How much does it cost to fix Vaillant error code F.72?

Typical repair cost for the Vaillant F.72 fault is £90-180 including labour.

F.72 High

Vaillant F.72 Fault Code

Q: What does the Vaillant F.72 fault code mean?

Your boiler has detected that the temperature readings between two sensors don't match up, which prevents it from heating your water safely.

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 36 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.

Typical repair cost £90-180 (including labour)

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.

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026