BoilerFaultCodesVaillant F.74 Fault Code
Also written as F74 — same fault.
The Vaillant F.74 fault code means: your boiler has detected a problem with the sensor that monitors water pressure, meaning it cannot accurately tell if there is enough water in the system to run safely.. It appears on 33 Vaillant models in our database.
Technical description: Water pressure sensor signal outside correct range, the sensor signal is too high
What causes the Vaillant F.74 fault?
This fault occurs when the boiler's internal computer receives an electrical signal from the water pressure sensor that is completely outside of its expected range. The most common reason is that the sensor itself has developed an internal electrical short or has become blocked with system debris, causing it to send a false high-voltage reading. In some cases, a damaged or damp wiring harness can also interfere with the signal being sent to the main control board.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vaillant models that show the F.74 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £130-210
- Combi Compact 242EB Repair: £140-£260
- Combi Compact 282EB Repair: £140-£220
- ecoFIT pure Repair: £150-250
- ecoFIT Pure 412 Repair: £150-250
- ecoFIT Pure 418 Repair: £150-250
- ecoFIT Pure 425 Repair: £150-250
- ecoFIT Pure 435 Repair: £150-250
- ecoFIT Pure 825 Repair: £150-250
- ecoFIT Pure 830 Repair: £180-350
- ecoFIT Pure 835 Repair: £150-250
- ecoTEC Repair: £140-£220
- ecoTEC exclusive Repair: £140-£260
- ecoTEC plus Repair: £120-200
- ecoTEC Plus 615 Repair: £120-200
- ecoTEC Plus 620 Repair: £120-200
- ecoTEC Plus 625 Repair: £120-200
- ecoTEC Plus 630 Repair: £120-200
- ecoTEC Plus 635 Repair: £120-200
- ecoTEC Plus 65 Repair: £120-200
- ecoTEC Plus 826 Repair: £180-350
- ecoTEC Plus 832 Repair: £120-200
- ecoTEC Plus 836 Repair: £120-200
- ecoTEC Plus 840 Repair: £120-200
- ecoTEC Plus 938 Repair: £120-200
- ecoTEC plus System Repair: £150-250
- ecoTEC Pro Repair: £100-220
- ecoTEC Pro / ecoTEC Plus Repair: £140-£220
- ecoTEC Pro 24 Repair: £100-220
- ecoTEC Pro 28 Repair: £100-220
- ecoTEC Pro 30 Repair: £150-250
- ecoTEC sustain Repair: £120-200
- Home System Repair: £140-£220
Source
Vaillant F.74 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026