How much does it cost to fix Johnson Starley error code 34?

Typical repair cost for the Johnson Starley 34 fault is £100-350 including labour.

34 High

Johnson Starley 34 Fault Code

Q: What does the Johnson Starley 34 fault code mean?

Your boiler has detected that the electricity supply coming into your home is too low for it to operate safely and has shut down to protect its components.

The Johnson Starley 34 fault code means: your boiler has detected that the electricity supply coming into your home is too low for it to operate safely and has shut down to protect its components.. It appears on 10 Johnson Starley models in our database.

Technical description: Low mains supply voltage

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 34 fault code

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

Source

Johnson Starley 34 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