Indoor unit displays H1; unit may run in a special mode with reduced airflow; often appears in heating mode.

Safety: H1 often indicates a normal defrost cycle, but if it persists, inspection is needed. Turn off power before touching the outdoor unit.

Steps:

• 1. Observe behavior: If H1 appears briefly during heating and then clears, this may be normal defrost operation and not a fault.
• 2. Check outdoor coil: Inspect the outdoor coil for heavy ice buildup. If completely blocked with ice, turn off the unit and allow it to thaw naturally.
• 3. Verify outdoor airflow: Ensure nothing is blocking the outdoor fan or coil (snow, leaves, covers). Clear any obstructions.
• 4. Inspect defrost sensor: If H1 persists and heating is poor, check the outdoor defrost sensor placement and wiring as described under F6.
• 5. Professional service: Persistent H1 with poor heating may indicate refrigerant issues or defrost control problems requiring a technician.