Common problems guide

The most common Chaffoteaux Sterling FF problems

The faults most likely to send a Chaffoteaux Sterling FF into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
37 documented codes
6 most common
3 DIY-safe checks
3 engineer needed

The 6 most common faults

01
12 High DIY-safe

Your boiler has stopped working because the water pressure inside your heating system has dropped too low.

What to try first

Locate the filling loop (usually a silver braided hose with one or two valves) underneath the boiler.Open the valve(s) slowly to allow water into the system while watching the pressure gauge.Close the valve(s) tightly once the needle reaches the green zone, typically between 1.0 and 1.5 bar.

Est. cost
£80-150
Parts
Filling loop, Pressure relief valve, Expansion vessel
Full guide for 12
02
2a High DIY-safe

Your boiler has stopped working because the amount of water inside the heating system has dropped too low.

What to try first

Locate the external filling loop, which is a silver braided hose usually found underneath the boiler.Open the small valve(s) on the loop to let water in until the pressure gauge on the front of the boiler reads between 1 and 1.5 bar.Close the valve(s) tightly once the correct pressure is reached.

Est. cost
£0-80
Parts
Pressure gauge, Filling loop, Pressure relief valve
Full guide for 2a
03
6.iii High DIY-safe

Your boiler has stopped working because it cannot detect enough water pressure inside the system to operate safely.

What to try first

Locate your boiler's filling loop (the silver braided hose under the unit)Slowly open the valves on the loop to let water into the systemWatch the pressure gauge on the front until the needle reaches 1.5 bar, then securely close the valves

Est. cost
£80-150
Parts
Pressure relief valve, Pressure sensor, Expansion vessel
Full guide for 6.iii
04
Red High Engineer

Your boiler has detected a fault and stopped working for safety reasons, meaning you currently have no heating or hot water.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, Printed circuit board
Full guide for Red
05
Lock out radiator light High Engineer

Your boiler has failed to light the gas flame and has safely shut itself down to prevent any risk.

Est. cost
£120-250
Parts
Ignition electrode, Gas valve, PCB
Full guide for Lock out radiator light
06
13 High Engineer

Your boiler pressure is rising too high because water is leaking into the system when it shouldn't be, which could cause a leak or pipe burst.

Est. cost
£120-250
Parts
Filling loop, Plate heat exchanger
Full guide for 13
Parts most often replaced

on the Chaffoteaux Sterling FF

Filling loopPressure relief valveExpansion vesselPressure gaugePressure sensorIgnition electrode

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Chaffoteaux shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 37-code list for the Chaffoteaux Sterling FF

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →