BoilerFaultCodesThe 6 most common faults
01
F.22 High DIY-safe
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
What to try first
Locate the two small taps or the flexible silver filling loop positioned underneath your boiler.Slowly open the valves to let water into the system until the pressure gauge on the front display shows between 1.0 and 1.5 bar.Ensure both valves are tightened firmly shut again to prevent the pressure from rising too high.
02
F75 High Engineer
Your boiler is struggling to detect water moving through the system properly, which is preventing it from safely starting up.
Full guide for F7503
F.75 High Engineer
Your boiler is not detecting the necessary water movement to heat your home, which is likely caused by a blocked pump or a faulty pressure sensor.
Full guide for F.7504
F.00 High Engineer
Your boiler has lost the signal from the sensor that monitors the water temperature, causing it to stop heating your home as a safety precaution.
Full guide for F.0005
F.01 High Engineer
Your boiler has lost its connection to a sensor that measures the water returning to the system, causing it to stop heating as a safety precaution.
Full guide for F.0106
F.10 High Engineer
Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside the unit due to a faulty electrical sensor connection.
Full guide for F.10on the Vaillant ecoTEC Plus 826
Filling loopPressure relief valvePressure sensorCentral heating pumpExpansion vesselFlow 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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