BoilerFaultCodesVaillant F.73 Fault Code
Also written as F73 — same fault.
The Vaillant F.73 fault code means: your boiler is unable to accurately measure the water pressure because the internal sensor is sending an incorrect or missing signal.. It appears on 45 Vaillant models in our database.
Technical description: Water pressure sensor signal in the wrong range, it is too low
What causes the Vaillant F.73 fault?
This fault occurs when the boiler's internal computer receives an electrical signal from the water pressure sensor that is outside of its expected operating range. The most common reason is a physical failure of the sensor itself, though it can also be caused by loose or damaged wiring that prevents the sensor from communicating correctly. As a safety precaution, the boiler stops running because it cannot confirm there is enough water to operate safely.
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.73 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £130-220
- 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: £150-250
- 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: £150-250
- ecoTEC exclusive Repair: £140-£250
- ecoTEC exclusive 627
- ecoTEC plus 612
- ecoTEC plus 618
- ecoTEC Plus 620 Repair: £130-220
- ecoTEC plus 624
- ecoTEC Plus 625 Repair: £130-220
- ecoTEC Plus 630 Repair: £130-220
- ecoTEC Plus 635 Repair: £130-220
- ecoTEC plus 637 Repair: £140-£250
- ecoTEC Plus 826 Repair: £150-250
- ecoTEC Plus 832 Repair: £130-220
- ecoTEC Plus 840 Repair: £130-220
- ecoTEC Plus 938 Repair: £130-220
- ecoTEC Pro Repair: £140-£220
- ecoTEC Pro / ecoTEC Plus Repair: £140-£250
- ecoTEC Pro 24 Repair: £140-£220
- ecoTEC Pro 28 Repair: £140-£220
- ecoTEC Pro 30 Repair: £150-250
- ecoTEC sustain Repair: £130-220
- Home Combi Repair: £150-250
- Home System Repair: £140-£220
Source
Vaillant F.73 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