F49
FAULT CODE
Glow-worm
eBUS Communication Fault
Medium Severity
Engineer Required
Communication failure between the boiler and a connected Vaillant Group controller (sensoCOMFORT, sensoHOME, MiGo etc.) over the eBUS data bus.
Step-by-Step Fix Guide
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Step 1
Check that all wiring connections to the thermostat/controller are secure
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Step 2
Turn the boiler off at the mains for 10 minutes, then restart
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Step 3 Engineer only
If fault persists, call a Gas Safe engineer to test the eBUS wiring
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.