BoilerFaultCodesThe 6 most common faults
01
LED 2 High Engineer
Your boiler is struggling to clear air through its internal system effectively enough to safely ignite the burner.
Full guide for LED 202
LED 3 Medium Engineer
Your boiler is signalling that it is asking the internal air extraction motor to speed up to prepare for ignition.
Full guide for LED 303
LED 6 Low DIY-safe
Your boiler is currently going through its normal startup process to ignite the burner and get your heating or hot water working.
What to try first
No action required; this is a normal operational indicator.Monitor the boiler to ensure it completes its startup sequence.If the LED remains frozen or the boiler fails to fire, try a manual reset.
04
LED 1 Low Engineer
Your boiler is currently checking that there is enough airflow for it to start up safely; this light should turn off automatically once the system is ready to fire.
Full guide for LED 105
LED 4 Low Engineer
Your boiler is correctly telling you that it has received a signal from your thermostat and is currently turning on the pump to circulate hot water to your radiators.
Full guide for LED 406
LED 5 Low Engineer
Your boiler is correctly indicating that it has received a request to start the pump for your hot water.
Full guide for LED 5on the Myson Midas 100
Air pressure switchFlue fanVenturi assemblyFan assemblyPrinted Circuit Board (PCB)Main control board
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 Myson 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