F2 error, indoor unit may blow room-temperature air, system cycles frequently

Safety first: Turn OFF power to the indoor unit before removing the front panel or filter grille.

• Step 1 – Locate room sensor: On many Day & Night ducted systems, the room sensor is integrated into the thermostat. On ducted fan coils with onboard controls, a small thermistor is located near the return air path.
• Step 2 – Inspect placement: Ensure the sensor is in the return air stream, not touching metal surfaces or the evaporator coil, which can skew readings.
• Step 3 – Check wiring: Verify the sensor plug is firmly connected to the indoor PCB and wires are not damaged.
• Step 4 – Replace sensor if needed: If the sensor is visibly damaged or reads open/short on a meter, replace it with the correct Day & Night part.
• Step 5 – Recalibrate (if applicable): Some controls allow temperature offset adjustment; verify settings after sensor replacement.