What the manual says
Manufacturer manualFault code 05 appears if the appliance is connected to the optional remote control (RC05) and there is a communication problem.
From this model's manual
Verified against the Vokera/Vokera Synergy_installation_and_servicing_instructions installation & service manual.
DIY fix possible
Locate the remote control unit and check that it has fresh batteries.Turn the boiler off at the mains power switch for 60 seconds to reset the connection.Check the wiring connections behind your thermostat to ensure no wires have come loose.
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Related fault codes
All 11 fault codes on the Synergy
Seeing a different code? Every code this model can display, in one place.