B26 High

Johnson Starley B26 Fault Code

The Johnson Starley B26 fault code means: your boiler has detected that the electricity supply coming from the mains is too low for it to operate safely, causing it to temporarily shut down.. It appears on 4 Johnson Starley models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Low mains voltage (Blocking)
Typical repair cost £100-350 (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 B26 fault code

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

Source

Johnson Starley B26 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