High Lockout
B(3) on Potterton Flamingo RS40 RS50

Your boiler's small starter flame is either too weak or not staying lit, which is preventing the main burner from firing up to provide heat.

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

Pilot rate too low.

What causes this fault?

This fault occurs when the small pilot flame remains too small or weak to heat the safety sensor properly. The most common reasons are a tiny piece of debris blocking the pilot jet or a failing thermocouple that can no longer detect the heat of the flame, causing the boiler to shut down for safety.

This issue often appears after the boiler has been turned off for the summer, as dust and debris can settle in the pilot assembly during periods 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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Related fault codes

B(1)View →B(2)View →

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