BoilerFaultCodesThe 6 most common faults
01
Display not illuminated High DIY-safe
Your boiler has lost all power and is completely switched off, meaning you currently have no heating or hot water.
What to try first
Check that the main boiler on/off switch is in the 'on' position.Look at your home's fuse box or consumer unit to ensure the circuit breaker for the heating system hasn't tripped.Verify that the fused spur connection unit (usually a white switch with a fuse) near the boiler is switched on and that the fuse itself has not blown.
02
Lockout High Engineer
Your boiler has detected a safety fault and has stopped working to prevent further issues, meaning you currently have no heating or hot water.
Full guide for Lockout03
Flashing High Engineer
Your boiler has detected a fault and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.
Full guide for Flashing04
Sensor High Engineer
Your boiler's temperature sensor is providing incorrect information, causing the system to stop operating correctly to ensure safety.
Full guide for Sensor05
Flow sensor High Engineer
Your boiler is struggling because a small internal sensor that tracks water movement has been dislodged or is not seated correctly.
Full guide for Flow sensor06
Dry fire High Engineer
Your boiler has detected that it is running without enough water inside, meaning it cannot safely heat your home.
Full guide for Dry fireon the Potterton Envoy Plus
PCB (Printed Circuit Board)External fuse or fused spurTransformerIgnition 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 Potterton 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