BoilerFaultCodesThe 6 most common faults
01
A04 High DIY-safe
Your boiler has stopped because the water pressure inside the heating system has dropped too low to operate safely.
What to try first
Locate the external filling loop, which is usually a small silver braided hose with one or two valves located underneath your boiler.Gradually open the valve(s) to allow mains water into the system while watching the pressure gauge on the front of the boiler.Close the valve(s) tightly once the needle on the gauge reaches the green zone, typically between 1.0 and 1.5 bar.
02
A01 High Engineer
Your boiler is failing to light because it cannot detect a flame, meaning you currently have no heating or hot water.
Full guide for A0103
A02 High Engineer
Your boiler has detected that it is running too hot and has automatically shut down to prevent internal damage.
Full guide for A0204
A03 High Engineer
Your boiler's air circulation system isn't sending a signal back to the main controller, so the unit has safely shut down to prevent improper combustion.
Full guide for A0305
A06 High Engineer
Your boiler’s internal computer chip has lost the connection to its pre-set configuration settings, meaning it doesn't know how to operate correctly.
Full guide for A0606
A07 High Engineer
Your boiler has detected that the water temperature is too hot or the sensor measuring it is broken, so it has shut down to prevent damage.
Full guide for A07on the Vokera Mynute i
Pressure Relief ValvePressure GaugeExpansion VesselIgnition electrodeGas valvePCB
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 Vokera 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