A Hitachi Yutaki error code is an alarm number the heat pump shows when one of its safety or monitoring checks fails. It appears on the remote control switch, usually as a plain number such as 03 or 104. Some water-side alarms carry a P in front, so you may see P70, P83 or P74 instead.
This guide covers the Yutaki S, S Combi, S80 and M, though not every code applies to every model. For other makes, see our guide to heat pump error codes.
One safety line before anything else: switch the unit off at its isolator before you go near it, and never open the casing. If a code keeps coming back, or you are not sure what it means, book an engineer. We handle Hitachi heat pump repairs across the UK.
Please read first: this guide is here to help you understand what your Hitachi heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and codes can differ between models and software versions, so always check the official Hitachi manual for changes before acting on anything here. Do not attempt anything that could be dangerous, and avoid any work that could void your warranty. If in doubt, call a qualified heat pump engineer.
If your Hitachi Yutaki heat pump is not showing a code, or you want to rule out the basics first, our guide to air source heat pump problems and fixes walks through the general checks and matches common faults to error codes across every major brand.
Is it safe to fix a Hitachi heat pump fault yourself?
Only up to a point: basic outside checks are fine, but anything inside the unit is a job for a qualified engineer. You can read the pressure gauge, check valves are open, clear leaves or snow from the outdoor unit and reset a tripped breaker once.
Never remove panels or touch the electrics inside either unit.
Refrigerant work is restricted by law to F-Gas certified engineers, so any code pointing at refrigerant pressure or discharge temperature is not a DIY job. Unauthorised work inside the unit can also affect your manufacturer warranty, so check your paperwork before anyone else touches it.
Which Hitachi error codes can you check yourself?
A handful of Hitachi codes have a realistic homeowner check, mostly the water pressure, flow, airflow and communication alarms. Everything else needs an engineer. Codes marked * appear in the Yutaki S80 documents only, so check your manual.
| Code | What it means | Safe homeowner check | Stop and call an engineer if |
|---|---|---|---|
| 83 / P83 | Water pressure not detected | Read the gauge. If you have a filling loop and your manual allows it, top up to the figure your installer gave you | Pressure drops again within days, or you see water anywhere |
| 70 / P70 | No water flow, or pump fault | Check the isolation valves near the unit and radiator valves are open | The code returns, or the pump hums or rattles |
| 35*, 38*, 51* | Overload or fin temperature, often linked to a blocked outdoor coil | Clear leaves, snow and debris from around the outdoor unit, by hand only | The coil is iced solid or the fan is not turning |
| 03, 63 | Communication between units has failed | Check the heat pump breakers at the consumer unit are on | A breaker trips again straight away |
| 77* | Opentherm thermostat signal lost | Check the room thermostat has power or fresh batteries | The code persists with a working thermostat |
| 78* | Wireless (RF) devices not responding | Replace batteries in wireless thermostats and check receivers are powered | Devices still will not reconnect |
| 80* | Controller cable signal lost | Switch off at the isolator, wait a few minutes and restart once | It comes straight back, which points to wiring |
What are the most common Hitachi heat pump error codes?
The Hitachi codes we see most are the water flow and pressure alarms (70 and 83), followed by sensor faults and refrigerant pressure trips. Under each code, the Hitachi meaning comes first. Causes marked "general" come from engineering experience, not the manual.
70 / P70: water flow or pump alarm
Hitachi says the unit cannot detect water flow, or the pump is defective. General causes include a blocked strainer, a closed valve, an air lock or sludge in the circuit. Scale inside the plate heat exchanger can restrict flow too.
What to do: check the valves are open and look at the pressure gauge. If it returns, an engineer will clean the strainer, bleed the system and test the pump. Older radiator systems with heavy sludge may need a heat pump powerflush.
83 / P83: water pressure alarm
Hitachi says water pressure is not detected in the circuit. In general, that means pressure has dropped through a leak or a failing expansion vessel, or the pressure sensor itself has failed.
What to do: top up only if you have a filling loop and the manual allows it. If the pressure falls again, there is a leak to find. Our guide to a heat pump losing pressure explains where to look.
74 / P74: unit over-temperature
Hitachi says the supply temperature stayed 5 degrees above the circuit maximum for 20 seconds. Generally this follows poor flow or a stuck mixing valve, and it is an engineer fix.
72: thermostat heater alarm
Hitachi says high temperature was detected in the electric backup heater. The general cause is low flow or an air lock around the heater, so an engineer should bleed the circuit and check flow.
11 to 19, 23 and 25: thermistor (sensor) faults
These codes mean a temperature sensor connector is loose, disconnected, broken or short-circuited. Examples are the water inlet (11), water outlet (12) and hot water tank (16) sensors. An engineer will check the plug and measure the sensor's resistance before replacing anything.
03 and 63: communication faults
Code 03 means the outdoor and indoor units have stopped talking, often from a blown outdoor fuse or a damaged or miswired cable. Code 63 is the same fault between a central controller and the indoor unit. Check your breakers once, then leave it to an engineer.
35 and 38: overload with a blocked outdoor coil
These S80 codes point to a blocked heat exchanger, with a broken outdoor fan or closed expansion valve also listed. In winter, the general cause is often ice that the defrost cycle has not cleared. If the coil stays iced, read our guide to a frozen outside unit and call us.
101: high pressure switch
On the S80, code 101 means refrigerant pressure went above 3.0 MPa and the high pressure switch tripped. General causes are poor water flow or a scaled heat exchanger, so heat is not being taken away fast enough. This needs an F-Gas engineer.
104 and 105: low pressure
Code 104 means suction pressure fell below 0.15 MPa for 1.5 minutes. Code 105 means the pressure ratio stayed below 1.8 for 3 minutes. General causes are refrigerant loss or an iced coil, and both need an F-Gas engineer.
08 and 106: high discharge temperature
Code 08 is a compressor-top temperature alarm. Hitachi lists refrigerant shortage, clogged piping or a locked fan as causes. Code 106 trips at 120 degrees for 10 minutes or over 140 degrees for 5 seconds; both are F-Gas engineer jobs.
Which error code might you see in common situations?
What is happening around the house is often the best clue. Codes marked * are listed for the Yutaki S80 only.
| Situation | Codes you may see on a Hitachi | First check |
|---|---|---|
| Cold snap and iced outdoor unit | 104*, 35*, 38*, 51* | Let a defrost finish, then clear snow from around the unit. Never chip at ice on the fins |
| Losing pressure or low pressure | 83 / P83 | Read the gauge and look for drips under the indoor unit and radiators |
| Radiators lukewarm | 70 / P70, 73 | Check radiator and isolation valves are open and the pressure is normal |
| No hot water | 16, 72 | Check the hot water schedule on the controller, then note the code |
| After a power cut | 03, 05, 06, 134* | Wait until the supply is stable, then restart once at the isolator |
| Unit noisy or fan not spinning | 57*, 08, 07 | Look for ice, leaves or debris around the fan without reaching inside |
| After a service or filter clean | 70 / P70, 83 / P83 | Confirm valves were reopened and the pressure was restored |
Cool radiators with no code are covered in heat pump not heating, and new rattles or hums in heat pump making noise.
How do you reset a Hitachi heat pump?
Hitachi does not publish a homeowner reset sequence for the Yutaki range, so the safe option is a simple power restart. Switch off at the isolator or breaker, wait a few minutes, then switch back on. If the code returns, write it down and call an engineer.
Resetting over and over without fixing the cause is a bad idea. Protection alarms such as 101, 104 and 106 exist to stop the compressor running in conditions that damage it. Forcing restarts can turn a small repair into a big one.
Hitachi error code list
This list covers the alarm codes published for the Yutaki S, S Combi, S80 and M ranges. Codes marked * appear in S80 documents only, and not every code applies to every model, so check your manual.
| Code | Meaning | Who should fix it |
|---|---|---|
| 02 | Outdoor protection device (high pressure) activated | F-Gas engineer |
| 03, 04 | Outdoor to indoor or inverter transmission error | Engineer |
| 05, 06, 134* | Power phase, voltage or supply phase fault | Engineer |
| 07 | Discharge gas superheat falling | F-Gas engineer |
| 08 | Compressor-top temperature too high | F-Gas engineer |
| 11 to 19, 23, 25, 125* | Temperature sensor (thermistor) faults | Engineer |
| 22, 24, 40 | Capacity, unit number or controller setting error | Engineer |
| 31* | Outdoor protection detection circuit fault (one third-party source lists a capacity mismatch, so check your manual) | Engineer |
| 35* | Pump down overload (one third-party source lists an indoor setting error, so check your manual) | Homeowner check, then F-Gas engineer |
| 38* | Heating overload | Homeowner check, then F-Gas engineer |
| 41*, 42* | Suction pressure and overload protection | F-Gas engineer |
| 47*, 48*, 53* | Inverter current sensor, module or not operating | Engineer |
| 51* | Inverter fin temperature fault | Homeowner check, then engineer |
| 57* | DC fan motor protection | Engineer |
| 63 | Central controller to indoor transmission error | Engineer |
| 70 / P70 | No water flow or pump fault | Homeowner check, then engineer |
| 72, 73, 74 / P74 | Backup heater, mixed circuit or unit over-temperature | Engineer |
| 77*, 78* | Opentherm or wireless (RF) communication failure | Homeowner check |
| 80* | Controller cable (H-LINK) signal lost | Homeowner check, then engineer |
| 83 / P83 | Water pressure not detected | Homeowner check |
| 101*, 104*, 105* | High or low refrigerant pressure | F-Gas engineer |
| 106* | Discharge gas temperature too high | F-Gas engineer |
| 129*, 130* | Refrigerant pressure sensor faults | F-Gas engineer |
Where can you find the official Hitachi manual?
Hitachi publishes its Yutaki manuals and technical catalogues on its official documentation site, with a page for each range. Use the page for your model, as alarm lists differ between ranges.
- Hitachi Yutaki S80 manuals and technical catalogues
- Hitachi Yutaki S manuals and technical catalogues
- Hitachi Yutaki S Combi manuals and technical catalogues
- Hitachi Yutaki M R32 manuals and technical catalogues
Need help with a Hitachi heat pump fault?
We repair Hitachi heat pumps across the UK, from the Yutaki S and S Combi to the S80 and M. Our engineers are F-Gas certified and we are MCS accredited, so refrigerant faults are covered as well as water-side ones.
We start with proper fault diagnosis, reading the alarm and testing the part behind it, then carry out the heat pump repair it needs. Our work comes with a 12-month guarantee. If you have no heating in cold weather, our emergency heat pump repair team offers same-day visits where possible.
Many of the codes above, especially the flow, pressure and coil alarms, are less likely on a unit that is looked after. Annual heat pump servicing catches blocked strainers, falling pressure and dirty coils early, and our cover plans spread the cost.
Call us on 0333 041 5130 or contact us online to book.
Frequently asked questions
Does a Hitachi error code void my warranty?
No, a code on its own does not affect your warranty. What can affect it is work inside the unit by someone unqualified, or missed servicing if your terms require it. Check your warranty documents before booking anyone.
Does a refrigerant pressure code mean the compressor has failed?
Not usually. Codes such as 101 and 104 are often triggered by poor water flow, an iced coil or refrigerant loss, with the compressor shutting down to protect itself. An engineer will measure pressures and temperatures before blaming the compressor, and our guide to heat pump compressor problems explains the warning signs.
What should I note down before calling an engineer?
Write down the exact code, including any P prefix, and when it appeared. Add a photo of the controller and the model label, as code lists differ between the Yutaki S, S Combi, S80 and M.
How long does a Hitachi heat pump repair take?
Sensor, wiring and flow faults are often fixed in a single visit. If a part such as a board or pump has to be ordered, a second visit is likely. Refrigerant leaks take longer, as the leak has to be found and tested before the system is recharged.
Can a Hitachi code clear itself?
It can, depending on the alarm and what caused it, though Hitachi's documents do not say which codes clear on their own. A code that disappears after power returns or flow recovers has not necessarily been fixed. If the same code shows up more than once in a week, book a visit rather than waiting for it to stick.
