F.42
FAULT CODE
Vaillant
Coding Resistor / Gas Valve Fault
High Severity
Engineer Required
The coding resistor for the gas valve is giving an incorrect signal, or the gas valve itself has developed a fault.
Step-by-Step Fix Guide
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Step 1
Do not attempt to repair this yourself
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Step 2
A Gas Safe engineer will need to check the gas valve wiring and coding resistor
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Step 3 Engineer only
The gas valve or PCB may need replacing
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.