What are the Common Faults with Vaillant Ecotec Boilers? While the Vaillant ecoTEC Plus (including the 831, 838 combi, and 637 system models) remains a reliable, high-efficiency boiler, component wear and system issues inevitably trigger digital fault codes. Safe resolution depends on the root cause: external pressure drops can often be checked by homeowners, but … Continue reading Common Faults on the Vaillant ecoTEC Plus