Vaillant ecoTEC pro faults
Identify the code and check the version of your boiler.
Models and version of the manual
VMW 236/5-3 and 286/5-3 H-ES. The consulted manual identifies 236/5-3 and 286/5-3 H-ES; the model in the catalog linked here is 286/5-3. The previous mention of 246/5-3, which does not correspond to this edition, is corrected.
Consulted edition: 0020244989_04 · 06/17/2026 · manufacturer's manualThe control options, accessories, and versions may limit which notifications appear in each installation.
Locate the code on your screen.
These accesses lead to their entry in the table. They are not a classification of the most common faults: the manual does not provide incidence statistics.
- F.22
Safety disconnection due to lack of water
- F.28
Fault in ignition start failed
- F.29
Fault in operation: failed ignition
- F.75
Pump fault/lack of water
What to do without opening the boiler
- Note what you see.
Complete code, message, and pressure displayed by the equipment. Indicate whether it occurs when opening hot water, requesting heating, or in both cases.
- Identify the device.
Take a photo of the screen and the identification accessible without disassembling anything. Brand, model, and version help avoid confusing tables from different ranges.
- Describe how it started.
Determine whether the fault is continuous or intermittent and if there was a supply interruption or a recent intervention. If it reappears after a reset allowed by the user manual, do not chain resets.
Do not open the casing or manipulate gas, wiring, combustion, or flue gas outlet. If you smell gas, avoid flames and switches, leave the area, and notify the distributor's emergency service from a safe location; in case of immediate danger, call 112.
Vaillant ecoTEC pro components Manufacturer's diagram
Documented codes table
The meaning of the warning is provided, not the repair operations reserved for qualified personnel. When the manufacturer groups several codes, the grouping is maintained; it is not interpreted as a range of numbers.
| Code | What does it indicate? |
|---|---|
| F.00 | Interruption of the flow temperature sensor |
| F.01 | Interruption of the return temperature sensor |
| F.10 | Short circuit of the supply temperature sensor |
| F.11 | Return temperature sensor short circuit |
| F.20 | Safety temperature limiter disconnection. |
| F.22 | Safety disconnection due to lack of water |
| F.23 | High differential temperature safety disconnection |
| F.24 | Safety lockout due to excessively rapid temperature increase |
| F.25 | Safety disconnect for high gas temperature. |
| F.26 | Fault: combustion valve not working |
| F.27 | Flame simulation safety disconnection |
| F.28 | Fault in ignition start failed |
| F.29 | Fault in operation: failed ignition |
| F.32 | Fan fault |
| F.49 | eBUS fault |
| F.61 | Fuel valve control fault |
| F.62 | Fuel valve disconnection delay fault |
| F.63 | EEPROM fault |
| F.64 | Electronic fault / sensor |
| F.65 | Electronic temp. fault |
| F.67 | Electronic/flame fault |
| F.68 | Fault: unstable flame signal |
| F.70 | Fault: invalid appliance code |
| F.71 | Fault of the flow temperature sensor |
| F.72 | Temperature sensor fault for supply/return |
| F.73 | Water pressure sensor fault (Signal too low) |
| F.74 | Water pressure sensor fault (Signal too high) |
| F.75 | Pump fault/lack of water |
| F.77 | Fault: flue damper/ condensate pump |
| F.78 | Interruption. domestic hot water outlet sensor in external controller. |
| F.83 | NTC fault temperature change. |
| F.84 | Fault NTC: implausible temperature difference |
| F.85 | Fault NTC poorly installed |
No matches found. Please check the code and the version of the equipment.
Is there a problem, but no fault code appears?
The absence of a warning does not rule out a fault. For a boiler that does not heat, does not deliver hot water, loses pressure, or operates intermittently, describe the symptom and the moment it occurs. Do not assume that the PCB, the pump, or a sensor is faulty without checking the equipment and the installation.
Request a review of the boiler. · Consult maintenance
Before requesting a repair
Does the code identify the spare part I need to buy?
No. A single warning can have multiple causes. The spare part reference requires identifying the appliance and confirming the fault; the code or a generic photograph is not sufficient.
Can it be reset again if the fault returns?
It is not advisable to chain resets. Follow only what is outlined for the user in your version's manual. A persistent or recurring lockout requires inspection.
When does it make sense to compare a new boiler?
When you have a diagnosis and a budget, compare repair, availability of the spare part, and replacement according to your installation. An isolated fault code does not justify changing the equipment.
Models of this guide in the catalog
See new boilers · Consult installation or replacement
The technical sheet of each product provides information on its price and availability. Installation is quoted separately depending on the case.
Documentation and other guides
Consult fault guides by brand and model. · Return to the blog