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Michael FergusonAug 30, 2025
How to resolve fault code C7 on a Viessmann B2TB004 Boiler?
- Wwayne71Aug 31, 2025
If your Viessmann Boiler displays fault code C7, it indicates a communication error with the external variable speed heating circuit pump, heating circuit 1 (without mixer). Check setting of coding address "E5".











