The on-board room temperature sensor is connected to the 2 position terminal block mounted on the room temperature sensor panel. It senses the current room temperature and sends this information to the processor control board.
This sensor is a small, round thermistor with a lead wire soldered to each side of it. The thermistor is a very accurate device and will very seldom fail. Generally, if there is a problem with the accuracy of the room temperature reading, it is due to inadequate air flow to the right side of the heater due to placement of the heater. In these instances, a remote room temperature sensor is recommended.
If this is not the case, there may be a short or open on the room temperature sensor. The two lead wires connect into the 2-position terminal block inside the right side panel. Due to the very small lead wires on the sensor, the leads are installed to extend through both setscrews of each position on the terminal block. Make sure the room temperature sensor is not shorted to ground and that it is positioned away from all metal parts. To test the sensor read resistance across the lead wires and compare the reading to the Temperature Sensor Resistance Chart.