F3 error, the outdoor unit does not start or stops shortly after starting.

Safety: Turn off the outdoor isolator or circuit breaker. Wait several minutes for the capacitors to discharge before touching the outdoor unit.

• Locate sensor: Remove the outdoor unit’s top or side service panel. The ambient sensor is usually a small NTC with two wires, mounted near the air intake grille or on the coil frame.
• Visual inspection: Check if the sensor body is cracked, UV-damaged, or hanging loose. Ensure it is positioned in free air and not touching hot components.
• Check wiring and connector: Follow the sensor cable to the outdoor PCB. Clean any corrosion on the connector and reseat it firmly.
• Measure resistance: With the sensor unplugged, measure resistance and compare to the expected value for the current outdoor temperature. Replace if it indicates an open circuit, a short circuit, or is far out of specification.
• Replace sensor: Install a new outdoor ambient NTC sensor, mount it in the same location, and secure its cable away from fan blades and sharp edges.
• Test operation: Restore power and run the system. Confirm that F3 clears and that the unit responds correctly to outdoor temperature changes.