BoilerFaultCodesThe 6 most common faults
01
E01-840 High DIY-safe
Your boiler has lost water pressure, and the internal component used to refill it is likely disconnected or faulty.
What to try first
Locate the internal filling link (white key or lever) at the bottom of the boilerEnsure the key is pushed in fully and turned to the locked positionTurn the grey square knob to top up the pressure until the needle is between 1 and 1.5 bar
02
E00-730 High Engineer
Your boiler is not detecting the correct airflow needed to operate safely, so it has shut itself down to prevent any issues.
Full guide for E00-73003
E80-450 High Engineer
Your boiler is unable to regulate the gas supply correctly, which is preventing it from firing up to provide your heating and hot water.
Full guide for E80-45004
E00-720 High Engineer
Your boiler is failing to ignite the flame needed to produce heat and hot water.
Full guide for E00-72005
E01 612 High Engineer
Your boiler has temporarily stopped working because it cannot safely detect the burner flame.
Full guide for E01 61206
E00-711 High Engineer
Your boiler is struggling to transfer heat between its internal systems, which means it cannot reliably provide hot water or heating.
Full guide for E00-711on the Worcester Bosch CDi RSF
Internal Filling KeyFilling Link AssemblyFlow TurbineAir pressure switchFan assemblyVenturi/tubing
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 Worcester Bosch 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