BoilerFaultCodesJohnson Starley F37 Fault Code
The Johnson Starley F37 fault code means: your boiler has detected that there is not enough water pressure in the system to operate safely, which has caused it to shut down.. It appears on 7 Johnson Starley models in our database.
Technical description: Low water pressure
DIY fix possible
Locate the filling loop (a flexible silver hose) underneath or near the boiler.Open the small valves on the filling loop slowly until you hear water entering the system.Watch the pressure gauge and close the valves when the needle reaches between 1.0 and 1.5 bar.Restart the boiler to clear the fault code.
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Gas Safe Register →Johnson Starley models that show the F37 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Johnson Starley F37 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