If the RV has reached the desired temperature but the furnace fails to shut off, the thermostat will request more heat from your furnace. This can create rather balmy conditions in your rig. To troubleshoot this RV furnace problem, use a multimeter to check the voltage from the thermostat to the time delay switch. If voltage is present, the thermostat has failed. If there is no voltage, there’s a short somewhere in the system.