Unit stops during operation, indoor display shows E4, sometimes after long cooling cycles.

Safety first: Turn OFF power at the breaker before inspecting the outdoor unit.

• Step 1 – Clean outdoor condenser: Remove any covers or guards as per the manual. Clean the condenser fins with a soft brush and low-pressure water. Ensure good airflow around the unit.
• Step 2 – Check outdoor fan operation: Restore power and run the unit. Confirm that the outdoor fan starts whenever the compressor runs. If the fan is not spinning or is slow, shut down the unit to prevent compressor damage.
• Step 3 – Check ambient conditions: In very high outdoor temperatures, E4 can occur if the unit is undersized or airflow is restricted. Improve shading and ventilation around the outdoor unit.
• Step 4 – Inspect for oil stains: Look for oily spots on flare joints or service valves, which may indicate refrigerant leaks.

When to call a technician: If E4 persists after cleaning and confirming fan operation, a certified technician must check refrigerant pressures, locate leaks, and possibly replace the expansion device or sensor.