BoilerFaultCodesThe 5 most common faults
01
Red LED on (solid) High DIY-safe
Your boiler has tried to light but failed to detect a flame, causing it to shut down for safety.
What to try first
Check if other gas appliances, like a hob, are working to confirm gas supply is activeEnsure your gas meter has credit if you use a prepay meterPress and hold the reset button for a few seconds to see if the boiler restarts
02
Red LED after flow switch High DIY-safe
Your boiler has stopped working because water isn't moving through the system correctly, causing it to overheat or fail to detect flow.
What to try first
Check that the boiler pressure is between 1.0 and 1.5 bar on the gaugeEnsure all radiator valves and isolation valves under the boiler are fully openTry resetting the boiler by turning the selector switch to the reset position and back
03
Red LED on (after safety stat) High Engineer
Your boiler has shut down because it grew too hot internally, and for your safety, a permanent lockout has been triggered.
Full guide for Red LED on (after safety stat)04
LED flashing after fan High Engineer
Your boiler has identified a problem with the fan that should be clearing out exhaust fumes, preventing it from starting up safely.
Full guide for LED flashing after fan05
Orange LED flashing High Engineer
Your boiler has detected a problem with the internal temperature sensor that controls your central heating, meaning the system cannot accurately monitor the water temperature.
Full guide for Orange LED flashingon the Sime Planet Dewy BFR
Ignition electrodeFlame sensing probeGas valveIgnition leadCirculation pumpWater flow switch
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 Sime 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