A Viessmann F5 fault code on an older Vitodens 100-W boiler usually relates to the boiler’s air-pressure and flue safety checks. The boiler may lock out when it cannot confirm the correct conditions for safe operation. This guide is for older Vitodens 100-W boilers only. Viessmann fault-code meanings can differ between boiler models, so always…
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If your boiler is showing a Viessmann FD fault code, this guide is for the older Viessmann Vitodens 100-W B1HC and B1KC range. On these boilers, FD means the burner has been blocked because the boiler has detected a possible burner control unit fault. It is not simply a generic ignition or flame-detection code. The…
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If your Viessmann Vitodens 100-W boiler is showing the F1 fault code, it has locked out because the maximum flue gas temperature has been exceeded. On Vitodens 100-W models using this fault-code format, Viessmann’s service information directs engineers to check the heating-system fill level, circulation pump and whether the system needs bleeding. The F1 code…
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If your Viessmann Vitodens 100-W boiler is showing an FF fault code, the boiler has entered a safety lockout and needs attention. On Vitodens 100-W models that use this fault-code format, FF usually means the burner has been blocked because the boiler has detected a fault in the burner control circuit. This can involve the…
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The Viessmann F2 fault code usually means the boiler has gone into a safety lockout because it has detected an overheating or temperature-limiter issue. On many Viessmann Vitodens boilers, this can be linked to poor water circulation, trapped air, low system pressure, a pump problem, or a fault with the temperature limiter itself. The exact…
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The Viessmann F4 fault code commonly appears when a boiler cannot confirm that a burner flame has been established and enters a safety lockout. On several Vitodens models, F4 is listed as a “no flame signal” fault. However, Viessmann says fault-code meanings can vary by boiler model, and on some Vitodens gas boilers an F4…
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