How much does it cost to fix Johnson Starley error code F40?

Typical repair cost for the Johnson Starley F40 fault is £80-180 including labour.

F40 High

Johnson Starley F40 Fault Code

Q: What does the Johnson Starley F40 fault code mean?

Your boiler has shut down because there is too much water pressure in the system, which can put unnecessary strain on the internal seals and pipework.

The Johnson Starley F40 fault code means: your boiler has shut down because there is too much water pressure in the system, which can put unnecessary strain on the internal seals and pipework.. It appears on 7 Johnson Starley models in our database.

Technical description: Water pressure too high

Typical repair cost £80-180 (including labour)

DIY fix possible

Check the filling loop handles are fully closedBleed water from a radiator using a bleed key to reduce pressureMonitor the pressure gauge until it returns to between 1 and 1.5 barPress the reset button if the fault remains displayed

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Johnson Starley models that show the F40 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Johnson Starley F40 fault code information on this page is sourced and cross-checked against the official Johnson Starley service / installation manuals for each affected model.

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