The Alpha E37 fault code generally means that the boiler has detected an insufficient electrical supply voltage. On Alpha boiler ranges that use code 37, the fault description is “low supply voltage”, meaning the boiler does not have enough electrical supply to operate correctly. This is not usually a water-pressure, gas-supply or radiator-circulation fault. However,…
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If you have searched for the Alpha E01 fault code, your Alpha E-Tec 28 or E-Tec 33 boiler may show the fault as 01 on its display. On these models, code 01 means an ignition failure: the boiler attempted to light but did not detect a flame during the ignition sequence. It can be linked…
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If your Alpha boiler is displaying the E10 fault code, it normally means the central-heating system pressure is too low for the boiler to operate correctly. On Alpha E-Tec NX 28 and 33 models, E10 is described as primary system pressure low. On E-Tec Plus NX 28, 33 and 38 models, it is described as…
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Vitodens 100 fault codes help identify why a Viessmann boiler has stopped, locked out or is not operating correctly. The code may point to an ignition problem, low water flow, overheating, a temperature sensor, fan issue or boiler-control fault. This guide focuses mainly on common Vitodens 100-W fault-code displays. However, Viessmann fault codes can vary…
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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 Worcester Bosch boiler is showing U9, it may not be a conventional fault code. On certain older Worcester Bosch Greenstar CDi boilers with a two-character display, U0 to U9 represent temperatures from 100°C to 109°C. This means U9 shows that the boiler flow temperature has reached 109°C. A U9 display does not identify…
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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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