39 Medium

Johnson Starley 39 Fault Code

The Johnson Starley 39 fault code means: your boiler is having a communication error with an external thermostat control, preventing it from heating your home properly.. It appears on 1 Johnson Starley model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Opentherm sensor (if fitted) shorted to earth
Typical repair cost £120-220 (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 39 fault code

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

Source

Johnson Starley 39 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 7 July 2026