How much does it cost to fix Johnson Starley error code b33?

Typical repair cost for the Johnson Starley b33 fault is £140-£260 including labour.

b33 High

Johnson Starley b33 Fault Code

Q: What does the Johnson Starley b33 fault code mean?

Your boiler has detected an issue with the sensor that monitors water movement, meaning it cannot properly manage the temperature or flow of your heating.

Also written as B33 — same fault.

The Johnson Starley b33 fault code means: your boiler has detected an issue with the sensor that monitors water movement, meaning it cannot properly manage the temperature or flow of your heating.. It appears on 1 Johnson Starley model in our database.

Technical description: Flow sensor fault

Typical repair cost £140-£260 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Johnson Starley models that show the b33 fault code

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

Warmcair DW Repair: £140-£260

Source

Johnson Starley b33 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