UP on a Mitsubishi Electric heat pump: Overcurrent abnormality: overcurrent detected by secondary current
Short answer
On a Mitsubishi Electric heat pump, UP means: Overcurrent abnormality: overcurrent detected by secondary current. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 10 sources
What it means
On the Ecodan Co2 Quhz
The manuals for this range word it in different ways:
- Overcurrent abnormality: overcurrent detected by secondary current.
- Abnormality of circuit to detect AC current: defective primary current detection sensor for 2 minutes.
- Service mode end display: service mode (outdoor run with compressor relay connector CN61 disconnected) continued for 20 minutes.
Part involved: Compressor / outdoor inverter PCB / LEV; Outdoor inverter PCB current sensor; Compressor relay connector CN61 / outdoor inverter PCB.
When it shows: Overcurrent detected by secondary current Defective primary current detection sensor detected continuously for 2 minutes Service mode continued for 20 minutes.
Likely causes:
- 1 Defective compressor lead wire relay connector/terminal connection; 2 Defective outdoor inverter PCB (Q821, IC700, overcurrent detection circuit); 3 Defective LEV coil; 4 Defective LEV unit (locked, foreign matter); 5 Defective compressor (coil short/open, locked); 6 Power waveform distortion, noise.
- 1 Defective outdoor inverter PCB.
- 1 Compressor relay connector disconnected; 2 Defective outdoor inverter PCB.
On the Ecodan Hydrodan
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- See service handbook.
On the Ecodan Puhz Sw Split
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Looseness, disconnection or reverse of compressor wiring; 3 Defective outdoor fan; 4 Short cycle of outdoor unit; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Defective outdoor power circuit board; 8 DIP switch (model select) setting difference on outdoor controller board.
On the Ecodan Puhz W Monobloc
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Compressor wiring loose/reversed; 3 Defective outdoor fan; 4 Short cycle; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Decreased water flow; 8 Clogged water filter; 9 Clogged plate HEX; 10 Locked water pump; 11 Malfunction of water pump.
On the Ecodan R290 Puz Wz
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Looseness, disconnection or reverse of compressor wiring; 3 Defective outdoor fan; 4 Short cycle of outdoor unit; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Defective outdoor power circuit board; 8 DIP switch (model select) setting difference on outdoor controller board.
On the Ecodan R32 Puz Wm
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Looseness, disconnection or reverse of compressor wiring; 3 Defective outdoor fan; 4 Short cycle of outdoor unit; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Defective outdoor power circuit board; 8 DIP switch (model select) setting difference on outdoor controller board.
On the Ecodan R32 Zubadan Puz Hwm
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Compressor wiring loose/reversed; 3 Defective outdoor fan; 4 Short cycle; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Decreased water flow; 8 Clogged water filter; 9 Clogged plate HEX; 10 Locked water pump; 11 Malfunction of water pump.
On the Ecodan Ultra Quiet Puhz W Vaa
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Outdoor stop valve closed; 2 Decrease of power supply voltage; 3 Compressor wiring loose/reversed; 4 Defective fan; 5 Short cycle; 6 Defective input circuit of outdoor controller board; 7 Defective compressor; 8 Defective outdoor power board; 9 DIP switch setting difference.
On the Ecodan Zubadan Puhz Hw Monobloc
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Compressor wiring loose/reversed; 3 Defective outdoor fan; 4 Short cycle; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Decreased water flow; 8 Clogged water filter; 9 Clogged plate HEX; 10 Locked water pump; 11 Malfunction of water pump.
On the Ecodan Zubadan Puhz Shw Split
The manual says: Compressor overcurrent interruption: overcurrent of DC bus or compressor after 30 seconds of compressor operation.
Part involved: Compressor / outdoor power & controller boards.
When it shows: Overcurrent of DC bus or compressor detected after compressor has run 30 s.
Likely causes:
- 1 Decrease of power supply voltage; 2 Looseness, disconnection or reverse of compressor wiring; 3 Defective outdoor fan; 4 Short cycle of outdoor unit; 5 Defective input circuit of outdoor controller board; 6 Defective compressor; 7 Defective outdoor power circuit board; 8 DIP switch (model select) setting difference on outdoor controller board.
Is it safe?
On the Ecodan Co2 Quhz
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated as auto-recovering.
Manual reset: Outdoor error cancelled by switching the cylinder unit earth leakage circuit breaker OFF, waiting until the outdoor board LEDs go out (about 1 minute), then ON again (service manual GHH15010).
On the Ecodan Hydrodan
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan Puhz Sw Split
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan Puhz W Monobloc
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan R290 Puz Wz
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan R32 Puz Wm
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan R32 Zubadan Puz Hwm
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan Ultra Quiet Puhz W Vaa
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan Zubadan Puhz Hw Monobloc
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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.
On the Ecodan Zubadan Puhz Shw Split
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
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 Co2 Quhz
- 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.
- 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.
On the Ecodan Hydrodan
- 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 Sw Split
- 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. 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. 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. 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. 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. 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. 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. 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 Co2 Quhz
- 1 Check continuity of compressor and lead wires, reconnect relay connector/terminal (breaker OFF first); 2 Replace outdoor inverter PCB; 3 Check LEV coil/CN724; 4-5 Replace outdoor unit; 6 Check power waveform.
- 1 Replace the outdoor inverter PCB.
- 1 Turn cylinder unit earth leakage breaker OFF before reconnecting compressor relay connector; 2 Replace outdoor inverter PCB.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics); Mitsubishi Ecodan-trained heat pump engineer (controls / wiring).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience.
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; UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan Puhz Sw Split
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R410A).
On the Ecodan Puhz W Monobloc
- 1 Check power supply; 2 Correct compressor wiring; 3 Check outdoor fan; 4 Solve short cycle; 5 Replace outdoor controller board (check U-V-W output first); 6 Check compressor; 7-11 Check water circuit and repair.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R410A).
On the Ecodan R290 Puz Wz
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification plus competence for flammable A3 refrigerant (R290).
On the Ecodan R32 Puz Wm
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan R32 Zubadan Puz Hwm
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan Ultra Quiet Puhz W Vaa
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R410A).
On the Ecodan Zubadan Puhz Hw Monobloc
- 1 Check power supply; 2 Correct compressor wiring; 3 Check outdoor fan; 4 Solve short cycle; 5 Replace outdoor controller board (check U-V-W output first); 6 Check compressor; 7-11 Check water circuit and repair.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R410A).
On the Ecodan Zubadan Puhz Shw Split
- 1 Check power supply; 2 Correct compressor wiring (U-V-W); 3 Check fan; 4 Solve short cycle; 5 Replace outdoor controller board (first check U-V-W output voltages are balanced with compressor disconnected); 6 Check compressor; 7 Replace outdoor power circuit board; 8 Check DIP switch settings.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (electrical / inverter diagnostics).
Certification: Competent electrician (BS 7671 / Part P); heat pump inverter experience; UK F-gas Category I certification (R410A).
What you might notice
What owners and engineers report
2 owner and engineer reports mention this.
- Heat pump will not start on the Ecodan Puhz W Monobloc: 1 report
- Keeps stopping / cutting out on the Ecodan R32 Puz Wm: 1 report
Sources
- Ecodan QUHZ-W40VA Service Manual (GHH15010) ↗ · GHH15010 · page 15 · Reviewed 23 September 2026
- 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 · page OCH755 p.28; OCH525C p.25 · Reviewed 23 September 2026
- Ecodan PUHZ-W112VHA-BS Service Manual (OCH562D) ↗ · OCH562D · page OCH562D p.22; OCH605A p.19; OCH465D p.24; OCH439N p.59 · Reviewed 23 September 2026
- PUZ-WZ(85-100-120)(V-Y)AA(-BS) Service_Manual (OCH880) ↗ · OCH880 · page OCH880 p.42; OCH816 p.38 · Reviewed 23 September 2026
- Ecodan PUZ-WM(50-60-85-112)V(H-A)A Service Manual (OCH727A) ↗ · OCH727A · page 29 · Reviewed 23 September 2026
- Ecodan PUZ-HWM140(V-Y)HA Service Manual (OCH748A) ↗ · OCH748A · page 25 · Reviewed 23 September 2026
- PUHZ-W85-112VAA(-BS) Service Manual (OCH681) ↗ · OCH681 · page 20 · Reviewed 23 September 2026
- Ecodan PUHZ-HW140VHA2-BS / PUHZ-HW140YHA2-BS Service Manual (OCH439N) ↗ · OCH439N · page 59 · Reviewed 23 September 2026
- PUHZ-SHW112-140V/YHA Service Manual (OCH526) ↗ · OCH526 · page 30 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026