F3
FAULT CODE
Viessmann
Flame Signal Lost During Operation
High Severity
Engineer Required
The flame was detected but has been lost during normal operation. This may be caused by gas supply interruption or wind effects.
Step-by-Step Fix Guide
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Step 1
Check for external flue blockages
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Step 2
Verify gas supply is not interrupted
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Step 3 Engineer only
If recurring, a Gas Safe engineer should check the ionisation electrode and gas valve
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.