BoilerFaultCodesThe 6 most common faults
01
F.22 High DIY-safe
Your boiler has detected that the water pressure inside the system has dropped too low to operate safely.
What to try first
Locate the filling loop (a silver flexible hose or internal lever) under the boiler.Open the valve(s) slowly to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) tightly to stop the flow.
02
F.00 High Engineer
Your boiler is unable to measure the temperature of the water inside it, so it has safely shut down to prevent overheating.
Full guide for F.0003
F.01 High Engineer
Your boiler is struggling to accurately measure the temperature of the water returning to it, so it has stopped working to prevent potential overheating.
Full guide for F.0104
F.10 High Engineer
Your boiler has stopped working because it is unable to accurately measure the temperature of the water flowing through the system due to a faulty electrical connection or sensor.
Full guide for F.1005
F.11 High Engineer
Your boiler has stopped working because it is unable to accurately read the temperature of the water returning to it, causing it to shut down for safety.
Full guide for F.1106
F.91 High Engineer
Your boiler is struggling to detect the temperature of your hot water cylinder because there is an electrical connection issue with the sensor.
Full guide for F.91on the Glow-worm Energy2 30c
Pressure relief valveExpansion vesselPressure sensorNTC Temperature SensorWiring harnessReturn temperature 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 Glow-worm 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
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