BoilerFaultCodesVaillant F.72 Fault Code
Also written as F72 — same fault.
The Vaillant F.72 fault code means: your boiler has detected that the temperature readings between two sensors don't match up, which prevents it from heating your water safely.. It appears on 28 Vaillant models in our database.
Technical description: Flow return NTC error – temperature difference too great
What causes the Vaillant F.72 fault?
This fault occurs when the boiler's control board detects that the temperature readings from the flow and return pipes don't match up logically, suggesting one of the sensors is faulty or out of calibration. Essentially, the boiler can no longer trust the data it is receiving about how hot the water is, so it shuts down as a safety precaution. While it is usually a sensor failure, it can occasionally be caused by a wiring issue between the sensors and the main control unit.
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.72 fault code
Click a model for the full fault code list and model-specific repair notes.
- Atmomax Repair: £100-220
- 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 825 Repair: £150-250
- ecoFIT Pure 830 Repair: £150-250
- ecoFIT Pure 835 Repair: £150-250
- ecoTEC Repair: £90-160
- ecoTEC 65kW Repair: £150-300
- ecoTEC exclusive Repair: £120-£220
- ecoTEC Plus 610 Repair: £150-300
- ecoTEC Plus 615 Repair: £120-220
- ecoTEC Plus 620 Repair: £120-220
- ecoTEC Plus 625 Repair: £120-220
- ecoTEC Plus 630 Repair: £120-220
- ecoTEC Plus 635 Repair: £120-220
- ecoTEC Plus 826 Repair: £150-250
- ecoTEC Plus 840 Repair: £120-220
- ecoTEC Plus 938 Repair: £120-220
- ecoTEC Pro Repair: £120-£220
- ecoTEC Pro / ecoTEC Plus Repair: £90-180
- ecoTEC Pro 24 Repair: £120-£220
- ecoTEC Pro 28 Repair: £120-£220
- ecoTEC Pro 30 Repair: £150-300
- ecoTEC sustain Repair: £120-220
- Home Combi Repair: £150-£300
- Home System Repair: £90-180
Source
Vaillant F.72 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 412 manual (PDF)
- Vaillant ecoFIT Pure 835 manual (PDF)
- Vaillant ecoTEC manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026