Compressor Overcurrent or Power Module Error

What it means

This code appears on the wired remote of Mitsubishi Electric Mr. Slim ducted, ceiling and cassette units. It means the outdoor inverter board detected a sudden overcurrent in the compressor circuit or a fault in the power module (IPM) that drives it. The unit stops the compressor at once to protect the electronics and windings, and there is no cooling until the cause is removed. The same code can mean something else on other brands, and wall-mounted Mitsubishi Electric models show errors as lamp blinks with a different meaning.

Models covered: Mitsubishi Electric ducted, ceiling and cassette units (Mr. Slim) with check codes on the wired remote; wall-mounted Mitsubishi Electric models may show errors as lamp blinks with a different meaning.

Related codes: UPU5E6U1

Symptoms4

• The outdoor unit stops as the compressor starts, or seconds later, and U6 appears.
• A clicking sound or failed start attempt from the compressor.
• The code returns with every start attempt.
• In severe cases the breaker trips.

Possible causes5

• Closed service valves or unequal pressures at start-up.
• Loose, burned or wrongly ordered compressor wiring terminals.
• Severe voltage fluctuation or low supply voltage.
• A failed power module (IPM) or outdoor inverter board.
• A mechanically or electrically failed compressor (damaged windings or a seized compressor).

How to diagnose6

1. Turn the unit off at the breaker and do not keep restarting it, as this can add damage.
2. Note whether the code appeared together with a power cut or voltage swings.
3. Switch off at the breaker before opening any panel; the outdoor unit and its inverter board keep a dangerous charge for a while after switch-off.
4. The technician confirms the service valves are open and the compressor terminals are sound and in the correct order.
5. The technician measures supply voltage and tests the power module and inverter board using the manufacturer method.
6. The technician tests the compressor windings and insulation, then decides whether the board or the compressor is at fault.

How to fix6

1. Open the service valves fully if they were closed.
2. Tighten or replace burned compressor terminals and correct their order.
3. Fit a voltage protector and fix the supply problem.
4. Replace the inverter board or power module at an authorized service center.
5. Replace the compressor if proven faulty, with evacuation and recharge by a licensed technician.
6. Run the system, monitor current and confirm the code does not return.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a closed valve or a loose terminal, rises steeply for an inverter board, and is highest for an inverter compressor.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions