Furnace intermittently shuts down with E11, indicating a return air temperature sensor fault

Safety first: Turn off power before accessing the control or sensor wiring.

Steps:

• Locate return air sensor: Find the Danfoss NTC sensor mounted in the return air duct or blower compartment.
• Inspect mounting: Ensure the sensor is properly inserted into the airstream and not touching hot metal surfaces that could distort readings.
• Check wiring: Follow the sensor cable to the control board. Look for insulation damage or points where the cable may be pinched. Reseat the connector.
• Replace if defective: If the sensor shows open or short circuit when measured with a meter, replace it with the specified Danfoss return air sensor.
• Reset and monitor: Clear the E11 code and observe operation over several cycles to confirm stability.