7H-01
Not enough water flow.
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Daikin Altherma Error Codes: 7H-01, U4-00 and the Other Codes
In short: on an Altherma 3 the code is made of two characters and two figures: the first say which part is in fault, the last give the cause. A technician comes and gives the price first. Call 0477 03 88 98.
Is your Daikin Altherma heat pump showing a code such as 7H-01 or U4-00? Below you will find what each code means, what you can check yourself and what the technician looks at.
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Daikin AlthermaAir-to-water
Indoor unitAnd outdoor unit
Price firstBefore the repair
22 yearsIn the trade
A Daikin Altherma in fault
The Daikin Altherma is one of the most widely installed air-to-water heat pumps in Belgium: Altherma 3 R, Altherma 3 H HT to replace a boiler on radiators, monobloc or split, with a wall-hung indoor unit or a floor-standing unit with a built-in tank.
A heat pump constantly monitors the water flow, the temperatures, the communication between the two units and the refrigerant circuit. The most common code is 7H-01, a lack of water flow. U4-00 reports that the indoor and outdoor units no longer talk to each other, 89-02 a frozen exchanger.
Our technician checks the flow, the strainer, the pump, the sensors, the power to both units and, if needed, the refrigerant circuit. He explains the cause and tells you what the repair costs before doing it.
Codes 7H-01 to E1-00
7H-01 — Water flow problem in the heating circuit. Pressure, air, valves, strainer, circulating pump.
80-00 — Problem with the return water temperature sensor. Return sensor and wiring.
81-00 — Problem with the flow water temperature sensor. Flow sensor and wiring.
89-02 — Heat exchanger frozen (outside defrost). Water flow in cold weather, frost protection, settings.
8H-00 — Abnormal rise of the flow water temperature. Flow rate, flow sensor, electric back-up heater.
AA-01 — Electric back-up heater overheated. Back-up heater safety device, water flow, contactors.
E1-00 — Outdoor unit board fault. Outdoor unit board, power supply.
These codes apply to the Daikin Altherma 3; older Altherma units may show slightly different codes. Always note the two figures after the dash.
Codes E3-00 to U5-00
E3-00 — High pressure switch tripped. Water flow, refrigerant circuit, heat exchanger.
E7-00 — Outdoor unit fan motor fault. Fan, blocked unit, board.
H9-00 — Outdoor temperature sensor fault. Outdoor unit sensor and wiring.
HC-00 — Domestic hot water sensor fault. Tank sensor and wiring.
U0-00 — Probable lack of refrigerant. Tightness of the refrigerant circuit, leak search.
U2-00 — Abnormal supply voltage. Electrical supply of the outdoor unit.
U4-00 — Communication lost between indoor and outdoor unit. Outdoor unit power, interconnection cable, boards.
U5-00 — Problem communicating with the user interface. Controller, controller cable, indoor unit board.
Your code is not listed? Call us: the technician knows it.
Servicing a Daikin heat pump
Many Altherma codes come from a lack of servicing: a dirty strainer (7H-01), an outdoor unit full of leaves (E7-00), settings that do not match the house.
During the service the technician cleans the strainer of the water circuit, checks the pressure and the expansion vessel, cleans the outdoor coil, checks the electrical connections and notes the operating values.
He also looks at the fault history in the controller: he can see whether a code comes back on cold nights and adjusts the settings so that the heat pump works in good conditions.
Typical faults
Water flow (7H-01): a dirty strainer, air in the circuit, a closed valve or a tired pump. Communication (U4-00, U5-00): an outdoor unit without power, a damaged interconnection cable or a faulty board.
Frost (89-02): too little flow in cold weather, the exchanger freezes and the unit protects itself. Keep the heat pump powered so that its frost protection keeps working.
Back-up heater (AA-01): the electric element overheated, often because of the flow. Refrigerant (U0-00): a small leak lowers performance and then stops the unit.
What the technician does
He reads the fault history: the controller keeps the last codes with their time, so he sees what happens at night and in cold weather.
He measures both circuits: flow and pressure of the water circuit, temperatures and, if needed, the refrigerant pressures. Then come the price, the repair, the adjustment of the controls, the job sheet and the invoice.
A heat pump contains refrigerant under pressure and live parts: only a technician should open the indoor or outdoor unit.
Codes we see most
U4-00
No communication between units.
89-02
Frozen exchanger.
AA-01
Back-up heater overheated.
When you call
The full code
For example 7H-01.
The model
Altherma 3 R, H HT…
The pressure
Of the water circuit.
When
Day, night, in frost.
How we work
Phone, WhatsApp or online
Use whichever suits you and tell us your neighbourhood.
Time confirmed
You know when the technician will come and what the call-out costs in advance.
Nothing without your OK
Work starts once you have said yes. Keep the job sheet and the invoice for your records.
What our customers say
Where we work
We repair and service Daikin heat pumps across Belgium, in Brussels, Flanders and Wallonia.
BrusselsWalloon BrabantFlemish BrabantHainautNamurLiègeLuxembourgAntwerpEast FlandersWest FlandersLimburg
Frequently asked questions
What does code 7H-01 mean on a Daikin Altherma?
The water flow in the heating circuit is too low. The strainer, air in the installation, a valve or the pump can be the cause: note the code and call us.
What does U4-00 mean?
The indoor unit no longer communicates with the outdoor unit. The power to the outdoor unit, the interconnection cable or a board needs checking.
My Altherma shows 89-02 in frosty weather: what do I do?
The exchanger has frozen and the unit is protecting itself. Keep the heat pump powered and call us: the cause is often a flow that is too low.
Is code AA-01 serious?
The electric back-up heater overheated and its safety device cut out. The cause has to be found before it goes back into service: that is a job for the technician.
Do you service Daikin heat pumps?
Yes: water circuit strainer, outdoor unit, connections, operating values and controller settings.
When can you come?
We offer the first free slot, depending on your municipality, with the price given first.
How do I book?
Call 0477 03 88 98, send us a WhatsApp message or book online with the « Book an appointment » button. Tell us the municipality and, in a few words, what is going on.
Is your Daikin Altherma showing a code?
Call 0477 03 88 98 or book online: a technician comes to check your heat pump.