High
10.iv on Chaffoteaux Sterling FF

Your boiler is struggling to move heat away from its internal workings, causing it to quickly turn on and off as it tries to protect itself from overheating.

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.

What the manual says

Manufacturer manual

Rapid cycling high/low or high/low/off - Blocked heat exchanger

From this model's manual
Verified against the Chaffoteaux Sterling Ff Combi installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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