U1 on a Mitsubishi Electric heat pump: Excessive high pressure: high pressure switch (HPS, 15 MPa, N.C., connector CN934) operated
Short answer
On a Mitsubishi Electric heat pump, U1 means: Excessive high pressure: high pressure switch (HPS, 15 MPa, N.C., connector CN934) operated. 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 manual says: Excessive high pressure: high pressure switch (HPS, 15 MPa, N.C., connector CN934) operated.
Part involved: High pressure switch HPS (CN934).
When it shows: Operation of high pressure switch (15 MPa) detected.
Likely causes:
- 1 Water not circulating in outdoor unit water circuit (cylinder unit not filled, air trapped, leak/crushed/blocked pipe, isolating valve closed, cylinder pump valve closed, water pipe frozen, gas cooler blockage); 2 Pump1 in cylinder unit not operating (defective pump1 or cylinder unit board); 3 Defective LEV control from wrong discharge temperature (TH1 loose/defective); 4 Defective LEV coil (loose coil, CN724, disconnection); 5 High pressure switch malfunction/erroneous detection (CN934, terminals, lead wire); 6 Defective outdoor inverter PCB; 7 Defective refrigerant circuit parts (HPS, LEV).
On the Ecodan Hydrodan
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Clogged or broken pipe; 2 Short cycle of refrigerant or ambient loop; 3 Dirty ambient loop heat exchanger; 4 Decreased ambient loop flow rate; 5 Disconnection/contact failure of 63H connector/connection; 6 Defective C.B.; 7 Defective LEV.
On the Ecodan Puhz Sw Split
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Stop valve not fully open; 2 Clogged or broken pipe; 3 Locked outdoor fan motor; 4 Malfunction of outdoor fan motor; 5 Short cycle of outdoor unit; 6 Dirty outdoor heat exchanger; 7 Decreased airflow from outside temperature thermistor reading low; 8 Disconnection/contact failure of 63H connector on outdoor controller board; 9 Disconnection/contact failure of 63H connection; 10 Defective outdoor controller board; 11 Defective action of linear expansion valve; 12 Malfunction of fan driving circuit.
On the Ecodan Puhz W Monobloc
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Decreased water flow; 2 Clogged filter of water pipe; 3 Dirty plate heat exchanger; 4 Locked water pump; 5 Malfunction of water pump; 6 Clogged or broken pipe; 7 Locked outdoor fan motor; 8 Malfunction of outdoor fan motor; 9 Short cycle of outdoor unit; 10 Dirty outdoor heat exchanger; 11 Decreased airflow from low-reading outside thermistor; 12-13 Disconnection/contact failure of 63H connector/connection; 14 Defective outdoor controller board; 15 Defective operation of LEV; 16 Malfunction of fan driving circuit.
On the Ecodan R290 Puz Wz
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (3.2 MPa) during compressor operation.
Likely causes:
- 1 Short cycle / clogged filter / dirty fan or heat exchanger / locked or faulty fan on the indoor side (generic table wording); 2 Clogged or broken pipe; 3 Locked outdoor fan motor; 4 Malfunction of outdoor fan motor; 5 Short cycle of outdoor unit; 6 Dirty outdoor heat exchanger; 7 Decreased airflow from low-reading outside thermistor; 8 Disconnection/contact failure of 63H connector; 9 Disconnection/contact failure of 63H connection; 10 Defective outdoor controller board; 11 Defective action of LEV; 12 Malfunction of fan driving circuit.
On the Ecodan R32 Puz Wm
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Stop valve not fully open; 2 Clogged or broken pipe; 3 Locked outdoor fan motor; 4 Malfunction of outdoor fan motor; 5 Short cycle of outdoor unit; 6 Dirty outdoor heat exchanger; 7 Decreased airflow from outside temperature thermistor reading low; 8 Disconnection/contact failure of 63H connector on outdoor controller board; 9 Disconnection/contact failure of 63H connection; 10 Defective outdoor controller board; 11 Defective action of linear expansion valve; 12 Malfunction of fan driving circuit.
On the Ecodan R32 Zubadan Puz Hwm
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Decreased water flow; 2 Clogged filter of water pipe; 3 Dirty plate heat exchanger; 4 Locked water pump; 5 Malfunction of water pump; 6 Clogged or broken pipe; 7 Locked outdoor fan motor; 8 Malfunction of outdoor fan motor; 9 Short cycle of outdoor unit; 10 Dirty outdoor heat exchanger; 11 Decreased airflow from low-reading outside thermistor; 12 Disconnection/contact failure of 63H connector; 13 Disconnection/contact failure of 63H connection; 14 Defective outdoor controller board; 15 Defective operation of LEV; 16 Malfunction of fan driving circuit.
On the Ecodan Ultra Quiet Puhz W Vaa
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Stop valve not fully open; 2 Clogged or broken pipe; 3 Locked outdoor fan motor; 4 Malfunction of outdoor fan motor; 5 Short cycle of outdoor unit; 6 Dirty outdoor heat exchanger; 7 Decreased airflow from outside temperature thermistor reading low; 8 Disconnection/contact failure of 63H connector on outdoor controller board; 9 Disconnection/contact failure of 63H connection; 10 Defective outdoor controller board; 11 Defective action of linear expansion valve; 12 Malfunction of fan driving circuit.
On the Ecodan Zubadan Puhz Hw Monobloc
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Decreased water flow; 2 Clogged filter of water pipe; 3 Dirty plate heat exchanger; 4 Locked water pump; 5 Malfunction of water pump; 6 Clogged or broken pipe; 7 Locked outdoor fan motor; 8 Malfunction of outdoor fan motor; 9 Short cycle of outdoor unit; 10 Dirty outdoor heat exchanger; 11 Decreased airflow from low-reading outside thermistor; 12-13 Disconnection/contact failure of 63H connector/connection; 14 Defective outdoor controller board; 15 Defective operation of LEV; 16 Malfunction of fan driving circuit.
On the Ecodan Zubadan Puhz Shw Split
The manual says: High pressure (high pressure switch 63H operated during compressor operation).
Part involved: High pressure switch 63H.
When it shows: 63H operates (4.15 MPa) during compressor operation.
Likely causes:
- 1 Stop valve not fully open; 2 Clogged or broken pipe; 3 Locked outdoor fan motor; 4 Malfunction of outdoor fan motor; 5 Short cycle of outdoor unit; 6 Dirty outdoor heat exchanger; 7 Decreased airflow from outside temperature thermistor reading low; 8 Disconnection/contact failure of 63H connector on outdoor controller board; 9 Disconnection/contact failure of 63H connection; 10 Defective outdoor controller board; 11 Defective action of linear expansion valve; 12 Malfunction of fan driving circuit.
Is it safe?
On the Ecodan Co2 Quhz
| 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
| 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
| 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
| 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
| 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
| 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
| 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
| 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
| 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
| 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 (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 the primary circuit pressure gauge (typically about 1-2 bar when cold on sealed systems) and look for visible leaks; do not top up or bleed unless your installer has shown you how and the filling loop is then closed.
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 the primary circuit pressure gauge (typically about 1-2 bar when cold on sealed systems) and look for visible leaks; do not top up or bleed unless your installer has shown you how and the filling loop is then closed.
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
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. Also check from a distance that the outdoor unit air inlet/outlet is not blocked by snow, ice, leaves or other debris (never reach into the fan).
What the engineer will check
On the Ecodan Co2 Quhz
- 1 Check water circuit: fill, bleed air, repair piping/isolating valve/pump valve, melt frozen sections, or replace outdoor unit; 2 Check/replace pump1 or cylinder board; 3 Refit/replace discharge thermistor TH1; 4 Check LEV coil and CN724; 5 Check HPS, CN934, wiring; 6 Replace outdoor inverter PCB; 7 Replace outdoor unit.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / R744 CO2).
Certification: High-pressure CO2 (R744) refrigerant competence (Mitsubishi-trained); F-gas regulation not strictly applicable to R744.
On the Ecodan Hydrodan
- 1 Check piping; 2-3 Check heat pump unit; 4 Check ambient loop flow rate; 5-6 Power off/on and check for F5; 7 Check LEV.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan Puhz Sw Split
- 1 Check stop valve fully open; 2 Check piping; 3-6 Check outdoor unit and repair; 7 Check outside temperature thermistor reading via LED display/SW2; 8-10 Power off/on and check whether F5 is displayed; 11 Check linear expansion valve; 12 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R410A).
On the Ecodan Puhz W Monobloc
- 1-5 Check water circuit and repair; 6 Check piping; 7-10 Check outdoor unit; 11 Check outside thermistor reading (SW2); 12-14 Power off/on and check for F5; 15 Check LEV; 16 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R410A).
On the Ecodan R290 Puz Wz
- 1 Check stop valve fully open; 2 Check piping; 3-6 Check outdoor unit and repair; 7 Check outside temperature thermistor reading via LED display/SW2; 8-10 Power off/on and check whether F5 is displayed; 11 Check linear expansion valve; 12 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification plus competence for flammable A3 refrigerant (R290).
On the Ecodan R32 Puz Wm
- 1 Check stop valve fully open; 2 Check piping; 3-6 Check outdoor unit and repair; 7 Check outside temperature thermistor reading via LED display/SW2; 8-10 Power off/on and check whether F5 is displayed; 11 Check linear expansion valve; 12 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan R32 Zubadan Puz Hwm
- 1-5 Check water circuit and repair; 6 Check piping; 7-10 Check outdoor unit; 11 Check outside thermistor reading (SW2); 12-14 Power off/on and check for F5; 15 Check LEV; 16 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R32, A2L mildly flammable).
On the Ecodan Ultra Quiet Puhz W Vaa
- 1 Check stop valve fully open; 2 Check piping; 3-6 Check outdoor unit and repair; 7 Check outside temperature thermistor reading via LED display/SW2; 8-10 Power off/on and check whether F5 is displayed; 11 Check linear expansion valve; 12 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R410A).
On the Ecodan Zubadan Puhz Hw Monobloc
- 1-5 Check water circuit and repair; 6 Check piping; 7-10 Check outdoor unit; 11 Check outside thermistor reading (SW2); 12-14 Power off/on and check for F5; 15 Check LEV; 16 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R410A).
On the Ecodan Zubadan Puhz Shw Split
- 1 Check stop valve fully open; 2 Check piping; 3-6 Check outdoor unit and repair; 7 Check outside temperature thermistor reading via LED display/SW2; 8-10 Power off/on and check whether F5 is displayed; 11 Check linear expansion valve; 12 Replace outdoor controller board.
Who to ask for: Mitsubishi Ecodan-trained heat pump engineer (refrigeration / F-gas).
Certification: UK F-gas Category I certification (R410A).
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- Keeps stopping / cutting out on the Ecodan R32 Puz Wm: 1 report
Sources
- Ecodan QUHZ-W40VA Service Manual (GHH15010) ↗ · GHH15010 · page 12 · Reviewed 23 September 2026
- Ecodan Hydrodan EHWT17D-MHEDW Installation Manual RK79D203K04 ↗ · RK79D203K04 · page 49 (PDF p.50) · Reviewed 23 September 2026
- Ecodan PUHZ-SW(75-100-120)(V-Y)HA-BS Service Manual (OCH755) ↗ · OCH755 · page OCH755 p.24; OCH525C p.22 · Reviewed 23 September 2026
- Ecodan PUHZ-W112VHA-BS Service Manual (OCH562D) ↗ · OCH562D · page OCH562D p.19; OCH605A p.16; OCH465D p.21; OCH439N p.55 · Reviewed 23 September 2026
- PUZ-WZ(85-100-120)(V-Y)AA(-BS) Service_Manual (OCH880) ↗ · OCH880 · page OCH880 p.38; OCH816 p.34 · Reviewed 23 September 2026
- Ecodan PUZ-WM(50-60-85-112)V(H-A)A Service Manual (OCH727A) ↗ · OCH727A · page 25 · Reviewed 23 September 2026
- Ecodan PUZ-HWM140(V-Y)HA Service Manual (OCH748A) ↗ · OCH748A · page 22 · Reviewed 23 September 2026
- PUHZ-W85-112VAA(-BS) Service Manual (OCH681) ↗ · OCH681 · page 16 · Reviewed 23 September 2026
- Ecodan PUHZ-HW140VHA2-BS / PUHZ-HW140YHA2-BS Service Manual (OCH439N) ↗ · OCH439N · page 55 · Reviewed 23 September 2026
- PUHZ-SHW112-140V/YHA Service Manual (OCH526) ↗ · OCH526 · page 26 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026