The Room Temperature Sensor is necessary for all Harman pellet stoves and inserts to utilize automatic temperature control, such as the "Room Temp" or "Automatic" modes on older units. If the controller doesn't detect this required probe, usually due to damage or being unplugged, it triggers a 4-BLINK error code at startup. Although the stove can still run in a manual "Stove Temp" or "Constant Burn" setting without the probe, you lose the ability to automatically regulate the room's temperature. When properly connected and placed, this sensor allows your unit to maintain the set temperature with precision, generally within ±1 ∘ F. An optional 14-foot extension wire (Part # 3-20-674101) is available for optimal probe placement.