Indoor unit shows F3, and heating or cooling cycles are unstable; defrost may not work correctly.

Safety first: Disconnect power before opening the outdoor unit.

• Step 1 – Find the coil sensor: Look for a probe clipped to the outdoor coil tubing or fins.
• Step 2 – Check attachment: Ensure the sensor is firmly clipped and making good contact with the coil surface.
• Step 3 – Test resistance: Disconnect and measure resistance. Compare to the specified values. Replace if defective.
• Step 4 – Install replacement: Fit a new condenser coil temperature sensor, clip it securely to the coil, and reconnect to the PCB.