ADC LOCKOUT High

Johnson Starley ADC LOCKOUT Fault Code

Also written as ADCLOCKOUT — same fault.

The Johnson Starley ADC LOCKOUT fault code means: your boiler's computer brain is having trouble processing information from its internal sensors and has shut down for safety.. It appears on 2 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: Analog to digital converter lockout
Typical repair cost £220-450 (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 ADC LOCKOUT fault code

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

Source

Johnson Starley ADC LOCKOUT 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