9 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 41-019-09 | Ultrapower 100 SXI | 2007–present |
| 41-019-10 | Ultrapower 170 SXI | 2007–present |
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Your boiler has detected that it is running too hot and has automatically shut down to prevent damage to its internal parts.
Your boiler has detected an issue with the internal fan that pushes exhaust gases out of your home, so it has safely shut down to prevent unsafe operation.
Your boiler is successfully igniting but is unable to keep the flame burning, causing it to shut down shortly after starting.
Your boiler is struggling to accurately measure the temperature of the hot water because the sensor responsible for this information has a loose or broken connection.
Your boiler has lost the electrical connection to a sensor that measures the temperature of the water returning to it, so it has shut down as a precaution.
Your boiler's computer memory has encountered an internal error and can no longer process instructions correctly, meaning the unit will not start.
Your boiler has detected an issue with the valve that regulates the fuel supply, meaning it cannot safely ignite or maintain a flame.
Your boiler is having trouble communicating with its internal controls or the thermostat, meaning it cannot receive the signal to start heating your home or water.
Your boiler has failed to light the flame needed to provide heating or hot water, and it has now locked itself out for safety.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes