Voltage shortage/Overvoltage/PAM error/L1 open phase/Primary current sensor error/Power synchronization signal error

What does 4220 (U9) mean?

This error indicates a problem with the power supply voltage, potentially too low or too high, or an issue with the PAM (Pulse Amplitude Modulation) circuit. It can also point to an open phase on the L1 line in a 3-phase system, or a fault with the primary current sensor.

• Decrease or increase of power supply voltage.
• L1 open-phase (3-phase systems only) or disconnection of compressor wiring.
• Primary current sensor failure or malfunction of the 52C relay.
• Defective outdoor power circuit board or outdoor multi controller circuit board.

Click steps to track your progress.

1. 1

   Turn off the power to the unit before checking any connections or replacing parts.

2. 2

   Check the power supply facility for any abnormalities in voltage or phase (e.g., an L1 open-phase).

3. 3

   Inspect all related wirings, including compressor wiring, for any disconnections or damage.

4. 4

   Ensure the terminal block for the power supply, noise filter circuit board, and power circuit board connections are secure.

5. 5

   If the DC bus voltage does not rise to approximately 380V at PAM driving, check PAM wirings and the reactor for damage.

6. 6

   If the problem persists, the outdoor power circuit board or the outdoor multi controller circuit board may be defective and require professional replacement.