Indoor unit displays E4 and the unit stops; may occur during heating mode on heat pump models.

Safety first: Turn off power at the breaker. The compressor and discharge line can be extremely hot; do not touch bare copper lines.

• Clean outdoor unit: Remove debris and clean the condenser fins thoroughly. Ensure good airflow around the unit.
• Check outdoor fan: Restore power briefly and verify the outdoor fan starts and runs at normal speed. If not, disconnect power and inspect the fan motor, capacitor (if used), and wiring harness.
• Check for airflow obstructions: Ensure no covers, plants, or walls are blocking hot air discharge from the outdoor unit.
• If E4 persists: The discharge temperature sensor or compressor may be faulty, or the system may have refrigerant issues. A qualified technician should measure discharge temperature, check refrigerant charge, and replace the discharge sensor if defective.