F.26
FAULT CODE
Vaillant
Gas Valve Error
High Severity
Engineer Required
The gas valve has a fault and may not be functioning correctly. This is a safety-critical component that controls the gas supply to the burner.
Step-by-Step Fix Guide
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Step 1
Do not attempt to fix gas valve faults yourself
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Step 2
Turn off the boiler
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Step 3 Engineer only
Call a Gas Safe registered engineer immediately
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.