Sensor codes (10 to 58)
A temperature sensor is short-circuited or cut. The boiler often keeps working in a degraded way, with poorer comfort or no hot water.
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Viessmann Error Codes
A Viessmann Vitodens or Vitola showing a two-character code such as F2, EE or A8? Look it up in the table below. Viessmann codes mix digits and letters (10, 30, b7, F9…) and some only appear in the fault history. Our engineers repair Viessmann gas and oil boilers 7 days a week and always give the price before the repair.
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ViessmannVitodens and Vitola
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Fault historyRead on site
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Viessmann boiler breakdowns we fix
Viessmann boilers are common in Belgian houses: the wall-hung Vitodens condensing gas boilers (100-W, 200-W, 222-F…) and the floor-standing Vitola or Vitorondens oil boilers. Each family has its own panel and its own way of displaying faults.
Ignition codes EE and EF, overheating F2 and the pump code A8 make up most of our call-outs. Sensor codes (10, 18, 30, 38, 50…) are less urgent but still change how the boiler behaves: with a broken outdoor sensor, for instance, it heats as if it were freezing outside.
The engineer reads the fault history, tests the suspected parts and tells you the price before replacing anything. Electrodes, sensors and common spares travel with him.
Viessmann service and combustion check
On a Vitodens, a service includes cleaning the heat exchanger and the burner, inspecting the electrodes and the condensate siphon, and measuring the combustion. A clean boiler gives far fewer EE or F1 codes.
At the end of the visit you receive the service attestation. Code 0F, which you may notice in the history, is just the reminder that this service is due.
Viessmann error code table
Enter the code shown on the panel. Codes with two digits relate to sensors, codes starting with E or F to the burner, codes starting with b to the electronics.
| Code | Meaning | What the technician checks |
|---|---|---|
| 10 | Outdoor temperature sensor short circuit: the boiler regulates as if it were 0 °C outside | Outdoor sensor and its cable. |
| 18 | Outdoor temperature sensor open circuit: the boiler regulates as if it were 0 °C outside | Outdoor sensor and its cable. |
| 19 | Communication lost with the wireless (RF) outdoor sensor | Wireless sensor and radio link. |
| 0F | Service due (shown only in the fault history) | Annual boiler service. |
| 20 / 28 | System flow temperature sensor (low loss header) short circuit / open circuit | Sensor and wiring. |
| 30 / 38 | Boiler temperature sensor short circuit / open circuit — burner locked out | Boiler sensor and wiring. |
| 40 / 48 | Heating circuit 2 (with mixing valve) flow sensor short circuit / open circuit | Circuit 2 sensor and wiring. |
| 44 / 4C | Heating circuit 3 (with mixing valve) flow sensor short circuit / open circuit | Circuit 3 sensor and wiring. |
| 50 / 58 | Domestic hot water sensor short circuit / open circuit — no hot water | Hot water sensor and cable. |
| A3 | Flue gas temperature sensor incorrectly positioned — burner locked out | Position and fitting of the flue gas sensor. |
| A8 | Air in the internal circulation pump or minimum flow rate not reached (automatic venting programme) | System pressure, air in the circuit, internal pump. |
| A9 | Internal circulation pump blocked | Internal circulation pump. |
| b0 / b8 | Flue gas temperature sensor short circuit / open circuit | Flue gas sensor and wiring. |
| b1 | Programming unit communication fault | Programming unit and its connection. |
| b5 | Internal control unit fault | Control unit. |
| b7 | Boiler coding card fault — burner locked out | Coding card. |
| E3 | Heat transfer too low during calibration — the high limit safety cut-out has tripped | Heat take-up by the heating circuit, radiator valves, pump. |
| EE | No flame signal, or signal too weak, when the burner starts | Gas supply, ionisation electrode, gas valve. |
| EF | Flame lost just after ignition | Gas supply, ionisation electrode, flue gas recirculation. |
| F1 | The flue gas temperature limiter has responded | Fouling of the heat exchanger, flue gas sensor. |
| F2 | The high limit safety cut-out has responded (overheating) | Water circulation, system pressure, pump, heat exchanger. |
| F3 | Flame signal already present when the burner starts | Ionisation electrode, control unit. |
| F8 | The fuel (gas) valve does not close | Gas valve and flame detection; the boiler stays off until repaired. |
| F9 / FA | Fan speed too low / not reached | Fan and wiring. |
| FC | Faulty gas combination valve or blocked flue gas path | Gas combination valve, flue. |
| Fd | Burner control unit fault | Burner control unit, ignition, electrodes. |
| FE | Circuit board EEPROM error or coding card missing | Circuit board, coding card. |
| FF | Internal fault or R button stuck | Control unit, unlock button. |
Code not in this table: call us, our technician knows it.
Smell of gas? Do not touch any switch, open the windows, leave the house and call 112 from outside. For any other code, write it down and call us: the technician knows what to look at and brings the right parts.
Three groups of Viessmann codes
Burner codes (E, F)
Ignition, flame, overheating, fan or gas valve. These stop the burner and need a diagnosis on site.
Electronics codes (b, FE, FF)
Control unit, coding card or programming unit. The engineer tests the electronics before ordering a part.
What our customers say
Where do we work?
We repair and service Viessmann boilers across the whole of Belgium, in Brussels, Wallonia and Flanders. Ring us to hear when a heating engineer can be with you.
BrusselsWalloon BrabantFlemish BrabantHainautNamurLiègeLuxembourg provinceAntwerpEast FlandersWest FlandersLimburg
The brands we work with
Our technicians work on all brands: they install, service and repair appliances from the major manufacturers. For a new installation, we recommend the model that suits your home and budget.
We buy our equipment from all the major Belgian wholesalers and suppliers, including Facq, Van Marcke and Desco: genuine parts, quickly available.
Frequently asked questions
What does F2 mean on a Viessmann boiler?
The high limit safety cut-out has tripped: the water in the boiler got too hot. Poor circulation, a pump problem or low pressure are typical causes, found by the technician on site.
What do EE and EF mean?
EE: no flame signal (or too weak) at start-up. EF: the flame went out just after ignition. Both concern the gas supply, the ionisation electrode or the gas valve.
My Vitodens shows A8: what is it?
The boiler has detected air in its internal pump or too little flow and runs a venting programme. If the code returns, the circuit and the pump need to be examined.
Code 10 or 18 on the display: is the boiler broken?
No, the outdoor sensor is faulty. The boiler keeps heating, but as if it were 0 °C outside. The sensor or its cable is replaced.
What should I do with code F8?
Leave the boiler off and call us: F8 means the gas valve does not close properly. It must be repaired before the boiler is used again.
Do you work on Viessmann oil boilers?
Yes, on Vitola and Vitorondens oil boilers as well as Vitodens gas boilers, for both repairs and servicing.
Your Viessmann shows a code?
Call us or pick a time online: a heating engineer comes over with his measuring equipment.