28 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
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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 |
|---|---|---|
| 47-364-61 | UNICA MAX 35C | 2021–present |
| 47-364-62 | UNICA MAX 40C | 2021–present |
| 47-364-75 | UNICA MAX 30C | 2022–present |
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Your boiler has lost the digital connection between its main control board and the display or smart system, meaning it cannot receive the instructions it needs to run.
Your boiler has failed to light the gas burner or stay lit, causing it to shut down for safety.
Your boiler detects a flame when there shouldn't be one, which is a safety mechanism that stops the unit from operating.
Your boiler has shut down because it has detected it is getting too hot, triggering a safety switch to prevent damage.
Your boiler has failed to detect a flame or is having trouble monitoring the burner, causing it to shut down for safety.
Your boiler is having trouble detecting the flame it needs to stay lit, causing the system to shut down for safety.
Your boiler is struggling to detect the flame needed to heat your home, causing it to shut down for safety.
The boiler has detected a problem with the flame sensor that keeps the gas burner running safely, causing the system to shut down.
Your boiler has stopped working because the internal fan, which safely exhausts fumes, is not spinning at the correct speed or has failed to start.
Your boiler has detected that the water pressure is either too low or too high, or the sensor that measures it is not working correctly.
Your boiler has detected that the water pressure is too low for it to operate safely, though it may currently be treating this as a temporary issue.
Your boiler is struggling to monitor water pressure correctly due to a sensor issue, which has caused it to stop working for safety.
Your boiler has detected an issue with the electrical power supply coming into the unit, which is preventing it from running safely.
Your boiler's temperature sensor for hot water has stopped working correctly, meaning your taps and showers may not get warm.
Your boiler is having trouble controlling its internal power level and burner intensity, which prevents it from heating properly.
The boiler's flame detection system has failed to safely prove that the burner is lit, causing the unit to shut down for safety.
Your boiler has detected that the water is getting too hot or isn't flowing correctly through the system, causing it to shut down for safety.
Your boiler has detected an issue with the sensor that monitors the temperature of the water in your main heating circuit, which may prevent your radiators from warming up correctly.
Your boiler has detected that the water returning from your radiators is too hot or the temperature sensor itself has developed a fault, causing the system to shut down for protection.
Your boiler has detected high levels of carbon monoxide or improper combustion and has shut down as a safety precaution.
Your boiler has detected a blockage in the flue pipe or an issue with how exhaust gases are being cleared, causing it to shut down for safety.
The boiler's safety system is struggling to detect a stable flame, meaning it cannot stay on safely to provide heating and hot water.
Your boiler has detected that the exhaust gases are getting too hot or the sensor that monitors them has failed, causing the system to shut down for safety.
Your boiler has detected that the main heating component is becoming blocked or dirty, which is preventing it from transferring heat efficiently.
Your boiler has detected an unsafe level of carbon monoxide or poor combustion and has shut down as a safety precaution.
Your boiler has detected an unsafe level of carbon monoxide or improper burning of gas and has shut down as a safety precaution.
Your boiler has detected a problem with the flame or the sensor that monitors it, causing the system to shut down for safety.
Your boiler has been manually reset too many times in a short period and has locked itself for safety to prevent further damage.
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BoilerFaultCodes