E403 (Red ON, Green Blink, Yellow OFF) — Outdoor freezing detected when compressor stops

What does E403 mean?

The outdoor unit's PCB LED displays E403 when it detects freezing conditions on the outdoor coil, even though the compressor is not running. This suggests an issue with the outdoor condenser or refrigerant flow.

• Ice buildup on outdoor condenser coils
• Restricted airflow to the outdoor unit
• Refrigerant issues (e.g., undercharge, overcharge)
• Dirty indoor unit filters

Click steps to track your progress.

1. 1

   Visually inspect the outdoor unit for any signs of ice, snow, or debris blocking the condenser coils. Clear any obstructions.

2. 2

   Check and clean the air filters in all indoor units to ensure proper airflow through the system.

3. 3

   Turn off the main power to the unit at the circuit breaker and allow any ice to melt naturally (if present).

4. 4

   Restore power and attempt to restart the system. If the error recurs, contact a qualified technician to check refrigerant levels and piping.