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

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

What this means:
This protection is triggered when the DC bus voltage drops below the minimum threshold, or when a 341 MCE error is detected. This condition can damage the compressor drive circuitry, so the system shuts down to prevent failureTS23.

Try this first (quick reset):

1. Turn off the unit’s power supply.

2. Wait 2 minutes.

3. Turn it back on and check if the error clears.

• If the voltage has returned to normal, the system resumes operation.

• If the error remains — continue with the diagnostic steps.

Next steps (for technicians):

1. Check the AC input voltage (L–N):

   • If low or unstable → correct the power source.

   • If normal → continue.

2. Inspect wiring of power cables and terminals (L/N):

   • Reconnect if any are loose or incorrectly installed.

3. Measure voltage at the input of the bridge rectifier:

   • If not within spec → replace the bridge rectifier.

4. Measure DC voltage between P and N (DC bus):

   • Refer to manufacturer values.

   • If low → continue.

5. Check the PFC module and reactor wiring:

   • If wiring is faulty → reconnect.

   • If reactor or PFC circuit is damaged → replace.

6. Check the IPM board:

   • If faulty → replace the IPM board.

   • If the IPM and PCB are combined → replace the entire outdoor PCB.

What you might need:

• Power supply wires

• Bridge rectifier

• PFC module or reactor

• IPM board

• Outdoor PCB

Helpful tip:
This protection often activates when wiring is poor or the DC power stage components (PFC, rectifier, or reactor) degrade. Begin with voltage checks before replacing hardware.

Click here to view the detailed guide.TS23