High Lockout
LED 1 Slow Flashing (2Hz) on Glow-worm Micron 60FF

Your boiler has entered a safety lockout mode because it failed to light or stay on properly after multiple attempts.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Non - Volatile Lockout

What causes this fault?

This fault occurs when the boiler's control system detects that a flame has not been successfully established or maintained after several ignition cycles. The most common reasons include a worn-out spark probe that can no longer ignite the gas, or a faulty gas valve preventing fuel from reaching the burner.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →