BoilerFaultCodesThe 6 most common faults
01
F.22 High DIY-safe
Your boiler has stopped working because it does not have enough water inside the system to run safely.
What to try first
Locate the external filling loop, which is a silver braided hose connecting two pipes underneath your boiler.Open the valves at both ends of the filling loop to let water enter the system.Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches 1.5 bar.Restart your boiler so it can continue its normal operation.
02
F.00 High Engineer
Your boiler has stopped working because it has lost the connection to the sensor that measures the temperature of the water inside the system.
Full guide for F.0003
F.01 High Engineer
Your boiler has lost the signal from one of its internal temperature sensors, causing it to shut down for safety to prevent 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 inside it, triggering a safety shut-off.
Full guide for F.1005
F.11 High Engineer
Your boiler has detected a faulty connection to a sensor that measures the temperature of the water returning to the system, causing it to stop运行 as a safety precaution.
Full guide for F.1106
F.23 High Engineer
Your boiler has detected that the water inside it is heating up or moving much differently than it should, so it has shut itself down to prevent overheating.
Full guide for F.23on the Vaillant ecoFIT Pure 412
Filling loopPressure sensorExpansion vesselFlow 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 Vaillant 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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