BoilerFaultCodesThe 6 most common faults
01
HIGH High DIY-safe
Your boiler has too much water inside the system, causing the pressure to rise above the safe limit.
What to try first
Locate a radiator anywhere in your house.Open the bleed valve on the radiator using a radiator key to let water out.Place a container underneath to catch the water and watch the boiler pressure gauge.Close the valve once the pressure drops into the green zone (usually around 1.5 bar).
02
Block 01 High Engineer
Your boiler has been automatically shut down because an external safety device, such as a frost thermostat or a heat link, has triggered a signal to stop the system.
Full guide for Block 0103
Block 80 High Engineer
Your boiler has automatically stopped heating because the exhaust gases getting rid of your smoke and fumes are currently too hot.
Full guide for Block 8004
Block 81 High Engineer
Your boiler has stopped working because it cannot detect a vital safety sensor that monitors the temperature of the gases leaving your home.
Full guide for Block 8105
Block 82 High Engineer
Your boiler has detected an electrical fault in a sensor that monitors exhaust gases and has safely shut down to prevent incorrect operation.
Full guide for Block 8206
Block 85 High Engineer
Your boiler is currently running a self-cleaning air-removal cycle because it cannot detect water moving through the system properly.
Full guide for Block 85on the Atag Q 30CR
Pressure relief valvePressure sensor/transducerExternal frost statExternal controls interfaceWiring connectionFlue gas sensor
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 Atag 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