittent control operation. You might want to check for loose wires at the thermostat.