BoilerFaultCodesThe 3 most common faults
01
Lockout High DIY-safe
Your boiler has stopped working for safety reasons and needs to be physically reset to try and start again.
What to try first
Turn the selector knob to the Reset position for 5 secondsTurn the knob back to your preferred settingWait to see if the burner ignites and the light stops flashing
02
Sensor Faults High Engineer
Your boiler has detected that a temperature monitoring sensor is providing incorrect readings or has stopped working, meaning the unit cannot safely manage its heat output.
Full guide for Sensor Faults03
Reverse polarity High Engineer
Your boiler is failing to start because the electrical supply wires have been connected in the wrong order, preventing the system from safely powering up.
Full guide for Reverse polarityon the Ideal British Gas RD
Ignition electrodeGas valvePrinted Circuit BoardNTC SensorWiring harnessMain 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 Ideal 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