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F.49

eBUS voltage too low

The boiler has detected an eBUS communication voltage fault.

What this code means

The boiler has detected an eBUS communication voltage fault.

Possible causes

  • Short circuit on eBUS
  • Excessive eBUS load
  • Two power supplies connected with different polarity

Common symptoms

  • F.49 displayed
  • Controls or connected devices may stop communicating

Checks to make

  1. Do not alter internal bus wiring unless qualified
  2. Arrange check of eBUS wiring and connected controls

Safety

  • Do not remove the boiler casing or work on gas, combustion, flue or internal electrical components unless appropriately qualified. If gas is suspected, follow the national gas-emergency procedure.

Model notes

Vaillant notes that not every fault code is visible on every product model.