Medium
10.i on Chaffoteaux Sterling FF

Your boiler is struggling because it cannot pump enough water through the system, causing it to rapidly turn on and off to protect itself.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Rapid cycling high/low or high/low/off - Low water flow rate

DIY fix possible

Check your central heating pressure gauge and top it up to 1.5 bar if lowEnsure all radiator valves are fully openCheck that your external pump speed setting has not been turned down

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