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Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: February 7, 2024. Updated: May 17, 2024

F72 Vaillant Fault Code – How to fix

The Vaillant boiler F72 fault code signals an issue with the NTC thermistors. These are essential for regulating water temperature, leading to automatic boiler shutdown.

Professional intervention by a Gas Safe registered engineer is mandatory. Costs for repairs will vary by location and the nature of the fault.

Understanding F72

The F72 error code is triggered by discrepancies in the readings from the flow and return NTC thermistors (sensors). It can also be triggered when the boiler perceives a problem with these components.

These thermistors play a vital role in the boiler’s ability to regulate water temperature accurately.

Causes of Incorrect NTC Thermistor Readings

Several factors can lead to faulty readings from the NTC thermistors, including:

  • Faulty Thermistors: These components can fail due to defects present from installation or deterioration over time.
  • Wiring Fault: Issues in the wiring between the thermistors and the PCB can disrupt communication and lead to incorrect temperature regulation.
  • Poor Installation: Incorrectly installed thermistors can cause misreadings, although this is less common due to post-installation checks.

Professional Repair is Necessary

Given the complexity and safety concerns associated with boiler repairs, addressing an F72 fault is not a DIY task. Hiring a Gas Safe registered engineer is legally required to ensure the problem is diagnosed and resolved correctly and safely.

Cost Breakdown

The cost of hiring a heating engineer varies significantly across different UK cities, with average hourly rates ranging from £30 to £95. The total cost of resolving an F72 fault, including labour and parts, can vary widely depending on the specific repair needed:

  • Replacing one thermistor: £50 to £200
  • Replacing two thermistors: £70 to £250
  • Fixing a wiring fault: £60 to £220 (may require an electrician)
  • Correcting poor installation: £40 to £180
  • Whole new boiler: £2,100 to £3,400

Warranty Considerations

Whether an F72 fault repair is covered under warranty depends on the fault’s cause being linked to a manufacturing error and the warranty’s active status and terms.


In conclusion, while an F72 fault code can be concerning. The boiler should be off due to the error. Contact a Gas Safe registered engineer to repair your boiler as soon as you can.

Unfortunately, your boiler may be unrepairable. If this is the case, get a boiler replacement quote for a premium boiler with Boilerhut:

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