F4 error and the compressor may not start or may shut down quickly.

Safety first: Isolate power before opening the outdoor unit.

Steps:

• Locate ambient sensor: Usually mounted near the outdoor air intake grille, often in a small plastic housing.
• Inspect sensor and cable: Check for physical damage, corrosion, or disconnection.
• Reposition sensor: Ensure the sensor is in free air, not touching hot pipes or in direct sunlight if not designed for that location.

Resolution: Replace the outdoor ambient sensor if faulty. If the error remains, the outdoor PCB may be defective.