Vaillant ecoTEC plus 940 VUI 30/40CS/1-5 Fault codes & diagnostics

Your boiler has detected an internal electrical power supply failure on its main control board.

Your boiler has lost its connection to a temperature probe, meaning it cannot tell how hot the water is and has stopped working for your safety.

Your boiler has lost its connection to the sensor that measures how hot the water is as it flows back into the unit, forcing it to shut down for safety.

Your boiler has lost the connection to the sensor that measures the temperature of your hot water, so it cannot currently provide hot water to your taps or shower.

Your boiler has detected a faulty signal from a heat sensor, causing it to stop heating your home as a safety precaution.

Your boiler has detected an electrical fault in a sensor that measures the temperature of water returning to the unit, causing it to stop working for safety reasons.

Your boiler has automatically shut down because it reached a dangerously high temperature to prevent damage to the internal components.

Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low to operate safely.

Your boiler has detected that the water leaving it is much hotter than the water returning, suggesting a blockage or a problem with the pump circulating the water efficiently.

Your boiler is shutting down because the water inside it is heating up much faster than it can be moved around your radiators, suggesting a flow issue.

Your boiler has detected that the exhaust gases leaving the unit are hotter than they should be, so it has shut down to protect itself from overheating.

Your boiler has stopped working because the pipe that drains away waste water is blocked, which is often caused by frozen water in cold weather.

Your boiler has temporarily stopped working because the pipe that drains away waste water is likely blocked or frozen.

Your boiler is struggling to breathe properly because the internal fan that pushes air out is not spinning at the correct speed.

Your boiler is struggling to get the right balance of air for a clean burn, which prevents it from igniting safely.

Your boiler has lost the digital instructions telling it how to configure itself for your specific heating system, preventing it from starting up safely.

Your boiler is struggling to detect the flame needed to heat your water and home, so it has shut down to stay safe.

Your boiler's communication wires are experiencing a wiring conflict or short circuit, which is preventing the system from sending signals correctly.

Your boiler has detected a critical issue with its internal combustion control system that it cannot fix itself, so it has shut down for your safety.

Your boiler's internal computer is failing to start up or communicate correctly, which has caused the system to shut down for safety.

Your boiler is struggling to confirm that the flame has turned off as quickly as it should have, which means it has stopped working for safety reasons.

Your boiler's computer is struggling to store or read its internal settings properly, which prevents it from starting up safely.

Your boiler has detected an internal electronic reading error, meaning it cannot safely process vital temperature measurements.

Your boiler has detected that one of its internal electronic parts is running far too hot and has shut itself down to prevent damage.

Your boiler is unable to safely detect whether the burner flame is lit, so it has shut itself down to prevent a safety hazard.

Your boiler is struggling to detect the flame reliably, so it has turned itself off to stay safe, meaning you currently have no heating or hot water.

Your boiler’s internal computer is confused because it cannot correctly identify the specific hardware model it is currently installed in.

Your boiler's internal thermometer is sending conflicting temperature readings to the control board, so the system has shut down to prevent damage.

Your boiler is struggling because it cannot detect a normal temperature difference between the water leaving and returning to the unit, suggesting the system is not circulating heat correctly.

Your boiler is struggling to detect the movement of water when it tries to start the heating, which usually means the internal pump is failing to spin or there is a blockage preventing flow.

Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage to its internal parts.

Your boiler has detected an issue with the drainage system or flue safety mechanism, so it has safely stopped working to prevent potential water damage or combustion faults.

Your boiler's electronic brain is having trouble communicating with an external control accessory, preventing the system from operating correctly.

Your boiler is struggling to pump hot water into your hot water cylinder, which means you may have no hot water available.

Your boiler is failing to heat up the water properly when it tries to start, so it has shut itself down to prevent damage.

Your boiler is confused because it detects a strange temperature difference between the water leaving the boiler and the water coming back, causing it to shut down to protect itself.

Your boiler's temperature sensors have been fitted incorrectly or have become misaligned, preventing the system from accurately reading the water temperature.

Your boiler has lost the internal electrical connection needed to spark and light the burner, meaning it cannot produce any heat or hot water.

Your boiler has lost the internal connection needed to control the gas supply, which prevents it from igniting and heating your home.

Your boiler has detected that the internal water pump is not the correct version required for this specific model, preventing the system from circulating heat properly.

Your boiler has lost its digital connection to the hot water cylinder, meaning it currently doesn't know how to heat your stored water.

Your boiler has detected that the settings controlling how it uses gas were not finalized correctly during its last setup or maintenance, which prevents it from firing up safely.

Your boiler is having trouble managing its internal gas flow, which is preventing it from firing up reliably.

Your boiler has detected that a small internal component responsible for regulating the gas flow is stuck or worn out, which prevents it from safely igniting.

Your boiler's internal computer has flagged a self-test failure, meaning it cannot safely control its operations and will remain shut down to prevent damage.

Your boiler requires a special electronic calibration procedure following the replacement of key internal parts before it can safely fire up again.

Your boiler's internal electronic control center is failing to receive a consistent power signal, which is preventing the system from operating safely.

Your boiler has detected that the incoming electricity supply is too weak to run the system safely.

Your boiler is having trouble directing water properly between your radiators and your taps because a motorised valve isn't moving.

Your boiler has temporarily stopped working because the internal water pump is jammed and cannot clear itself.

Your boiler's water pump has encountered an internal communication error, meaning it cannot circulate heat to your radiators or taps.

Your boiler’s internal water pump has become too hot and the system can no longer safely circulate heat, causing the boiler to shut down to prevent damage.

Your boiler has detected that the water pump inside is spinning without being fully submerged in water, preventing it from circulating heat around your home.

Your boiler has lost the electrical connection needed to keep its internal water pump running, so it has safely shut down to prevent overheating.

Your boiler has detected that the water pump responsible for circulating heat to your radiators and taps has stopped working correctly.

Your boiler has detected that multiple internal water-control parts are failing to respond properly, which usually shuts down the system to prevent damage.

Your boiler's water circulation pump is failing to start as expected, which means the system cannot safely move heat to your radiators or taps.

Your boiler is failing to start because it cannot detect the correct setup of its exhaust pipe system.

Your boiler has identified that its internal settings do not match the physical components installed, which usually happens after a recent repair or incorrect parameter configuration.

Your boiler has detected that the flue system installed is incompatible with its internal setup, meaning it cannot safely vent exhaust gases.

Your boiler has detected that the settings controlling its flue system do not match the physical installation, preventing it from operating safely.

Your boiler is struggling to bring in the right amount of air needed to burn fuel correctly, so it has safely shut down to prevent any issues.

Your boiler's air-flow sensor is failing to provide a consistent reading, preventing the unit from safely igniting.

Your boiler has detected an internal communication error and has safely shut down because it cannot accurately monitor or control the burner process.

Your boiler has temporarily stopped working because moisture has been detected inside the wrong part of the machine.

Your boiler's computer is having trouble saving or reading its internal memory settings, which prevents it from operating correctly.

Your boiler's control panel and its internal computer are failing to talk to each other, which prevents the system from starting.

Your boiler has lost internal communication with one of its main control parts, meaning it cannot properly coordinate heating and hot water.

Your boiler has shut down because the flame went out unexpectedly while it was running at its lowest setting.

Your boiler has detected that there is not enough water circulating through your heating system to work properly.

Your boiler is struggling to accurately measure the speed of the water circulating inside it, which will prevent your heating and hot water from working correctly.

Your boiler is struggling to control its gas flow properly, meaning it cannot maintain a stable flame to heat your water or home.

Your boiler's gas control mechanism has reached its operational adjustment limit, meaning it can no longer properly balance the fuel and air mix to heat your home safely.

Your boiler is struggling to mix the right amount of air with the gas it uses to create a flame, which means it has safely shut itself down to prevent inefficient burning.

Your boiler has failed to remove air from its internal system during the start-up process, meaning it cannot begin heating your water safely.

Your boiler is struggling to detect the flame correctly, so it has turned itself off to stay safe and prevent gas from building up.

Your boiler has detected an internal electrical fault within its control system, which is preventing it from starting up correctly.

Your boiler is receiving insufficient power from your home's electrical supply, which is preventing it from operating correctly.

Your boiler has detected that the incoming electricity supply is at a dangerously high voltage, so it has shut itself down to protect its internal electronics from being permanently fried.

Your boiler is struggling to push water around your heating system because a path that allows internal water flow has become restricted or blocked.

Your boiler's water pump is stuck, so the system is trying to clear the obstruction automatically before it stops working entirely.

Your boiler has detected that the internal water pump component is getting too hot, so it has safely shut down to prevent further damage.

Your boiler is struggling to accurately measure the airflow needed for safe combustion, so it has safely shut down to prevent incorrect operation.

Your boiler's internal sensor that detects how much water is inside is currently sending a confusing signal, so the system has stopped working to stay safe.

Your boiler is struggling to accurately measure the water flowing through it, which is preventing it from heating your water safely.

Your boiler has detected that the internal water pump is not the correct type for your specific model, preventing the system from circulating water properly.

Your boiler is having trouble controlling the flow of gas accurately, which means it cannot safely or efficiently ignite, resulting in a loss of heating and hot water.

Your boiler's gas control mechanism is struggling to function correctly, preventing the unit from igniting or maintaining a steady flame.

Your boiler is struggling to mix the right amount of air with its gas supply to burn fuel efficiently.

Your boiler is struggling to detect the flame needed to heat your home, and it has tried and failed to adjust itself automatically.

Your boiler's internal computer is failing to receive a stable electrical supply, which means the unit cannot start or operate.

Your boiler has detected that hot water is not transferring correctly through its internal heating system, so it is limiting its own performance to prevent further stress.

Your boiler has lost the internal connection to the water pump, meaning it is currently unable to circulate heat to your radiators or taps.

Your boiler is currently running diagnostic checks to determine why it is struggling to safely light and maintain a flame.

Your boiler has detected an issue with the internal water pump that circulates heat through your home.

Your boiler is having trouble directing water between your radiators and your taps because the valve responsible for switching between them is not moving correctly.

Your boiler has detected an issue with the internal fan that safely pushes waste gases out of your home, so it has temporarily stopped working to keep you safe.

Your boiler is having trouble moving hot water to your cylinder to heat your taps and showers.

Your boiler has detected an issue with the internal water pump, which means it cannot properly circulate water around your home for heating and hot water.

Your boiler is not detecting the external water pump properly, which usually stops your heating and hot water from working.