Vokèra · Vision, Compact A and Unica A-code platform
A77Low-temperature thermostat fault
This code applies to Vision 25C, Vision 30C, Compact A, Unica 28i, Unica 32i. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Do not remove the boiler case.
- Record the full code and model, then arrange a Gas Safe registered engineer.
How an engineer may fix it
Follow the model-specific fault-finding procedure, test the indicated circuit or component, repair the cause and recommission the appliance.
Some status codes apply only to certain variants. Confirm the exact user manual.
Manufacturer source: Vokèra — Vision Combi 25C/30C User, Installation and Servicing Manual. Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.