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

Book a service

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

What the manual says

Manufacturer manual

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

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.

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

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like 10.i: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

10View →

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →