High Lockout
F.49 on Vaillant ecoTEC Plus 625

Your boiler has lost its ability to communicate with its external controls, such as your thermostat, due to an electrical glitch in the internal data wiring.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

eBUS under voltage. Short circuit on eBUS, overload on eBUS or two power sources on eBUS with different polarity

What causes this fault?

This fault occurs when there is an electrical conflict or a short circuit on the communication wires that link your boiler to your thermostat. The most common reason is a hardware failure in the external control receiver or a wiring fault that is preventing the internal computer from sending and receiving data correctly.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
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Related fault codes

F.22View →F.70View →

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