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 45 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.
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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
- 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 612
- ecoFIT pure 615
- ecoFIT pure 618
- ecoFIT pure 630
- ecoFIT Pure 825 Repair: £150-250
- ecoFIT Pure 830 Repair: £180-350
- ecoFIT Pure 835 Repair: £150-250
- ecoFIT sustain 415
- ecoFIT sustain 418
- ecoFIT sustain 430
- ecoFIT sustain 615
- ecoFIT sustain 618
- ecoFIT sustain 630
- ecoFIT sustain 825
- ecoFIT sustain 830
- ecoFIT sustain 835
- ecoTEC Repair: £140-£220
- ecoTEC 65kW Repair: £150-300
- ecoTEC exclusive Repair: £140-£260
- ecoTEC exclusive 627
- ecoTEC plus 612
- ecoTEC plus 618
- ecoTEC Plus 620 Repair: £120-200
- ecoTEC plus 624
- ecoTEC Plus 625 Repair: £120-200
- ecoTEC Plus 630 Repair: £120-200
- ecoTEC Plus 635 Repair: £120-200
- ecoTEC plus 637 Repair: £140-£220
- ecoTEC Plus 826 Repair: £180-350
- ecoTEC Plus 832 Repair: £120-200
- ecoTEC Plus 840 Repair: £120-200
- ecoTEC Plus 938 Repair: £120-200
- 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 Combi Repair: £150-250
- 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.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoFIT pure 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026