Haier Air Conditioner Error Code F4

The F4 error code on a Haier air conditioner indicates overheat protection has been triggered due to the compressor discharge temperature exceeding 110 degrees Celsius. The discharge temperature sensor is mounted at the compressor outlet on the outdoor unit and monitors the temperature of refrigerant vapor as it exits the compressor. When this temperature crosses the 110°C threshold, the control board activates protective shutdown to prevent compressor damage. The fault is signaled by LED1 flashing 8 times in sequence.

High discharge temperatures are typically caused by conditions that reduce heat transfer efficiency or force the compressor to work harder than designed. Common culprits include low refrigerant charge, which causes the compressor to handle a lower density vapor load and generate excessive heat, as well as blocked or dirty condenser coils that prevent adequate heat rejection. Restricted airflow across the outdoor unit, a failing condenser fan motor, or a defective discharge temperature sensor itself can also produce this fault.

Diagnosis begins at the exhaust temperature sensor on the outdoor unit compressor. Technicians should verify sensor resistance matches the expected values for the measured ambient temperature, check for refrigerant charge using manifold gauges, inspect condenser coil condition, and confirm the condenser fan is operating at correct speed. If the sensor reads an open or short circuit, it will likely report an out-of-range temperature and trigger F4 even when actual discharge temperatures are within normal limits.