High Lockout
133 on Potterton Promax Combi HE Plus

Your boiler has tried to light several times but cannot establish a stable flame, meaning it cannot provide heating or hot water.

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

Interruption of gas supply or ignition failure (spark at ignition electrodes for up to 5 seconds and for 3 attempts)

What causes this fault?

This fault occurs when the boiler fails to detect a flame after several attempts to spark, causing the system to shut down for safety. The most common reasons are a temporary interruption in your gas supply, a build-up of carbon on the ignition probes, or a component failure that prevents gas from flowing correctly into the burner.

This fault is frequently seen during extreme cold snaps, as the external condensate pipe can freeze and back up, preventing the boiler from lighting.

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