62 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 |
|---|---|---|
| 41-694-22 | ecoTEC plus 618 VU 186/5-5 (H-GB) R6 | 2017–present |
| 41-694-23 | ecoTEC plus 618 VU 186/5-5 (P-GB) R6 | 2017–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
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Your boiler has stopped working because it cannot communicate with the sensor that monitors the temperature of the water leaving the unit.
Your boiler has stopped working because it cannot accurately measure the temperature of the water returning to the unit.
Your boiler has temporarily stopped working because it has lost the signal from the sensor that monitors your hot water cylinder temperature.
Your boiler has lost the connection to the temperature sensor in your hot water storage cylinder, meaning it cannot properly monitor how hot the stored water is.
Your boiler has detected an electrical fault with the internal sensor that monitors the water temperature leaving the unit, causing it to shut down for safety.
Your boiler has stopped working because it thinks the water returning to the unit is much hotter than it actually is, causing it to shut down for safety.
Your boiler has lost the ability to measure the temperature of your hot water cylinder because of a faulty sensor or a wiring issue, meaning it cannot heat your water correctly.
Your boiler has detected an electrical fault with the sensor that monitors your hot water tank, meaning it cannot accurately tell if your water is hot enough.
Your boiler has switched itself off because it has reached an unsafe temperature and needs to cool down.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Your boiler has shut down because there is a significant difference between the water temperature leaving the boiler and the temperature returning to it, usually caused by a circulation problem.
Your boiler has shut down because the internal water temperature is heating up much faster than it can be circulated away, usually meaning the water is stuck or the pump is struggling.
Your boiler has shut itself down because the air being pushed out of the chimney pipe has become dangerously hot.
Your boiler has detected an issue with the valve that controls the flow of gas, meaning it cannot safely ignite or maintain a flame.
Your boiler has sensed a flame when there shouldn't be one, so it has shut down as a safety precaution to prevent damage.
Your boiler is trying to light itself to provide heat, but it is failing to create a flame, likely because it is not getting enough gas or the spark isn't catching.
Your boiler was working but the flame went out and it cannot manage to light itself back up.
Your boiler's fan is unable to spin at the correct speed, which prevents the boiler from safely clearing exhaust fumes and starting the ignition process.
Your boiler has detected an internal communication or configuration error with its main control board.
Your boiler has lost its ability to communicate with its external controls, such as your thermostat, due to an electrical glitch in the internal data wiring.
Your boiler has lost its connection to an internal sensor that measures the flow of air and gas, so it has safely shut down to prevent damage.
Your boiler has detected an unexpected flow of gas through its internal control valve, meaning it cannot safely regulate the fuel supply to start or keep the flame burning.
Your boiler is failing to start up properly because it is not receiving enough gas to ignite.
Your boiler has detected a fault with its built-in carbon monoxide monitoring sensor and has safely shut down to protect your home.
Your boiler has detected high levels of carbon monoxide and has automatically locked itself out for safety.
Your boiler is currently running a specialized internal testing program, usually activated by an engineer during setup or servicing, rather than indicating a standard breakdown.
Your boiler is unable to correctly control the flow of gas, causing it to shut down for safety purposes.
Your boiler has detected that the gas valve is not closing as quickly as it should, preventing the unit from shutting down the burner safely.
Your boiler's internal computer brain is having trouble reading its memory, causing the system to stop working for safety.
Your boiler has detected an internal communication error between its electrical sensors and the main control board, causing it to shut down for safety.
Your boiler's internal control board has become too hot and has shut down the system to prevent damage.
Your boiler's electronic control board has detected a confusing signal from the flame sensor, causing the system to shut down for safety.
Your boiler is struggling to keep its flame burning steadily, causing it to shut down for safety.
Your boiler’s control board has lost its identity settings, meaning the internal computer no longer knows which specific model it is supposed to be operating.
Your boiler is struggling to accurately measure the water temperature leaving the unit, usually because a sensor has failed or become disconnected.
Your boiler has detected that the sensors measuring water temperature going in and out are giving conflicting readings, so it has shut down as a safety precaution.
Your boiler is struggling to read how much water is in the system because of a sensor issue, which has caused it to stop working for your safety.
Your boiler's internal sensor has detected that the water pressure is too high or the sensor itself is sending an incorrect reading.
Your boiler is unable to sense water moving or pressure building when it tries to start up, which has caused it to shut down for safety.
Your boiler is struggling to push waste gases out through the flue or is unable to clear internal condensation water properly.
Your boiler is having trouble communicating with an external hot water control component, meaning it doesn't know the temperature of the water heading to your taps.
Your boiler is receiving an incorrect signal from the hot water storage cylinder sensor, which can temporarily disrupt your hot water supply.
Your boiler is having trouble moving hot water to your hot water cylinder, which means you might not have any hot water available.
Your boiler has detected an issue with its internal powered titanium anode protection system, which prevents corrosion inside the hot water cylinder.
Your boiler is firing up, but it doesn't detect the water getting hotter quickly enough, so it has shut down to prevent itself from overheating.
Your boiler is confused because its internal thermometers are giving conflicting readings and don't agree on how hot the water actually is.
Your boiler has stopped working because its internal thermometers are giving conflicting readings and believe they have been fitted to the wrong pipes.
Your boiler's main computer is having trouble communicating with its internal parts, meaning it has temporarily stopped working for safety.
Your boiler has lost the ability to monitor the water temperature in your hot water cylinder due to an electrical connection fault.
Your boiler's internal computer is receiving the wrong information about its own identity, preventing it from running safely.
Your boiler has detected that the fuel and air mixture inside is incorrect, meaning it cannot burn gas safely and efficiently.
Your boiler has detected an issue with the water flow and pressure sensors, which usually stops it from operating safely.
Your boiler is currently on standby because your thermostat or timer is not asking for any heating or hot water.
Your boiler is temporarily running at a lower power level to prevent a fault and ensure it can still provide some warmth while it detects a minor issue.
Your boiler is temporarily pausing its operation as part of a routine diagnostic testing programme.
Your boiler has temporarily limited its maximum heating power to protect itself, but it should still be operating normally.
Your boiler has detected a mismatch between the type of gas it is set up to burn and the electronic configuration on its main computer board.
Your boiler is currently running a calibration routine to check and adjust the combustion gases to ensure it burns efficiently and safely.
Your boiler has detected an issue with the gas supply route and has temporarily locked out for your safety.
Your boiler is reminding you that the internal water pressure has dropped and needs to be topped up.
Your boiler is currently running an automated self-test to check the flow and circulation of water inside the system.
Your boiler is temporarily blocking certain operations because it cannot correctly test or measure its exhaust gases at this moment.
Not faults — these are normal operating states. Tap to expand.
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BoilerFaultCodes