High Lockout
EE4 on Worcester Bosch WR325 RSF

Your boiler is struggling to spark or stay lit, which means your heating and hot water have stopped working.

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

Ignition electrode

What causes this fault?

This fault occurs when the boiler's control system attempts to light the burner but fails to detect a successful flame. The most common reasons are worn-out spark electrodes that can no longer create a strong enough spark or a faulty ignition transformer that isn't providing the necessary electrical pulse to start the combustion process.

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 fault codes

Related guides you might find useful