BoilerFaultCodes d.00
This code is not a fault; it simply indicates that your boiler is currently running at a lower power setting to save energy.
Vaillant ecoTEC plus Aquaplus Fault codes & diagnostics
94 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Natural Gas 24-28 kW 2006-2012 Discontinued
Replaced by: ecoTEC plus
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Severity at a glance
Each cell = one fault code. Hover to identify. 1 Emergency
35 High
9 Medium
49 Low
Just want the most common Vaillant ecoTEC plus Aquaplus faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 94 documented codes
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d.01 Your boiler is currently running its internal pump to move excess heat away from the system, which is a normal part of the cooling-down process after your heating or hot water has been active.
Your boiler is currently running its internal pump to move excess heat away from the system, which is a normal part of the cooling-down process after your heating or hot water has been active.
Related codes
d.02 Your boiler is currently protecting itself by waiting for a short period before restarting to prevent unnecessary wear and tear.
Your boiler is currently protecting itself by waiting for a short period before restarting to prevent unnecessary wear and tear.
Related codes
d.03
This code is simply showing you the current temperature of the hot water inside your boiler, rather than indicating a fault.
d.04
This code is simply showing you the current temperature reading of the hot water inside your boiler's internal storage tank.
d.05
Your boiler is currently monitoring or measuring the temperature of the water as it leaves the unit to heat your home.
d.06
Your boiler is simply displaying the current setting for your hot water temperature and is not indicating a fault.
d.08 Your boiler is receiving a signal from your thermostat or smart controller to turn on the heating, so it is simply working as intended.
Your boiler is receiving a signal from your thermostat or smart controller to turn on the heating, so it is simply working as intended.
Related codes
d.10 Your boiler is currently running a diagnostic check to confirm that the internal water pump is operating correctly.
Your boiler is currently running a diagnostic check to confirm that the internal water pump is operating correctly.
Parts commonly replaced
- Central heating pump
- PCB
Related codes
d.11 Your boiler is signalling that it is unable to detect or communicate with the external water pump responsible for moving heated water around your home.
Your boiler is signalling that it is unable to detect or communicate with the external water pump responsible for moving heated water around your home.
Parts commonly replaced
- External circulation pump
- Wiring harness
- Printed Circuit Board (PCB)
Related codes
Showing 11–20 of 94
d.12 Your boiler is signalling that the small pump responsible for moving hot water to your taps or storage cylinder is not receiving the expected electrical signal.
Your boiler is signalling that the small pump responsible for moving hot water to your taps or storage cylinder is not receiving the expected electrical signal.
Parts commonly replaced
- DHW pump
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
d.13 Your boiler is struggling to detect or activate the small pump responsible for moving hot water around your house, meaning you might notice a delay in getting hot water at your taps.
Your boiler is struggling to detect or activate the small pump responsible for moving hot water around your house, meaning you might notice a delay in getting hot water at your taps.
Parts commonly replaced
- External DHW pump
- Pump wiring harness
- PCB
d.21 Your boiler is struggling to detect that the flame is lit, so it is turning itself off to ensure your safety.
Your boiler is struggling to detect that the flame is lit, so it is turning itself off to ensure your safety.
Parts commonly replaced
- Ignition electrode
- Flame rectification lead
- PCB
Related codes
d.22
Your boiler has received a request to provide hot water and is operating exactly as it should.
d.23 Your boiler is currently indicating that it is adjusting its internal settings for the seasonal transition between heating and hot water mode.
Your boiler is currently indicating that it is adjusting its internal settings for the seasonal transition between heating and hot water mode.
What to check first
- Check the position of the physical central heating control knob on the front panel
- Rotate the knob to your desired temperature setting to ensure it is not stuck between modes
- Observe the display to see if the code clears once the setting is firmly selected
d.24 Your boiler is struggling because it cannot detect that the air required for safe combustion is flowing correctly.
Your boiler is struggling because it cannot detect that the air required for safe combustion is flowing correctly.
Parts commonly replaced
- Air pressure switch
- Fan assembly
- Venturi
- Flue sensing tubes
Related codes
d.25 Your boiler is currently monitoring the status or temperature of the integrated hot water storage tank.
Your boiler is currently monitoring the status or temperature of the integrated hot water storage tank.
Parts commonly replaced
- NTC sensor
- Wiring harness
d.30 Your boiler is struggling to detect or control the gas flow needed to light the flame, so it has safely shut itself down to prevent a malfunction.
Your boiler is struggling to detect or control the gas flow needed to light the flame, so it has safely shut itself down to prevent a malfunction.
Parts commonly replaced
- Gas valve
- Main PCB
- Wiring harness
Related codes
d.33 Your boiler is struggling to operate its internal extraction fan, which prevents the unit from starting the heating or hot water process safely.
Your boiler is struggling to operate its internal extraction fan, which prevents the unit from starting the heating or hot water process safely.
Parts commonly replaced
- Fan unit
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
d.34 Your boiler is simply displaying the current operating speed of its internal fan, which is a normal piece of technical information rather than a fault code.
Your boiler is simply displaying the current operating speed of its internal fan, which is a normal piece of technical information rather than a fault code.
Related codes
Showing 21–30 of 94
d.35 Your boiler is struggling to switch between heating your house and heating your hot water taps, which may cause one of these services to stop working correctly.
Your boiler is struggling to switch between heating your house and heating your hot water taps, which may cause one of these services to stop working correctly.
Parts commonly replaced
- Diverter valve actuator
- Diverter valve cartridge
- Diverter valve motor
Related codes
d.37 Your boiler is having difficulty communicating correctly with its internal gas control system, which prevents it from firing up safely.
Your boiler is having difficulty communicating correctly with its internal gas control system, which prevents it from firing up safely.
Parts commonly replaced
- Gas valve
- Main printed circuit board (PCB)
- Wiring harness
Related codes
d.40 This code is simply a status message showing the current temperature of the water flowing through your heating system, not an error or a fault with your boiler.
This code is simply a status message showing the current temperature of the water flowing through your heating system, not an error or a fault with your boiler.
Related codes
d.41
This code is simply a diagnostic reading that shows the current temperature of the water returning to your boiler, rather than an error that requires fixing.
d.50 Your boiler has detected that the water inside the unit is getting hotter than the safety controls allow, so it has shut down to prevent damage.
Your boiler has detected that the water inside the unit is getting hotter than the safety controls allow, so it has shut down to prevent damage.
Parts commonly replaced
- NTC Sensor
- Pump
- Primary Heat Exchanger
Related codes
d.60 Your boiler has detected that it has shut itself down due to overheating multiple times and is now logging these events as a warning.
Your boiler has detected that it has shut itself down due to overheating multiple times and is now logging these events as a warning.
Parts commonly replaced
- Pump
- System filter
- Diverter valve
- Heat exchanger
Related codes
d.61 Your boiler has recorded several automatic safety shutdowns recently, which indicates that it is struggling to operate consistently.
Your boiler has recorded several automatic safety shutdowns recently, which indicates that it is struggling to operate consistently.
Parts commonly replaced
- Ignition electrode
- Flame sensor
- Gas valve
Related codes
d.64 Your boiler is recording how long it takes to light the flame, which is a background status check rather than a breakdown.
Your boiler is recording how long it takes to light the flame, which is a background status check rather than a breakdown.
Related codes
F.00 Your boiler's temperature sensor is failing to provide a signal, meaning the system has safely shut down to prevent overheating.
Your boiler's temperature sensor is failing to provide a signal, meaning the system has safely shut down to prevent overheating.
Parts commonly replaced
- Flow temperature sensor (NTC)
- Wiring harness
Related codes
F.01 Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has shut down to prevent potential damage.
Your boiler has lost the ability to accurately measure the temperature of the water returning to it, so it has shut down to prevent potential damage.
Parts commonly replaced
- Return NTC sensor
- Wiring harness
Related codes
Showing 31–40 of 94
F.02 Your boiler is having trouble sensing the temperature of your hot water supply, which means it has stopped providing hot water to prevent overheating.
Your boiler is having trouble sensing the temperature of your hot water supply, which means it has stopped providing hot water to prevent overheating.
Parts commonly replaced
- Domestic Hot Water (DHW) NTC temperature sensor
- Wiring harness
Related codes
F.03 Your boiler has lost the connection to the temperature sensor inside your hot water tank, meaning it cannot determine how hot your water is.
Your boiler has lost the connection to the temperature sensor inside your hot water tank, meaning it cannot determine how hot your water is.
Parts commonly replaced
- Hot water cylinder sensor
- Wiring harness
Related codes
F.10 Your boiler has detected a faulty electrical signal from its internal temperature sensor, causing it to shut down for safety.
Your boiler has detected a faulty electrical signal from its internal temperature sensor, causing it to shut down for safety.
Parts commonly replaced
- Flow NTC sensor
- Wiring harness
Related codes
F.11 Your boiler has detected an electrical fault with one of its temperature sensors, meaning it cannot accurately monitor the water returning to the system and has shut down as a precaution.
Your boiler has detected an electrical fault with one of its temperature sensors, meaning it cannot accurately monitor the water returning to the system and has shut down as a precaution.
Parts commonly replaced
- Return NTC sensor
- Wiring harness
Related codes
F.12 Your boiler has detected a faulty electrical connection or sensor related to the hot water temperature, which stops it from heating your water until it is fixed.
Your boiler has detected a faulty electrical connection or sensor related to the hot water temperature, which stops it from heating your water until it is fixed.
Parts commonly replaced
- DHW NTC sensor
- Wiring harness
Related codes
F.13 Your boiler has lost the ability to accurately measure the temperature of the water inside your hot water storage tank due to a faulty sensor or a loose electrical connection.
Your boiler has lost the ability to accurately measure the temperature of the water inside your hot water storage tank due to a faulty sensor or a loose electrical connection.
Parts commonly replaced
- Domestic Hot Water NTC Sensor
- Wiring harness
Related codes
F.20 Your boiler has automatically turned itself off because it has become dangerously overheated to prevent damage or safety hazards.
Your boiler has automatically turned itself off because it has become dangerously overheated to prevent damage or safety hazards.
Parts commonly replaced
- NTC temperature sensor
- Pump
- Primary heat exchanger
- PCB
Related codes
F.22 Your boiler has detected that there is not enough water inside the system to operate safely, which has caused it to shut down to prevent damage.
Your boiler has detected that there is not enough water inside the system to operate safely, which has caused it to shut down to prevent damage.
What to check first
- Locate the pressure gauge on the front of your boiler.
- Check if the needle is below the 1.0 bar mark.
- Use the filling loop (a metal braided hose or key under the boiler) to top up the system pressure until the needle reaches between 1.0 and 1.5 bar.
Parts commonly replaced
- Central heating pump
- Pressure sensor
- System expansion vessel
Related codes
F.23 Your boiler has detected that water is not circulating properly, meaning it cannot safely heat the system.
Your boiler has detected that water is not circulating properly, meaning it cannot safely heat the system.
Parts commonly replaced
- Central heating pump
- NTC sensors
- Printed Circuit Board (PCB)
Related codes
F.24 Your boiler has detected that it is heating up too quickly, which usually means there is air trapped inside the system or water is not circulating properly.
Your boiler has detected that it is heating up too quickly, which usually means there is air trapped inside the system or water is not circulating properly.
Parts commonly replaced
- Central heating pump
- System filter
- Heat exchanger
Related codes
Showing 41–50 of 94
F.27 Your boiler has detected an internal failure that is preventing it from safely starting the fuel supply to create heat.
Your boiler has detected an internal failure that is preventing it from safely starting the fuel supply to create heat.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Gas Valve
- Wiring Harness
Related codes
F.28 Your boiler has failed to ignite and has shut itself down as a safety precaution because it cannot detect a flame.
Your boiler has failed to ignite and has shut itself down as a safety precaution because it cannot detect a flame.
Parts commonly replaced
- Ignition electrode
- Gas valve
- Main PCB
Related codes
F.29 Your boiler is trying to start but the flame keeps going out, which usually means it cannot get the gas it needs to stay running.
Your boiler is trying to start but the flame keeps going out, which usually means it cannot get the gas it needs to stay running.
Parts commonly replaced
- Gas valve
- Ignition electrode
- Condensate trap
- Printed circuit board (PCB)
Related codes
F.32 Your boiler has detected an issue with the internal fan that pushes air for combustion, causing it to pause operations to prevent potential freezing or damage.
Your boiler has detected an issue with the internal fan that pushes air for combustion, causing it to pause operations to prevent potential freezing or damage.
Parts commonly replaced
- Fan
- Wiring harness
- PCB
Related codes
F.33 Your boiler has detected an issue with its internal airflow system, so it has safely shut down to prevent potential damage.
Your boiler has detected an issue with its internal airflow system, so it has safely shut down to prevent potential damage.
Parts commonly replaced
- Air pressure switch
- Fan unit
- Venturi nozzle
- Wiring harness
Related codes
F.37 Your boiler has detected that the internal fan responsible for moving air is not spinning at the correct speed, which prevents it from firing up safely.
Your boiler has detected that the internal fan responsible for moving air is not spinning at the correct speed, which prevents it from firing up safely.
Parts commonly replaced
- Fan unit
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
F.41 Your boiler has lost its internal digital settings and is currently unable to recognize how it should be operating, leaving you without heating or hot water.
Your boiler has lost its internal digital settings and is currently unable to recognize how it should be operating, leaving you without heating or hot water.
Parts commonly replaced
- Main PCB
Related codes
F.42 Your boiler has detected a problem with its internal wiring connections that is preventing it from communicating properly with its internal safety controls.
Your boiler has detected a problem with its internal wiring connections that is preventing it from communicating properly with its internal safety controls.
Parts commonly replaced
- Wiring harness
- Gas valve connection
- PCB
Related codes
F.43 Your boiler's internal wiring has developed a communication failure, meaning the safety systems can no longer properly connect to the main control board.
Your boiler's internal wiring has developed a communication failure, meaning the safety systems can no longer properly connect to the main control board.
Parts commonly replaced
- Wiring harness
- Main PCB
Related codes
F.60 Your boiler's main computer control unit is experiencing an internal error and cannot safely operate the system.
Your boiler's main computer control unit is experiencing an internal error and cannot safely operate the system.
Parts commonly replaced
- Printed Circuit Board (PCB)
Related codes
Showing 51–60 of 94
F.61 Your boiler's internal computer has detected a critical electrical error and has shut down to prevent further damage.
Your boiler's internal computer has detected a critical electrical error and has shut down to prevent further damage.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
F.62 Your boiler has detected that gas might still be present even after it has tried to shut off, meaning it has safely locked itself to prevent a potential hazard.
Your boiler has detected that gas might still be present even after it has tried to shut off, meaning it has safely locked itself to prevent a potential hazard.
Parts commonly replaced
- Gas valve
- Printed Circuit Board (PCB)
Related codes
F.63 Your boiler's main control computer is experiencing a communication or internal electrical fault, meaning it can no longer safely operate the system.
Your boiler's main control computer is experiencing a communication or internal electrical fault, meaning it can no longer safely operate the system.
Parts commonly replaced
- Main PCB
- Wiring harness
Related codes
F.64 Your boiler has detected an internal electrical glitch or a faulty sensor reading, which has caused it to stop working to avoid potential damage.
Your boiler has detected an internal electrical glitch or a faulty sensor reading, which has caused it to stop working to avoid potential damage.
Parts commonly replaced
- Main PCB
- NTC sensor
Related codes
F.65 Your boiler’s internal control system has detected that it is overheating, causing it to shut down for safety.
Your boiler’s internal control system has detected that it is overheating, causing it to shut down for safety.
Parts commonly replaced
- Main PCB
- Wiring harness
Related codes
F.66 Your boiler's control panel has lost communication with the main internal computer, preventing the boiler from receiving instructions on how to operate.
Your boiler's control panel has lost communication with the main internal computer, preventing the boiler from receiving instructions on how to operate.
Parts commonly replaced
- User interface/display module
- Main PCB (Printed Circuit Board)
- Wiring harness
Related codes
F.67 Your boiler's internal computer is having difficulty communicating with its main control unit, causing the system to stop working as a safety precaution.
Your boiler's internal computer is having difficulty communicating with its main control unit, causing the system to stop working as a safety precaution.
Parts commonly replaced
- Main PCB
- Wiring harness
Related codes
P.11 Your boiler is currently running an internal calibration test to ensure it is burning gas correctly at its mid-range setting.
Your boiler is currently running an internal calibration test to ensure it is burning gas correctly at its mid-range setting.
Related codes
P.12 Your boiler is undergoing a standard automatic self-test procedure during startup and is temporarily pausing to check its internal systems.
Your boiler is undergoing a standard automatic self-test procedure during startup and is temporarily pausing to check its internal systems.
Related codes
P.13
Your boiler is currently running a specific internal procedure to calibrate its settings for the type of gas being used.
Showing 61–70 of 94
S.00 Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water, so it is working exactly as it should.
Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water, so it is working exactly as it should.
What to check first
- Check your room thermostat to ensure it is set to a temperature higher than the current room temperature
- Ensure your heating programmer or timer is set to 'on'
- Check that your hot water demand is active if you require a tank refill
Related codes
S.01 Your boiler is currently initiating the startup process to prepare for heating your home.
Your boiler is currently initiating the startup process to prepare for heating your home.
Related codes
S.02 Your boiler is simply performing a routine task by circulating water through your heating system, which is a normal part of its operation.
Your boiler is simply performing a routine task by circulating water through your heating system, which is a normal part of its operation.
Related codes
S.03 Your boiler is currently trying to light the flame to start heating your home, which is a normal part of its automatic start-up process.
Your boiler is currently trying to light the flame to start heating your home, which is a normal part of its automatic start-up process.
Related codes
S.4
Your boiler is operating normally and is currently heating your home or water as requested.
S.04 Your boiler is currently operating normally as it is in the process of lighting the flame to provide heating for your home.
Your boiler is currently operating normally as it is in the process of lighting the flame to provide heating for your home.
Related codes
S.05 Your boiler is simply performing a routine cooling-down process after your heating has been running, which is completely normal operation.
Your boiler is simply performing a routine cooling-down process after your heating has been running, which is completely normal operation.
Related codes
S.06 Your boiler is simply finishing its cooling process after being used, which is completely normal and means the system is safely shutting down.
Your boiler is simply finishing its cooling process after being used, which is completely normal and means the system is safely shutting down.
Related codes
S.07 Your boiler is simply finishing a cooling-down cycle after being used for heating, which is a normal part of its operation.
Your boiler is simply finishing a cooling-down cycle after being used for heating, which is a normal part of its operation.
Related codes
S.08 Your boiler is currently taking a mandatory short break to prevent wear and tear, and it will automatically resume heating shortly.
Your boiler is currently taking a mandatory short break to prevent wear and tear, and it will automatically resume heating shortly.
Related codes
Showing 71–80 of 94
S.10 Your boiler is currently heating water for your taps or shower, and this code is simply a status message confirming it is working as expected.
Your boiler is currently heating water for your taps or shower, and this code is simply a status message confirming it is working as expected.
Related codes
S.11 Your boiler is simply preparing to heat your water by starting its internal ventilation fan, which is a normal part of the startup cycle.
Your boiler is simply preparing to heat your water by starting its internal ventilation fan, which is a normal part of the startup cycle.
Related codes
S.13 Your boiler is currently trying to light its flame to begin heating domestic hot water.
Your boiler is currently trying to light its flame to begin heating domestic hot water.
Related codes
S.14
Your boiler is operating normally and is successfully providing hot water to your home.
S.15 Your boiler is currently cooling itself down after recently heating your water, which is a normal part of its automatic shutdown process.
Your boiler is currently cooling itself down after recently heating your water, which is a normal part of its automatic shutdown process.
Related codes
S.16 Your boiler is simply performing a routine cooling process for the fan after you have finished using hot water, and it will turn off automatically once the temperature settles.
Your boiler is simply performing a routine cooling process for the fan after you have finished using hot water, and it will turn off automatically once the temperature settles.
Related codes
S.17 Your boiler is currently performing a standard task where it moves hot water around the system after it has finished heating your water supply, and this is a normal part of its operation.
Your boiler is currently performing a standard task where it moves hot water around the system after it has finished heating your water supply, and this is a normal part of its operation.
Related codes
S.20 Your boiler is currently refilling the internal hot water storage tank, which happens automatically to ensure you have a steady supply of hot water.
Your boiler is currently refilling the internal hot water storage tank, which happens automatically to ensure you have a steady supply of hot water.
Related codes
S.21 Your boiler is currently heating up the internal hot water storage tank, which is a normal part of its operation.
Your boiler is currently heating up the internal hot water storage tank, which is a normal part of its operation.
Related codes
S.23 Your boiler is currently heating the internal water storage tank to ensure you have hot water ready to use.
Your boiler is currently heating the internal water storage tank to ensure you have hot water ready to use.
Related codes
Showing 81–90 of 94
S.24 Your boiler is currently busy heating up the internal hot water storage tank, which is a normal part of its operation.
Your boiler is currently busy heating up the internal hot water storage tank, which is a normal part of its operation.
Related codes
S.25 Your boiler is currently working normally to top up the temperature of its internal hot water storage tank.
Your boiler is currently working normally to top up the temperature of its internal hot water storage tank.
Related codes
S.26 Your boiler is currently running its fan to prepare the hot water storage tank, which is a normal part of the heating cycle.
Your boiler is currently running its fan to prepare the hot water storage tank, which is a normal part of the heating cycle.
Related codes
S.27 Your boiler is currently moving hot water around its internal tank to make sure your hot water supply is ready for use, which is a normal part of the system's operation.
Your boiler is currently moving hot water around its internal tank to make sure your hot water supply is ready for use, which is a normal part of the system's operation.
Related codes
S.28 Your boiler is perfectly fine; this is just a normal temporary pause where the system is waiting for the hot water storage tank to heat up before it lets the central heating turn back on.
Your boiler is perfectly fine; this is just a normal temporary pause where the system is waiting for the hot water storage tank to heat up before it lets the central heating turn back on.
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 and ensure it is set to a temperature higher than the current room temperature.
- Verify that your heating programmer or smart app is currently set to an 'On' period.
- Check if any external boiler controls or wireless receivers have power and are properly linked to the boiler.
Related codes
S.31 Your boiler is perfectly healthy and is currently set to only provide hot water while the central heating is switched off for the summer.
Your boiler is perfectly healthy and is currently set to only provide hot water while the central heating is switched off for the summer.
What to check first
- Locate the heating control knob on the front panel of your boiler
- Turn the knob clockwise to your desired temperature setting
- Observe the display as the S.31 screen message disappears
S.32 Your boiler has detected that the fan is not spinning at the correct speed to keep the internal components safe, so it has paused operation to prevent damage.
Your boiler has detected that the fan is not spinning at the correct speed to keep the internal components safe, so it has paused operation to prevent damage.
Parts commonly replaced
- Fan assembly
- Printed Circuit Board (PCB)
Related codes
S.33 Your boiler is struggling to breathe because it has detected an issue with the air intake or exhaust system.
Your boiler is struggling to breathe because it has detected an issue with the air intake or exhaust system.
Parts commonly replaced
- Air pressure switch
- Flue gasket
- Fan assembly
Related codes
S.34 Your boiler has detected very cold temperatures and is running its pump to prevent your pipes from freezing.
Your boiler has detected very cold temperatures and is running its pump to prevent your pipes from freezing.
What to check first
- Ensure your heating is set to a schedule that prevents the house temperature from dropping too low
- Check that your external frost thermostat is not set too low
- Ensure the boiler remains switched on at the mains so it can protect itself
Related codes
Showing 91–94 of 94
S.36 Your boiler is currently idle because it has not received a signal from your thermostat or timer to turn on the heating.
Your boiler is currently idle because it has not received a signal from your thermostat or timer to turn on the heating.
What to check first
- Check that your room thermostat or smart controller is set to a temperature higher than the current room temperature.
- Verify that your heating programmer or central heating timer is currently set to 'on'.
- Replace the batteries in your wireless thermostat or receiver unit if applicable.
Related codes
S.39 Your boiler has detected that the water temperature in your underfloor heating circuit is too high, so it has temporarily shut down to prevent damage to your flooring.
Your boiler has detected that the water temperature in your underfloor heating circuit is too high, so it has temporarily shut down to prevent damage to your flooring.
Parts commonly replaced
- Underfloor heating contact thermostat
- System pump
- Mixing valve
Related codes
S.53 Your boiler has detected low water pressure and is pausing operation for a few minutes to protect its internal pump from damage.
Your boiler has detected low water pressure and is pausing operation for a few minutes to protect its internal pump from damage.
What to check first
- Check your boiler's pressure gauge on the front display; if it is below 1.0 bar, the system needs more water.
- Locate the external filling loop (a silver flexi-hose) beneath the boiler.
- Open the valves on the filling loop to allow water into the system until the gauge reaches 1.5 bar, then ensure valves are fully closed.
Parts commonly replaced
- Filling loop
- Pressure sensor/transducer
Related codes
S.54 Your boiler has temporarily stopped itself because the water inside is heating up much faster than the system can circulate it away.
Your boiler has temporarily stopped itself because the water inside is heating up much faster than the system can circulate it away.
What to check first
- Ensure all radiator valves are fully open to allow water to circulate freely
- Check that your external room thermostat is not set drastically higher than the current room temperature
- Wait 15 minutes to see if the boiler restarts automatically once the water temperature levels out
Parts commonly replaced
- Central heating pump
- Diverter valve
- System filter