BoilerFaultCodesThe 6 most common faults
01
1 High Engineer
Your boiler has temporarily stopped working because it either got too hot or detected a faulty temperature sensor.
Full guide for 102
2 High Engineer
Your boiler has automatically shut down because it has detected an unusually high temperature inside the system.
Full guide for 203
3 High Engineer
Your boiler is trying to start up or keep running, but the flame keeps going out.
Full guide for 304
4 High Engineer
Your boiler has stopped working because it cannot safely detect airflow through the flue or has lost internal communication.
Full guide for 405
5 High Engineer
Your boiler has lost its memory or programming settings, meaning it cannot safely control your heating.
Full guide for 506
6 Medium Engineer
Your boiler is experiencing an unspecified general error indicated by flashing indicator lights, which requires a professional inspection to diagnose safely.
Full guide for 6on the Potterton Ultra 24 Heat
NTC Temperature SensorOverheat ThermostatPrinted Circuit Board (PCB)High limit thermostatPUMPPCB
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
Boiler cover options
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Approved partner
Get a quote →
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Affiliate links. We may earn a commission at no extra cost to you.