High Lockout
C(5) on Potterton Flamingo RS40 RS50

Your boiler is unable to light because the small nozzle that delivers gas to the main burner has become clogged with debris.

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

Blocked main burner injector

What causes this fault?

This fault occurs when microscopic debris or carbon deposits build up inside the tiny hole that sprays gas into the main burner. Over time, these particles block the flow entirely, meaning the boiler can no longer create the flame needed to heat your water or radiators.

This fault is more common when you first turn the heating on in autumn, as debris can settle and harden within the burner components during the summer months of inactivity.

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.

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