BoilerFaultCodesThe 6 most common faults
01
08 High DIY-safe
Your boiler has stopped because the water pressure inside the system has dropped too low to operate safely.
What to try first
Locate the filling loop (usually a silver braided hose with one or two valves underneath the boiler).Slowly open the valve(s) to allow mains water into the system until the pressure gauge on the front reads between 1.0 and 1.5 bar.Close the valve(s) tightly and restart the boiler.
02
Red lockout indicator bulb High Engineer
Your boiler has failed to light the flame, so it has safely shut itself down to prevent a gas buildup.
Full guide for Red lockout indicator bulb03
40 High Engineer
Your boiler has detected that it is getting too hot and has temporarily paused its operation to prevent damage.
Full guide for 4004
Red indicator High Engineer
Your boiler has stopped working because it cannot light its internal flame to heat your water.
Full guide for Red indicator05
Red lockout indicator bulb 29 High Engineer
Your boiler has failed to light the flame three times, so it has purposefully shut itself off for your safety.
Full guide for Red lockout indicator bulb 2906
80 High Engineer
Your boiler has detected a communication error between its internal electronic control systems, causing the system to stop operating.
Full guide for 80on the Chaffoteaux Calydra 100
Pressure relief valveFilling loopPressure sensorIgnition electrodeGas valvePrinted Circuit Board (PCB)
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