Error Code: PC 12 – Outdoor Main Board DC Bus Low Voltage Protection / 341 MCE Error

Error Code: PC 12 – Outdoor Main Board DC Bus Low Voltage Protection / 341 MCE Error

What this means:
The system has detected that the DC voltage on the outdoor unit’s main board has dropped too low. This may prevent the inverter from operating and can trigger a protection shutdown to avoid system instability.

Try this first (quick reset):

1. Turn off the power completely.

2. Wait 2 full minutes.

3. Turn the system back on and check if the error disappears.

• If the error clears — the issue may have been temporary.

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

Next steps (for technicians):

1. Verify power supply:

   • Ensure stable AC voltage input (typically 220–400V).

   • If voltage is unstable or too low, correct the supply before further testing.

2. Check wiring and terminals:

   • Confirm all power wiring and connectors are properly installed and in good condition.

   • Repair or replace if faulty.

3. Measure DC voltage between terminals P and N:

   • In standby, voltage should be ~310V, 340V, or 380V depending on the model.

   • If it’s significantly lower → confirms DC bus under-voltage.

4. Component testing and replacement:

   • If voltage is too low:

     • Replace the IPM module board.

     • If issue persists, test the reactor.

     • If the reactor is functioning properly, replace the outdoor PCB.

What you might need:

• IPM module board

• Outdoor PCB

• Reactor

• Power supply wires

Helpful tip:
DC bus low voltage can result from grid undervoltage, poor grounding, faulty capacitors, or loose wire connections. Always verify supply voltage and wiring before swapping parts.

Click here to view the detailed guide.TS10-S