BoilerFaultCodes D.22
Your boiler is currently performing an internal background system check and is not actually reporting a hardware malfunction.
Vaillant Turbomax Plus VUW 242EH Fault codes & diagnostics
59 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 24 kW 2000-2005 Discontinued
Replaced by: ecoMAX
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Severity at a glance
Each cell = one fault code. Hover to identify. 2 Emergency
29 High
2 Medium
26 Low
Just want the most common Vaillant Turbomax Plus VUW 242EH faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 59 documented codes
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D.24 Your boiler is currently performing a diagnostic check on its external controls, such as your room thermostat or timer, to ensure they are communicating correctly.
Your boiler is currently performing a diagnostic check on its external controls, such as your room thermostat or timer, to ensure they are communicating correctly.
Parts commonly replaced
- External thermostat
- Timeclock/Programmer
- PCB
Related codes
F 22 Your boiler has detected that the water pressure level inside the heating system has dropped too low to operate safely.
Your boiler has detected that the water pressure level inside the heating system has dropped too low to operate safely.
What to check first
- Locate the filling loop (a metal braided hose) underneath the boiler or near your pipes.
- Slowly open the valves on the filling loop to let mains water into the system until the pressure gauge on the front reads between 1.0 and 1.5 bar.
- Close both valves tightly to prevent over-pressurisation.
Parts commonly replaced
- Pressure relief valve
- Pressure sensor
- Expansion vessel
Related codes
F.00 Your boiler has lost connection with its internal temperature sensor, meaning it cannot monitor heat levels and has shut down as a safety precaution.
Your boiler has lost connection with its internal temperature sensor, meaning it cannot monitor heat levels and has shut down as a safety precaution.
Parts commonly replaced
- Flow NTC thermistor
- NTC wiring harness
- PCB
Related codes
F.01 Your boiler has stopped working because a sensor that monitors water temperature has lost its connection or stopped sending a signal.
Your boiler has stopped working because a sensor that monitors water temperature has lost its connection or stopped sending a signal.
Parts commonly replaced
- Flow NTC Thermistor
- Sensor Wiring Harness
Related codes
F.10 Your boiler has detected a loose connection or a fault with the sensor that monitors the temperature of the water returning to the unit.
Your boiler has detected a loose connection or a fault with the sensor that monitors the temperature of the water returning to the unit.
Parts commonly replaced
- NTC Return Sensor
- Wiring harness
- Main PCB
Related codes
F.11 Your boiler has detected a faulty electrical signal from the temperature sensor that monitors the water returning to the unit, meaning it cannot accurately judge when to heat your home.
Your boiler has detected a faulty electrical signal from the temperature sensor that monitors the water returning to the unit, meaning it cannot accurately judge when to heat your home.
Parts commonly replaced
- Return NTC thermistor
- Wiring harness
Related codes
F.13 Your boiler has detected an electrical short circuit in its internal temperature sensor, causing the system to shut down for safety.
Your boiler has detected an electrical short circuit in its internal temperature sensor, causing the system to shut down for safety.
Parts commonly replaced
- NTC Temperature Sensor
- Wiring Harness
- Main PCB
Related codes
F.20 Your boiler has switched itself off because it has become too hot internally and needs time to cool down before it can be used again.
Your boiler has switched itself off because it has become too hot internally and needs time to cool down before it can be used again.
What to check first
- Check that all radiator valves are fully open to allow water to flow.
- Wait 30 minutes for the unit to cool down completely.
- Press the reset button (indicated by a flame with a cross through it) on the front control panel.
Parts commonly replaced
- Overheat Thermostat
- Circulation Pump
- NTC Sensor
Related codes
F.22 Your boiler has detected that there is not enough water pressure in the system to operate safely, causing it to shut down to prevent overheating.
Your boiler has detected that there is not enough water pressure in the system to operate safely, causing it to shut down to prevent overheating.
What to check first
- Locate the silver braided filling loop hoses underneath or near the boiler.
- Open the two small valves on the filling loop to allow water into the system.
- Watch the pressure gauge on the front of the boiler until it reaches between 1.0 and 1.5 bar, then close both valves tightly.
Parts commonly replaced
- Filling loop
- Pressure sensor
- Expansion vessel
Related codes
Showing 11–20 of 59
F.23 Your boiler has detected that it is not circulating water properly, which stops the system from heating up to prevent internal damage.
Your boiler has detected that it is not circulating water properly, which stops the system from heating up to prevent internal damage.
Parts commonly replaced
- Circulation pump
- NTC sensors
- Pump wiring harness
Related codes
F.24 Your boiler is struggling to move water around the system, often because the water level is too low or something is blocking the flow.
Your boiler is struggling to move water around the system, often because the water level is too low or something is blocking the flow.
What to check first
- Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.
- If the pressure is low, use the filling loop valves underneath the boiler to top it up.
- Ensure all radiator valves are fully open to allow water to flow freely.
Parts commonly replaced
- Circulating pump
- Pressure sensor
- Heat exchanger
Related codes
F.27 Your boiler has detected an internal breakdown that is preventing it from starting up correctly, so it has shut itself down as a safety precaution.
Your boiler has detected an internal breakdown that is preventing it from starting up correctly, so it has shut itself down as a safety precaution.
Parts commonly replaced
- Main electronic PCB
- Gas valve
Related codes
F.28 Your boiler is trying to start up but cannot light the gas flame required to provide heat or hot water.
Your boiler is trying to start up but cannot light the gas flame required to provide heat or hot water.
What to check first
- Check that your gas emergency control valve is open and you have credit on your meter.
- Test another gas appliance, like a hob, to ensure gas is reaching the property.
- Press the 'Flame' or 'Reset' button on the boiler control panel for one second.
Parts commonly replaced
- Ignition Electrode
- Gas Valve
- Ignition Lead
- Spark Generator
Related codes
F.29 Your boiler was working but the flame has gone out unexpectedly, often due to an interrupted gas supply or a blockage in the drainage pipe.
Your boiler was working but the flame has gone out unexpectedly, often due to an interrupted gas supply or a blockage in the drainage pipe.
What to check first
- Check that your gas emergency control valve is open and you have credit on your meter.
- If it is freezing outside, check if the plastic condensate pipe leading outdoors is frozen and thaw it with warm water.
- Press the 'Flame/Cross' reset button for one second to see if the boiler restarts.
Parts commonly replaced
- Ignition electrodes
- Gas valve
- Flame sensing electrode
Related codes
F.32 Your boiler has detected an issue with the fan that helps it vent safely, so it has stopped working to protect itself.
Your boiler has detected an issue with the fan that helps it vent safely, so it has stopped working to protect itself.
Parts commonly replaced
- Fan
- Fan wiring harness
Related codes
F.33 Your boiler has stopped working because it cannot confirm that air is moving through the flue correctly, triggering a safety shut-down to prevent combustion issues.
Your boiler has stopped working because it cannot confirm that air is moving through the flue correctly, triggering a safety shut-down to prevent combustion issues.
Parts commonly replaced
- Air pressure switch
- Fan unit
- Venturi
- Printed Circuit Board
Related codes
F.37 Your boiler has detected that the fan, which manages the air and gas mixture, is not spinning at the correct speed, causing the system to stop working for safety reasons.
Your boiler has detected that the fan, which manages the air and gas mixture, is not spinning at the correct speed, causing the system to stop working for safety reasons.
Parts commonly replaced
- Air pressure switch
- Fan assembly
- PCB (Printed Circuit Board)
Related codes
F.41 Your boiler’s internal computer has lost its memory regarding the type of gas it should use, causing it to stop working for safety reasons.
Your boiler’s internal computer has lost its memory regarding the type of gas it should use, causing it to stop working for safety reasons.
Parts commonly replaced
- Printed Circuit Board (PCB)
Related codes
F.42 Your boiler is struggling to communicate with its internal components because of a damaged or loose wire inside the casing.
Your boiler is struggling to communicate with its internal components because of a damaged or loose wire inside the casing.
Parts commonly replaced
- Wiring harness
- Cable loom
- Printed Circuit Board connector
Related codes
Showing 21–30 of 59
F.43 Your boiler has detected an issue with its internal wiring connections, meaning it cannot communicate correctly between its own components and has safely shut down to prevent damage.
Your boiler has detected an issue with its internal wiring connections, meaning it cannot communicate correctly between its own components and has safely shut down to prevent damage.
Parts commonly replaced
- Wiring loom
- PCB (Printed Circuit Board)
Related codes
F.60 Your boiler has detected an internal electrical fault with the gas valve, which means it cannot safely light the flame to provide heating or hot water.
Your boiler has detected an internal electrical fault with the gas valve, which means it cannot safely light the flame to provide heating or hot water.
Parts commonly replaced
- Gas valve
- Main PCB (Printed Circuit Board)
- Wiring harness
Related codes
F.61 Your boiler has detected an electrical communication problem with the gas valve, which means it cannot safely light the flame to provide heating or hot water.
Your boiler has detected an electrical communication problem with the gas valve, which means it cannot safely light the flame to provide heating or hot water.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
- Gas valve
- Wiring harness
Related codes
F.62 Your boiler has identified a safety issue where the gas valve remains open or is leaking gas when it should be shut off, causing it to lock out for protection.
Your boiler has identified a safety issue where the gas valve remains open or is leaking gas when it should be shut off, causing it to lock out for protection.
Parts commonly replaced
- Gas Valve
- Printed Circuit Board (PCB)
Related codes
F.63 Your boiler's computer memory has developed a communication failure, preventing the internal system from starting up.
Your boiler's computer memory has developed a communication failure, preventing the internal system from starting up.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
Related codes
F.64 Your boiler has stopped working because its internal computer is receiving conflicting or faulty information from its temperature sensors.
Your boiler has stopped working because its internal computer is receiving conflicting or faulty information from its temperature sensors.
Parts commonly replaced
- NTC Temperature Sensors
- Printed Circuit Board (PCB)
- Wiring Harness
Related codes
F.65 Your boiler’s internal electronics have become too hot and have shut down to prevent damage to the control board.
Your boiler’s internal electronics have become too hot and have shut down to prevent damage to the control board.
Parts commonly replaced
- Main Printed Circuit Board (PCB)
- Electronic Control Box
Related codes
F.66 Your boiler's control panel is having trouble communicating with its internal computer, which means the system has stopped working to prevent further damage.
Your boiler's control panel is having trouble communicating with its internal computer, which means the system has stopped working to prevent further damage.
Parts commonly replaced
- User interface/Display PCB
- Main printed circuit board (PCB)
- Communication wiring harness
Related codes
F.67 Your boiler's main control board has detected a communication error with its flame sensing system, meaning it cannot safely confirm if the gas is lit.
Your boiler's main control board has detected a communication error with its flame sensing system, meaning it cannot safely confirm if the gas is lit.
Parts commonly replaced
- Main PCB (Printed Circuit Board)
- Ignition Electrode
- Flame Sensing Electrode
Related codes
S.00 Your boiler is currently in standby mode because it has not been asked to provide any heating.
Your boiler is currently in standby mode because it has not been asked to provide any heating.
What to check first
- Check your room thermostat is set to a higher temperature than the current room temperature.
- Ensure your programmer or heating timer is switched to the 'on' position.
- Verify that your thermostatic radiator valves are fully open.
Related codes
Showing 31–40 of 59
S.01 Your boiler is currently performing a normal startup routine where it clears the system before igniting, so it is likely functioning exactly as it should.
Your boiler is currently performing a normal startup routine where it clears the system before igniting, so it is likely functioning exactly as it should.
Related codes
S.02 Your boiler is simply preparing to start the heating process by circulating water, so this is a normal operational status rather than a fault.
Your boiler is simply preparing to start the heating process by circulating water, so this is a normal operational status rather than a fault.
Related codes
S.03 Your boiler is currently trying to light the gas flame to provide heating, so it is working normally and just going through its startup process.
Your boiler is currently trying to light the gas flame to provide heating, so it is working normally and just going through its startup process.
Related codes
S.04 Your boiler is operating normally and has successfully turned on the flames to provide heat to your radiators.
Your boiler is operating normally and has successfully turned on the flames to provide heat to your radiators.
Related codes
S.05 Your boiler is currently just finishing a normal cooling cycle, where it pushes heat away from the unit to protect its internal parts after being turned off.
Your boiler is currently just finishing a normal cooling cycle, where it pushes heat away from the unit to protect its internal parts after being turned off.
Related codes
S.07
Your boiler is simply performing a routine safety cycle where it keeps the pump running for a short time to move leftover heat away from the system, and this is completely normal behavior.
S.08 Your boiler is perfectly fine; it is currently in a brief, automatic rest period after just finishing a heating cycle to prevent overheating.
Your boiler is perfectly fine; it is currently in a brief, automatic rest period after just finishing a heating cycle to prevent overheating.
Related codes
S.10 Your boiler is currently operating normally as it is in the process of heating water for your taps or shower.
Your boiler is currently operating normally as it is in the process of heating water for your taps or shower.
Related codes
S.11 Your boiler is currently just running its internal fan to prepare for heating your water, which is a normal part of its startup process.
Your boiler is currently just running its internal fan to prepare for heating your water, which is a normal part of its startup process.
Related codes
S.13 Your boiler is currently trying to light the flame to heat your water, but it has not yet confirmed that the flame has successfully started.
Your boiler is currently trying to light the flame to heat your water, but it has not yet confirmed that the flame has successfully started.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Printed Circuit Board (PCB)
Related codes
Showing 41–50 of 59
S.14 Your boiler is currently operating normally as it heats water for your taps or shower.
Your boiler is currently operating normally as it heats water for your taps or shower.
Related codes
S.16 Your boiler is currently running its internal fan to clear out hot air after use, which is a normal part of the cooling process after you turn off a hot tap.
Your boiler is currently running its internal fan to clear out hot air after use, which is a normal part of the cooling process after you turn off a hot tap.
Related codes
S.17 Your boiler is currently cooling itself down after providing hot water, which is a normal part of its operating cycle.
Your boiler is currently cooling itself down after providing hot water, which is a normal part of its operating cycle.
Related codes
S.20
Your boiler is currently working correctly and is simply maintaining its internal temperature so that hot water is available to your taps instantly.
S.21 Your boiler is simply performing a routine check of its internal fan before starting to provide hot water.
Your boiler is simply performing a routine check of its internal fan before starting to provide hot water.
Related codes
S.23 Your boiler is currently going through its normal, safe process to ignite the flame for your hot water supply.
Your boiler is currently going through its normal, safe process to ignite the flame for your hot water supply.
Related codes
S.24
Your boiler is currently operating normally to maintain the temperature of your hot water system for faster delivery.
S.27
Your boiler is currently running its internal pump to move residual heat around the system after the hot water or heating has finished.
S.28 Your boiler is perfectly fine; this isn't a fault but a protective waiting period designed to prevent the system from turning on and off too frequently.
Your boiler is perfectly fine; this isn't a fault but a protective waiting period designed to prevent the system from turning on and off too frequently.
Related codes
S.30 Your boiler is currently in standby mode because it is not receiving a signal from your thermostat or timer to turn on the heating.
Your boiler is currently in standby mode because it is not receiving a signal from your thermostat or timer to turn on the heating.
What to check first
- Check your room thermostat is turned up higher than the current room temperature.
- Ensure your heating programmer or timer is set to an 'ON' period.
- Verify that any smart heating controls are connected to Wi-Fi and not showing an error message.
Related codes
Showing 51–59 of 59
S.31 Your boiler is perfectly fine; it is simply set to 'summer mode' which means it will provide hot water when you turn on a tap, but will not heat your radiators.
Your boiler is perfectly fine; it is simply set to 'summer mode' which means it will provide hot water when you turn on a tap, but will not heat your radiators.
What to check first
- Locate the radiator temperature dial on the front of the boiler control panel.
- Turn the dial clockwise to your desired temperature setting.
- The boiler will automatically switch from 'summer mode' to normal operation.
Related codes
S.32 Your boiler has paused its operations because it detected a problem with the fan's speed, which triggers a safety feature to prevent the internal pipes from freezing.
Your boiler has paused its operations because it detected a problem with the fan's speed, which triggers a safety feature to prevent the internal pipes from freezing.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
- Hall sensor
Related codes
S.33 Your boiler has paused because it is struggling to breathe clearly, meaning it cannot pull in fresh air or push out exhaust fumes correctly.
Your boiler has paused because it is struggling to breathe clearly, meaning it cannot pull in fresh air or push out exhaust fumes correctly.
Parts commonly replaced
- Air pressure switch
- Flue fan
- Venturi assembly
Related codes
S.34 Your boiler is temporarily running its pump to prevent the water inside from freezing because the temperature around the pipes has dropped low.
Your boiler is temporarily running its pump to prevent the water inside from freezing because the temperature around the pipes has dropped low.
Related codes
S.36 Your boiler is currently in standby mode because it is not receiving a signal from your thermostat to turn on the heating.
Your boiler is currently in standby mode because it is not receiving a signal from your thermostat to turn on the heating.
What to check first
- Check your room thermostat and turn the target temperature up higher than the current room temperature.
- Ensure your programmer or timer is set to an 'On' period for heating.
- Replace the batteries in your wireless thermostat if applicable.
Related codes
S.39 Your boiler has detected that the water in your underfloor heating circuit has become too hot and has automatically shut down to prevent damage to your flooring.
Your boiler has detected that the water in your underfloor heating circuit has become too hot and has automatically shut down to prevent damage to your flooring.
Parts commonly replaced
- Limit thermostat
- Pump
- Mixing valve
Related codes
S.52 Your boiler is currently trying to light the flame, which is a normal part of its startup sequence if it has been off for a moment.
Your boiler is currently trying to light the flame, which is a normal part of its startup sequence if it has been off for a moment.
Related codes
S.53 Your boiler is temporarily paused because it has detected that the water pressure inside the heating system is too low to run safely.
Your boiler is temporarily paused because it has detected that the water pressure inside the heating system is too low to run safely.
What to check first
- Locate the external filling loop, usually a small braided metal hose found underneath the boiler.
- Open the valves one at a time to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
- Ensure both valves are fully closed again and wait 2-3 minutes for the system to restart automatically.
Parts commonly replaced
- Filling loop
- Pressure relief valve
- Pressure gauge
Related codes
S.54 Your boiler has temporarily entered a cooling-down pause because the water inside is heating up too quickly.
Your boiler has temporarily entered a cooling-down pause because the water inside is heating up too quickly.
What to check first
- Check that all radiator valves are fully open
- Ensure the boiler pressure is between 1.0 and 1.5 bar
- Remove any obstructions from magnets or external system filters
- Bleed any air from the radiators
Parts commonly replaced
- Central heating pump
- System filter
- Heat exchanger