U9 on a Mitsubishi Electric heat pump: Abnormal voltage error (see service handbook)

What it means

On the Ecodan Hydrodan

The manual says: Abnormal voltage error (see service handbook).

Part involved: Power supply / outdoor power circuit board / converter.

When it shows: Abnormal voltage detected.

Likely causes:

• See service handbook.

On the Ecodan Puhz Sw Split

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 400 V (SW75/100/120V, SW50VKA), 420 V (SW40/50VHA), 760 V (SW100/120Y) DC bus drops to 200 V (V models) / 350 V (Y models) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) PFC overvoltage/undervoltage/overcurrent (input current 50 A peak on SW75V / SW40-50) DC bus <= 310 V for 10 s while compressor running.

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

On the Ecodan Puhz W Monobloc

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 400 V (V models) DC bus drops to 200 V U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) PFC: DC bus 420 V, PFC control <= 12 V DC, or input current 50 A peak DC bus <= 310 V for 10 s while compressor running.

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

On the Ecodan R290 Puz Wz

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.
• U9 detail 80 - Input voltage sensor error (input voltage >= 290 V or <= 162 V, or open/short in voltage detection circuit).

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 430 V (V models) / 760 V (Y models) DC bus drops to 200 V (V) / 350 V (Y) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit) DC bus <= 310 V for 10 s while compressor running (V models) U9 detail 80 - Input voltage sensor error (input voltage >= 290 V or <= 162 V, or open/short in voltage detection circuit).

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Loose earth wiring; 3 Loose power supply wiring on power/controller board; 4 Defective input voltage signal circuit on outdoor power board.

On the Ecodan R32 Puz Wm

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus voltage rises to 400 V (WM50V), 430 V (WM60/85/112V), 760 V (WM85/112Y) DC bus voltage drops instantaneously to 200 V (V models) / 350 V (Y models) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) PFC detects DC bus 430 V (not WM50V), PFC control voltage <= 12 V DC, or input current increase (V models) DC bus <= 310 V for 10 s while compressor running (V models only).

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

On the Ecodan R32 Zubadan Puz Hwm

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 430 V (V) / 760 V (Y) DC bus drops to 200 V (V) / 400 V (Y) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) PFC: DC bus 460 V, PFC control <= 12 V DC, or input current 74 A peak.

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.

On the Ecodan Ultra Quiet Puhz W Vaa

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus to 430 V (W85V/W112V) / 760 V (Y) DC bus drops to 200 V (V) / 350 V (Y) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit) DC bus <= 310 V for 10 s while compressor running (W85V, W112V only).

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

On the Ecodan Zubadan Puhz Hw Monobloc

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 400 V (HW140V) / 760 V (HW112/140Y) DC bus drops to 200 V (HW140V) / 350 V (HW112/140Y) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) PFC: DC bus 420 V, PFC control <= 12 V DC (input-current trip 50 A peak on W50V only) DC bus <= 310 V for 10 s while running (W50-85V / HW140V only).

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

On the Ecodan Zubadan Puhz Shw Split

The manuals for this range word it in different ways:

• Abnormality of voltage (inverter power supply abnormality; detailed sub-codes 01-80 identify the cause).
• U9 detail 01 - Overvoltage error: increase in DC bus voltage.
• U9 detail 02 - Undervoltage error: instantaneous decrease in DC bus voltage.
• U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A).
• U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz).
• U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit).
• U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Part involved: Power supply / outdoor power circuit board / converter; Outdoor power circuit board / power supply.

When it shows: Power supply / DC bus voltage abnormality detected by inverter; read detail history with SW2-1, 2-2, 2-6 ON DC bus rises to 400 V (SHW80/112VHA) / 760 V (SHW112/140YHA) DC bus drops to 200 V (VHA) / 350 V (YHA) U9 detail 04 - Input current sensor error / L1-phase open error: input current falls to 0.1 A while running (>= 40 Hz or compressor current >= 6 A) U9 detail 08 - Abnormal power synchronous signal (no signal, or <= 44 Hz / >= 65 Hz) U9 detail 10 - PFC error (overvoltage / undervoltage / overcurrent detected by power factor correction circuit) U9 detail 20 - PFC/IGBT error (undervoltage): DC bus voltage <= 310 V for 10 s while compressor running.

Likely causes:

• See detailed sub-codes: overvoltage, undervoltage, input current sensor / L1-phase open, power synchronous signal, PFC/IGBT errors. General: compressor wiring, supply voltage, CN52C/CNAF wiring.
• 1 Abnormal increase in power source voltage; 2 Disconnection of compressor wiring; 3 Defective outdoor power circuit board; 4 Compressor ground fault.
• 1 Decrease in power source voltage / instantaneous stop; 2 Defective converter drive circuit on outdoor power board (V models); 3 Defective 52C drive circuit on power board; 4 Defective converter board / rush current resistor RS (Y models); 5 Loose CN2 between power and controller boards (V); 6 Failure of 15 V DC supply on controller board (V).
• 1 L1-phase open (3-phase Y models); 2 Loose wiring TB1-noise filter board (Y); 3 Loose CN5/CNCT (Y); 4 Defective ACCT current transformer; 5 Defective input current detection circuit on power board; 6 Defective outdoor controller board.
• 1 Distortion of power source voltage / noise; 2 Disconnection or loose earth wiring; 3 Loose CN2 between power and controller boards; 4 Defective sync signal circuit on controller board; 5 Defective sync signal circuit on power board.
• 1 Abnormal increase in source voltage; 2 Decrease in source voltage / instantaneous stop; 3 Disconnection of compressor wiring; 4 Misconnection of reactor (DCL); 5 Defective outdoor power board; 6 Defective reactor; 7 Loose CN2.
• 1 Incorrect model-select switch settings on outdoor controller board; 2 Defective outdoor power circuit board; 3 Defective outdoor controller board.

Is it safe?

The heat pump stops until the fault clears or is reset.

Resetting itself: Not stated as auto-recovering in the service manual; code is logged in the outdoor unit error history.

Manual reset: Clear via RESET on the main remote controller after the cause is fixed; service manual actions include switching power off and on to recheck.

What you can check

On the Ecodan Hydrodan

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.

On the Ecodan Puhz Sw Split

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan Puhz W Monobloc

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan R290 Puz Wz

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan R32 Puz Wm

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan R32 Zubadan Puz Hwm

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan Ultra Quiet Puhz W Vaa

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan Zubadan Puhz Hw Monobloc

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

On the Ecodan Zubadan Puhz Shw Split

• Note the code, unit and ref. address shown on the main remote controller and contact your installer (Mitsubishi user manuals: 'Make a note of the error code number and contact installer'). Check the heat pump breaker/isolator at the consumer unit is on and read the primary system pressure gauge (if fitted) so you can report it. A single reset from the main remote controller (RESET, then Yes) may be tried; if the code returns, do not keep resetting. Do not open the outdoor unit, cylinder/hydrobox or any casing. Check that the heat pump's dedicated breaker/isolator (and, where fitted, the separate indoor-unit supply) is switched on; if it trips again, leave it off.
• Note the code, unit and ref. address shown on the main remote controller and contact your installer. Do not reset repeatedly: this is an electrical/compressor protection code. If the breaker or RCD has tripped, or there is a burning smell, leave the heat pump switched off at its isolator and call an engineer. Do not open any casing.

What the engineer will check

On the Ecodan Hydrodan

• See service handbook.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan Puhz Sw Split

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan Puhz W Monobloc

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan R290 Puz Wz

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check power supply wiring; 4 Replace outdoor power board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan R32 Puz Wm

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan R32 Zubadan Puz Hwm

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan Ultra Quiet Puhz W Vaa

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan Zubadan Puhz Hw Monobloc

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

On the Ecodan Zubadan Puhz Shw Split

• 1 Check compressor wiring; 2 Check compressor winding resistance; 3 Check supply voltage; 4 Check CN52C wiring; 5 Check CNAF wiring; read U9 detail code (SW2-1, SW2-2, SW2-6 ON) and follow sub-code action.
• 1 Check field power supply; 2 Correct compressor wiring (U-V-W); 3 Replace outdoor power circuit board; 4 Check compressor insulation, replace compressor.
• 1 Check field power supply; 2-3 Replace outdoor power circuit board; 4 Replace converter board / check RS wiring or replace RS (Y); 5 Check CN2 wiring; 6 Replace outdoor controller board.
• 1 Check field power supply (all phases); 2-3 Check wiring TB1-noise filter board and CN5/CNCT; 4 Replace noise filter board; 5 Replace power board; 6 Replace controller board.
• 1 Check field power supply; 2 Check earth wiring; 3 Check CN2 wiring; 4 Replace outdoor controller board; 5 Replace outdoor power board.
• 1-2 Check field power supply; 3 Correct compressor wiring; 4 Correct reactor wiring; 5 Replace power board; 6 Replace reactor; 7 Check CN2 wiring.
• 1 Correct model select switches; 2 Replace power board; 3 Replace controller board.

Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).

Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.

What you might notice

• Intermittent fault
• No heating
• Tripping RCD or breaker

What owners and engineers report

1 owner and engineer report mentions this.

• Intermittent fault on the Ecodan Ultra Quiet Puhz W Vaa: 1 report

Sources

• Ecodan Hydrodan EHWT17D-MHEDW Installation Manual RK79D203K04 ↗ · RK79D203K04 · page 51 (PDF p.52) · Reviewed 23 September 2026
• Ecodan PUHZ-SW(75-100-120)(V-Y)HA-BS Service Manual (OCH755) ↗ · OCH755 · pages OCH755 p.26-27; OCH525C p.24, OCH755 p.26; OCH525C p.24, OCH755 p.27; OCH525C p.24 · Reviewed 23 September 2026
• Ecodan PUHZ-W112VHA-BS Service Manual (OCH562D) ↗ · OCH562D · pages OCH562D p.21; OCH605A p.18; OCH465D p.23; OCH439N p.57-58, OCH562D p.21 · Reviewed 23 September 2026
• PUZ-WZ(85-100-120)(V-Y)AA(-BS) Service_Manual (OCH880) ↗ · OCH880 · pages OCH880 p.40-41; OCH816 p.36-37, OCH880 p.40; OCH816 p.36, OCH880 p.41; OCH816 p.37, OCH880 p.41 · Reviewed 23 September 2026
• Ecodan PUZ-WM(50-60-85-112)V(H-A)A Service Manual (OCH727A) ↗ · OCH727A · pages 27-28, 27, 28 · Reviewed 23 September 2026
• Ecodan PUZ-HWM140(V-Y)HA Service Manual (OCH748A) ↗ · OCH748A · page 24 · Reviewed 23 September 2026
• PUHZ-W85-112VAA(-BS) Service Manual (OCH681) ↗ · OCH681 · pages 18-19, 18, 19 · Reviewed 23 September 2026
• Ecodan PUHZ-HW140VHA2-BS / PUHZ-HW140YHA2-BS Service Manual (OCH439N) ↗ · OCH439N · pages 57-58, 57, 58 · Reviewed 23 September 2026
• PUHZ-SHW112-140V/YHA Service Manual (OCH526) ↗ · OCH526 · pages 28-29, 28, 29 · Reviewed 23 September 2026

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026