Error Code: PC 31 – System Low Pressure Protection

Error Code: PC 31 – System Low Pressure Protection

What this means:
This error occurs when the outdoor pressure switch detects that the system’s low pressure has dropped below 0.13 MPa. The unit shuts down to prevent compressor damage due to insufficient refrigerant, airflow issues, or pressure switch faultsTS36.

Try this first (quick reset):

1. Power off the system completely.

2. Wait 2 minutes.

3. Restart and observe the display.

• If the error clears — continue monitoring system pressure.

• If the error returns — proceed with the diagnostics below.

Next steps (for technicians):

1. Check wiring between low pressure protector and main PCB:

   • If loose or incorrect → reconnect properly.

   • If connected correctly → continue testing.

2. Measure resistance of the low pressure switch:

   • Disconnect the plug.

   • If resistance ≠ 0 → replace the low pressure protector.

   • If resistance = 0 → continue to next step.

3. Check ambient outdoor temperature:

   • If it’s too low → shut down the system temporarily.

4. Verify high pressure valve core is open:

   • If closed → open the valve core.

5. Check indoor fan operation (in cooling mode):

   • If not running → refer to “Fan Speed Out of Control” troubleshooting (e.g., EC 07).

6. Check refrigerant system:

   • If undercharged → add refrigerant.

   • If refrigerant level is normal but error persists → replace outdoor PCB.

What you might need:

• Low pressure protector

• Outdoor PCB

• Connection wires

• Additional refrigerant

Helpful tip:
This is a common issue after installation or during cold weather. Always check valve positions and refrigerant levels before replacing hardware.

Click here to view the detailed guide.TS36