F.19
FAULT CODE
Vaillant
eBUS Subscriber Voltage Too High
Medium Severity
Engineer Required
The voltage on the eBUS data communication line is higher than expected, often caused by a wiring fault or incompatible third-party device.
Step-by-Step Fix Guide
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Step 1
Check all wiring to thermostats and external controls
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Step 2
Disconnect any recently added third-party controls and reset
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Step 3 Engineer only
Call a Gas Safe engineer if the fault persists
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.