High Lockout
FAIL POINT J on Worcester Bosch 24/28CDi II RSF

Your boiler has failed to ignite properly, meaning it cannot create the flame needed to provide you with heat or hot water.

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

Flashing fast

What causes this fault?

This fault occurs when the boiler attempts to start up but cannot establish a stable flame to stay running. The most common reasons include a blockage in the gas supply, worn-out spark electrodes that can no longer ignite the fuel, or a control board that isn't sending the correct signals to the gas valve.

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 →

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →