Vaillant Combi Compact 282EB Fault codes & diagnostics

164 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24 kW 1994-2002 Discontinued

Replaced by: Turbomax

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Each cell = one fault code. Hover to identify.
1 Emergency 85 High 21 Medium 57 Low

All 164 documented codes

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CONNECTION

Your boiler's internal components are failing to talk to each other, meaning the system cannot start up to provide heat or hot water.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness
  • Display PCB

Related codes

D,11

Your boiler's external pump, which helps push heat around your home, has stopped working correctly.

High Engineer only £180-350

Parts commonly replaced

  • External central heating pump
  • Pump wiring harness
  • Relay PCB

Related codes

D.0

Your boiler is currently restricted to a lower power setting for heating, meaning your radiators might take much longer than usual to get warm.

Low Engineer only £60-120

Parts commonly replaced

  • Gas valve (adjustment)
  • Main PCB

Related codes

D.1

Your boiler is simply cooling itself down after providing heat, which is a normal part of its operation rather than a breakdown.

Low DIY-safe

What to check first

  1. Wait for the pump symbol or code to clear automatically as it completes its cycle
  2. Ensure your radiator valves are open to allow water to circulate easily
  3. Check if your thermostat is still calling for heat

Related codes

D.2

Your boiler is temporarily resting because it has reached its target temperature and is waiting for the water to cool down slightly before firing up again to save energy.

Low DIY-safe

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature
  2. Ensure your radiator valves are open to allow heat to dissipate
  3. Wait approximately 15 to 30 minutes for the timer to reset and the boiler to restart automatically

Related codes

D.3

Your boiler's internal computer is currently displaying the live temperature of your hot water rather than showing a specific fault code.

Low DIY-safe

What to check first

  1. Wait 5 seconds for the screen to revert to the system pressure or status
  2. Press the 'i' button to toggle back to the main display
  3. Turn the hot water tap off if it is currently running

Related codes

D.4

Your boiler is currently showing the live temperature reading of the 'warm start' sensor, which keeps a small amount of water pre-heated for faster hot water delivery.

Low DIY-safe £0-90

What to check first

  1. Check if the 'Comfort' or 'Warm Start' knob is turned on.
  2. Wait a few moments to see if the display changes back to the system pressure or main temperature.
  3. If the code persists without the boiler firing, try a simple reset using the flame/cross button.

Parts commonly replaced

  • Warm start NTC thermistor
  • Wiring harness

Related codes

D.5

Your boiler is currently waiting for the water temperature to drop or is processing a specific demand for heat, which is a normal operational status rather than a breakdown.

Low DIY-safe

What to check first

  1. Check if your thermostat is turned up or calling for heat
  2. Ensure radiators are turned on
  3. Wait up to 10 minutes to see if the code changes to a heating symbol

Related codes

D.7

Your boiler is displaying the current temperature setting for the 'warm start' feature, which keeps a small amount of water pre-heated so you get hot water at your taps more quickly.

Low DIY-safe

What to check first

  1. Locate the hot water temperature control knob on the front panel.
  2. Turn the knob clockwise to increase the pre-heat temperature, or anti-clockwise to decrease it.
  3. Observe the display change as you adjust the target value to your preference.

Related codes

D.8

Your boiler is receiving a signal from your external thermostat or timer telling it to provide heating or hot water, and it is behaving as it should.

Low DIY-safe

What to check first

  1. Check your external room thermostat or smart home app to see if heating is turned on
  2. Verify that your mechanical timer or programmer is set to an 'on' period
  3. If you do not want the heating on, turn down your room thermostat or adjust your timer settings

Related codes

Showing 11–20 of 164
D.9

Your boiler is receiving a instruction from an external thermostat or home automation system telling it what temperature to run at.

Low DIY-safe £0-120

What to check first

  1. Check your external room thermostat or smart heating controls are set to the desired temperature
  2. Ensure any external 'eBUS' or analogue controllers are powered on and connected
  3. Restart your heating controls to refresh the signal to the boiler

Parts commonly replaced

  • External Room Thermostat
  • Analogue Control Module
  • Wiring Loom

Related codes

D.10

Your boiler is unable to circulate water around the system because its internal pump has stopped working or is jammed.

High Engineer only £220-£450

Parts commonly replaced

  • Internal Heating Pump
  • Pump Capacitor
  • Wiring Harness

Related codes

D.12

Your boiler is having trouble communicating with the pump that fills your hot water cylinder, which may result in a lack of hot water.

High Engineer only £180-350

Parts commonly replaced

  • Cylinder charging pump
  • Accessory module (VR 40)
  • Wiring harness

Related codes

D.13

Your boiler is having trouble circulating hot water through the system, which typically means the internal pump is stuck or has failed.

High Engineer only £220-£450

Parts commonly replaced

  • Hot water circulation pump
  • Pump capacitor
  • PCB

Related codes

D.14

Your boiler is struggling to set the correct speed for the internal pump that moves water through the system.

Medium Engineer only £180-£350

Parts commonly replaced

  • Circulation Pump
  • Main PCB

Related codes

D.15

Your boiler's internal pump is running at an incorrect speed, which prevents the system from moving heat to your taps or radiators effectively.

High Engineer only £180-350

Parts commonly replaced

  • Circulation Pump
  • PCB (Printed Circuit Board)
  • Wiring Harness

Related codes

D.17

Your boiler has sensed that the water returning from your radiators is hotter than it should be, causing the system to temporarily throttle back its power.

Low DIY-safe £80-220

What to check first

  1. Check that all radiator valves (TRVs) are fully open
  2. Ensure the central heating bypass valve is not closed
  3. Check for any obstructions to airflow around radiators
  4. Monitor the boiler to see if the code clears after the system cools

Parts commonly replaced

  • Central heating return thermistor
  • Circulation pump
  • Main heat exchanger (flushing)

Related codes

D.18

Your boiler is currently set to run the internal pump continuously, often due to a specific setting or a need to prevent the pipes from freezing.

Low DIY-safe £0-80

What to check first

  1. Check if the comfort mode or pre-heat setting is turned on
  2. Ensure your external thermostat is not calling for heat constantly
  3. Reset the boiler to see if the status code clears

Parts commonly replaced

  • None (Setting adjustment)
  • External Thermostat

Related codes

D.19

Your boiler is having trouble managing the speed of its internal pump, which may lead to inefficient heating or your system struggling to circulate water properly.

Medium Engineer only £180-£350

Parts commonly replaced

  • Circulation Pump
  • PCB (Printed Circuit Board)
  • Pump Relay

Related codes

D.20

Your boiler is currently ignoring the temperature dial because it has reached the maximum pre-set safety limit for your hot water storage.

Low DIY-safe £0-80

What to check first

  1. Turn the hot water temperature dial down slightly
  2. Run a hot tap for a minute to reduce the cylinder temperature
  3. Check if the display returns to a standard status code after a few minutes

Parts commonly replaced

  • NTC Temperature Sensor
  • Hot water potentiometer

Related codes

Showing 21–30 of 164
D.22

Your boiler is signalling that it is currently busy preparing or providing hot water through your taps.

Low DIY-safe

What to check first

  1. Check if any hot water taps are slightly open or dripping
  2. Ensure there are no leaks in your hot water pipework
  3. Turn off the tap and wait for the boiler to return to its normal heating mode
D.23

Your boiler is currently set to summer mode, which means your hot water is working but your central heating has been deactivated.

Low DIY-safe

What to check first

  1. Locate the radiator symbol control knob on the front panel.
  2. Turn the knob clockwise to the desired temperature setting to activate winter mode.
  3. Check that your room thermostat is turned up to call for heat.

Related codes

D.24

Your boiler's internal water pressure is dropping too low while the pump is running, which usually points to a leak or a lack of water in the system.

High DIY-safe £60-180

What to check first

  1. Check the pressure gauge on the front of the boiler; it should ideally be between 1 and 1.5 bar.
  2. Locate the external filling loop beneath the boiler and slowly turn the valve to top up the water pressure.
  3. Inspect all visible radiator valves and pipework for signs of water leaks.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure relief valve

Related codes

D.25

Your boiler is currently providing hot water because it has received a digital request from your external heating controls or smart thermostat.

Low DIY-safe

What to check first

  1. Check if a hot water tap is turned on
  2. Check if your smart thermostat 'boost' or 'schedule' for hot water is active
  3. Turn off any active hot water demand on your control panel to see if the code clears

Related codes

D.26

Your boiler is having trouble communicating with an internal component or external accessory, which may prevent your heating or hot water from turning on correctly.

High Engineer only £120-250

Parts commonly replaced

  • Additional relay module
  • PCB (Printed Circuit Board)
  • Wiring harness

Related codes

D.27

Your boiler is having trouble communicating with an internal switch that controls an external accessory or heating component.

Medium Engineer only £120-280

Parts commonly replaced

  • Main PCB
  • Accessory Relay Module
  • Wiring Harness

Related codes

D.28

Your boiler is experiencing a communication fault with internal electrical switching components, usually meaning an accessory part is not responding correctly.

High Engineer only £120-280

Parts commonly replaced

  • Main PCB
  • Relay board
  • External control interface

Related codes

D.30

Your boiler is struggling to open the gas supply because of a communication issue between the electronics and the internal gas valves.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB
  • Gas Valve Assembly
  • Wiring Harness

Related codes

D.33

Your boiler has identified a problem with the fan that clears away waste gases, causing the system to shut down for safety.

High Engineer only £180-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

D.34

Your boiler has detected that the internal fan is spinning at the wrong speed, preventing the system from clearing waste gases and starting up safely.

High Engineer only £180-£350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Showing 31–40 of 164
D.35

Your boiler is struggling to supply enough gas to the burner, likely because it is too cold outside or there is a problem with the gas pipework.

Medium Engineer only £100-£250

Parts commonly replaced

  • Gas valve
  • External gas regulator
  • Inlet pipework

Related codes

D.36

Your boiler is struggling to detect when you turn on your hot taps, meaning you may experience cold water or intermittent temperature changes.

Medium Engineer only £120-£210

Parts commonly replaced

  • Hot water flow sensor (Aqua-Sensor)
  • Wiring harness connecting the sensor

Related codes

D.40

Your boiler is displaying its current target heating temperature rather than a fault code, meaning it is operating as designed.

Low DIY-safe

What to check first

  1. Check if the room thermostat is calling for heat
  2. Monitor the display to see if the status changes as the boiler warms up
  3. Confirm that your heating and hot water are functioning as expected

Related codes

D.41

Your boiler is currently showing you a live reading of the water temperature returning from your radiators rather than indicating a fault.

Low DIY-safe

What to check first

  1. Press the 'i' button to clear the live status information from the display
  2. Monitor the boiler to ensure it transitions back to a standard pressure or temperature reading
  3. Check that your room thermostat is set high enough to call for heat

Related codes

D.44

Your boiler is struggling to detect the flame needed to heat your water or radiators, causing it to shut down for safety.

High Engineer only £120-£320

Parts commonly replaced

  • Ionisation electrode
  • Ignition lead
  • PCB (Printed Circuit Board)

Related codes

D.47

Your boiler's outdoor sensor is struggling to communicate the outside temperature, which means your heating might not adjust correctly to the weather.

Low Engineer only £90-180

Parts commonly replaced

  • External weather compensator sensor
  • Sensor wiring
  • PCB

Related codes

D.50

Your boiler's fan is struggling to run at the correct low speed required for efficient operation.

Medium Engineer only £150-£350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)

Related codes

D.51

Your boiler's computer is reporting an internal memory error regarding how fast the fan should spin, which prevents it from starting up safely.

High Engineer only £280-500

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

D.58

Your boiler is notifying you that it is currently using energy from your solar heating system to pre-heat your water.

Low DIY-safe

What to check first

  1. No action is required as this is an advisory status message rather than a functional fault.
  2. Monitor your hot water temperature to ensure it remains consistent.
  3. If the code persists when solar heating is not active, check your external solar controller settings.

Related codes

D.60

Your boiler has shut down because it is getting too hot and has triggered its safety limit multiple times to prevent damage.

High Engineer only £120-350

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Diverter valve
  • Main heat exchanger

Related codes

Showing 41–50 of 164
D.61

Your boiler has failed to ignite multiple times and has now locked itself out for safety reasons.

High DIY-safe £100-£250

What to check first

  1. Check that your gas prepayment meter has credit
  2. Ensure other gas appliances in your home, like the hob, are working
  3. Press the 'Flame' or 'Reset' button on the boiler control panel once

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PCB (Main Circuit Board)

Related codes

D.64

Your boiler is taking longer than usual to light the flame, which could indicate a minor delay in the starting process.

Low Engineer only £90-250

Parts commonly replaced

  • Ignition Electrodes
  • Lead Set
  • Gas Valve

Related codes

D.65

Your boiler is struggling to light its flame after several attempts and has stopped for safety.

High DIY-safe £120-350

What to check first

  1. Check if your gas meter has credit and the gas emergency control valve is open
  2. Check if other gas appliances in your home, like a hob, are working correctly
  3. Press the 'Reset' button (often indicated by a flame with a cross through it) to restart the ignition process

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Electrode
  • Gas Valve

Related codes

D.67

Your boiler is taking a short, programmed break to prevent the burner from switching on and off too frequently, which protects the internal parts and saves energy.

Low DIY-safe

What to check first

  1. Wait 5 to 15 minutes for the countdown to end naturally
  2. Check that your room thermostat is turned up
  3. Ensure all radiator valves are open to allow heat to dissipate

Related codes

D.68

Your boiler is struggling to light the flame on its first try, which often means it needs more than one attempt to provide you with heating or hot water.

Medium DIY-safe £120-280

What to check first

  1. Check that your gas prepayment meter has credit
  2. Ensure your external gas emergency control valve is fully open
  3. Press the 'Reset' button (flame symbol with a cross) once and wait to see if the error clears

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Ionisation Probe
  • Gas Valve

Related codes

D.69

Your boiler has failed to light the flame twice in a row, meaning it cannot provide heating or hot water until the issue is resolved.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances, like a hob, are working to ensure gas is reaching your home.
  2. Verify that your gas meter has credit and that the emergency control valve is open.
  3. Press the 'Reset' button (indicated by a flame with a line through it) and hold for one second.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ignition Lead

Related codes

D.70

Your boiler is currently stuck in a configuration mode where it is trying to decide whether to send heat to your radiators or your hot water taps.

Medium Engineer only £100-250

Parts commonly replaced

  • Diverter Valve Motor
  • Main PCB

Related codes

D.71

Your boiler is signalling that the heating temperature dial is set to its maximum limit, which is often an advisory message rather than a complete breakdown.

Low DIY-safe £0-80

What to check first

  1. Locate the heating control knob on the front panel (often marked with a radiator icon).
  2. Turn the dial slightly anti-clockwise to a lower setting.
  3. Monitor the boiler to see if the status code clears or updates.

Parts commonly replaced

  • Control knob
  • Potentiometer

Related codes

D.72

Your boiler is continuing to run its internal water pump for a set period after heating your hot water to prevent the unit from getting too hot.

Low DIY-safe £0-120

What to check first

  1. No action is required as this is normal operation
  2. Monitor the boiler for any other actual fault codes
  3. Ensure your thermostat and hot water settings are at desired levels

Parts commonly replaced

  • None (Normal operation)
  • Temperature sensor (NTC)
  • Main PCB

Related codes

D.73

Your boiler is notifying you of an adjustment to the pre-heat temperature used for quicker hot water delivery.

Low DIY-safe £0-60

What to check first

  1. Navigate to the installer level settings in the digital menu
  2. Locate diagnostic code D.73
  3. Adjust the offset value (typically between -15 and +5) to your preferred setting for the warm start feature

Parts commonly replaced

  • None (Software adjustment)

Related codes

Showing 51–60 of 164
D.75

Your boiler is taking too long to heat up the internal hot water storage tank, which often means heat isn't transferring properly.

High Engineer only £150-350

Parts commonly replaced

  • Hot water sensor (NTC)
  • Secondary plate heat exchanger
  • Internal pump

Related codes

D.76

Your boiler is taking a short, programmed break to prevent the burner from switching on and off too frequently, which protects the internal components from unnecessary wear.

Low DIY-safe

What to check first

  1. Wait for approximately 10 to 15 minutes for the countdown to finish
  2. Check that your room thermostat is turned up high enough to call for heat
  3. Ensure radiator valves are open to allow heat to dissipate

Related codes

D.77

Your boiler is limiting the amount of power it uses to heat your hot water, which may lead to it taking longer than usual to reach the desired temperature.

Low Engineer only £90-250

Parts commonly replaced

  • NTC Temperature Sensor
  • PCB
  • Secondary Heat Exchanger

Related codes

D.78

Your boiler is limiting the temperature it uses to heat your hot water, likely because it has detected a measurement error or an overheating risk in the storage cylinder.

Medium Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Cylinder Thermistor
  • Wiring Harness

Related codes

D.80

Your boiler is simply displaying how many hours it has spent providing central heating; this is an information status rather than a fault.

Low DIY-safe

What to check first

  1. Press the 'i' button to exit the information menu
  2. Monitor the display to see if it returns to a standard temperature reading
  3. No further action is required as this is a normal status message

Related codes

D.81

This is just an informational message showing how many hours your boiler has spent providing hot water and does not indicate a fault with your system.

Low DIY-safe

What to check first

  1. Press the 'i' button to return to the standard temperature display
  2. No further action is required as this is a status code, not an error

Related codes

D.82

Your boiler is notifying you that it is currently firing up the burner to begin heating your radiators.

Low DIY-safe

What to check first

  1. Check your thermostat to see if it is calling for heat
  2. Monitor the display to see if the code changes to a temperature reading once the burner starts
  3. No action is required as this is a status message rather than a breakdown fault

Related codes

D.84

Your boiler is simply reminding you that its annual service is due soon and there is no actual fault with the system.

Low Engineer only £80-130

Parts commonly replaced

  • None (Standard Service Items)
  • Burner Gasket
  • Electrode Set

Related codes

D.90

Your boiler's electronic control panel is currently communicating with an external smart thermostat or digital controller to determine how much heat is needed.

Low DIY-safe

What to check first

  1. Check your room thermostat or smart home app to ensure settings are correct
  2. Ensure the batteries in your wireless wall thermostat are not flat
  3. Wait a few minutes, as this is often a normal status message during startup or adjustment

Related codes

Showing 61–70 of 164
D.91

Your boiler's external temperature sensor is communicating its status, but the system is having trouble processing the radio signal correctly.

Low DIY-safe £60-140

What to check first

  1. Check that the batteries in your external outdoor sensor are still working
  2. Ensure there are no large metal objects blocking the signal between the sensor and the boiler
  3. Try resetting the boiler to see if the status clears

Parts commonly replaced

  • External DCF probe sensor
  • DCF receiver module
  • Batteries (if wireless)

Related codes

D.93

Your boiler’s computer is confused because it hasn't been programmed with the correct identity code for this specific model.

High Engineer only £90-180

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

D.96

Your boiler has lost its specific configuration settings and has reverted to its original factory state, meaning it may not communicate correctly with your heating system.

High Engineer only £100-250

Parts commonly replaced

  • Main PCB
  • Display Interface

Related codes

D.97

Your boiler has entered a specialist diagnostic mode usually reserved for engineers to perform advanced testing and setup.

Low DIY-safe £0-80

What to check first

  1. Press the 'i' button to exit the diagnostic mode
  2. Turn the boiler power off at the fused spur switch for 30 seconds
  3. Turn the power back on and wait for the boiler to return to its normal display

Related codes

D.98

Your boiler has detected an internal technical fault that requires an expert to diagnose and reset.

High Engineer only £100-£250

Parts commonly replaced

  • Main PCB
  • Internal wiring harness

Related codes

F.00

Your boiler has lost communication with its internal temperature sensor, preventing it from knowing how hot the water is and causing it to shut down for safety.

High Engineer only £100-£180

Parts commonly replaced

  • Flow NTC thermistor
  • Wiring harness
  • Main PCB

Related codes

F.00 / F.0

Your boiler has lost connection with the internal thermometer that monitors water temperature, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • NTC Flow Sensor
  • Wiring Harness
  • Main PCB

Related codes

F.01

Your boiler has stopped working because a internal sensor that monitors water temperature has lost its electrical connection.

High Engineer only £100-£180

Parts commonly replaced

  • Flow NTC Thermistor
  • NTC Sensor Wiring Harness

Related codes

F.1

Your boiler has failed to ignite and cannot produce heating or hot water because it isn't getting a gas supply or the internal spark is failing.

High DIY-safe £120-280

What to check first

  1. Check if your gas meter has credit (if using a pre-payment meter).
  2. Ensure the gas stopcock valve is fully open.
  3. Try to reset the boiler by pressing the flame/reset button to trigger a new ignition attempt.

Parts commonly replaced

  • Ignition electrode
  • Ignition lead
  • Gas valve
  • PCB

Related codes

F.01 / F.1

Your boiler has stopped working because it cannot properly measure the temperature of the water returning from your radiators.

High Engineer only £120-220

Parts commonly replaced

  • Return temperature sensor (NTC thermistor)
  • Wiring harness / Connector

Related codes

Showing 71–80 of 164
F.4

Your boiler is failing to start because it cannot light the gas needed to create heat.

High DIY-safe £100-£350

What to check first

  1. Check that your gas prepayment meter has credit (if applicable)
  2. Confirm that other gas appliances in your home, like a cooker, are working
  3. Press the 'Flame' or 'Reset' button on the boiler control panel

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ignition Lead
  • Printed Circuit Board (PCB)

Related codes

F.5

Your boiler has shut down because it has reached an unsafe temperature, likely due to water not circulating properly through the system.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Check the boiler pressure is between 1 and 1.5 bar on the gauge
  3. Once the boiler has cooled down, attempt to reset it using the flame/reset button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • NTC Temperature Sensor

Related codes

F.6

Your boiler's internal temperature sensor has stopped working correctly, meaning the system cannot accurately monitor the heat of the water leaving the unit.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC thermistor
  • Wiring harness sensor connector

Related codes

F.10

Your boiler has detected an electrical connection issue with the sensor that monitors the water temperature returning to the unit.

High Engineer only £90-180

Parts commonly replaced

  • NTC Return Sensor
  • Wiring Loom
  • Main PCB

Related codes

F.11

Your boiler has detected that water is failing to circulate through the system, causing the unit to stop working to avoid overheating.

High DIY-safe £90-280

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the blue lever (gas valve) and water isolation valves are in the open position
  3. Check the system pressure and top up to 1.5 bar if it is too low

Parts commonly replaced

  • Circulation pump
  • Internal bypass valve
  • Central heating filter

Related codes

F.12

Your boiler has detected a internal blockage that is preventing water from flowing correctly and affecting the system's pressure.

High Engineer only £120-280

Parts commonly replaced

  • Heat Exchanger
  • Circulation Pump
  • Pipework Seal

Related codes

F.13

Your boiler has detected an electrical short circuit in its internal wiring, likely related to the temperature sensor system.

High Engineer only £120-190

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness
  • Control PCB

Related codes

F.17

Your boiler has detected an electrical wiring issue, or the power supply is not configured correctly, preventing it from starting safely.

High Engineer only £80-180

Parts commonly replaced

  • Main PCB
  • External electrical cabling

Related codes

F.20

Your boiler has reached an unsafe temperature and has automatically shut down to prevent damage.

High DIY-safe £120-300

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate
  2. Ensure there is enough water pressure in the system (typically 1.0 to 1.5 bar on the gauge)
  3. Wait for the boiler to cool down and then press the reset button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • NTC Temperature Sensor

Related codes

F.21

Your boiler has stopped working because the internal burner cannot stay lit or failed to ignite correctly.

High DIY-safe £120-350

What to check first

  1. Check that your gas supply is turned on and other gas appliances are working
  2. Press the 'Reset' button (marked with a flame or 'X') for 3 seconds
  3. Ensure your prepaid gas meter has credit, if applicable

Parts commonly replaced

  • Ignition Electrode
  • Flame Sensing Probe
  • Gas Valve

Related codes

Showing 81–90 of 164
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.

High DIY-safe £0-160

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.
  3. Slowly open the valves until the pressure rises to 1.5 bar, then ensure they are closed tightly.
  4. Press the reset button on the boiler control panel.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

F.23

Your boiler has shut down because the water inside is heating up too quickly or unevenly, likely due to a circulation blockage or a pump issue.

High DIY-safe £150-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar on the gauge
  3. Try resetting the boiler to see if the fault clears

Parts commonly replaced

  • Circulation Pump
  • NTC Temperature Sensors
  • Heat Exchanger (De-scaling)

Related codes

F.24

Your boiler is not circulating enough water through the system, causing it to overheat and shut down for safety.

High DIY-safe £180-350

What to check first

  1. Check if your boiler pressure gauge is between 1.0 and 1.5 bar and top up if low
  2. Ensure all radiator valves are fully open
  3. Bleed your radiators to remove trapped air from the system

Parts commonly replaced

  • Circulating Pump
  • Primary Heat Exchanger
  • Return Filter

Related codes

F.25

Your boiler has shut down because the internal exhaust gases are getting too hot, which is a safety feature to prevent damage or dangerous fumes.

High Engineer only £150-350

Parts commonly replaced

  • Flue gas NTC sensor
  • Heat exchanger (descaling or replacement)
  • Burner seals

Related codes

F.26

Your boiler has stopped working because it cannot properly control the flow of gas needed to stay alight.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Main PCB
  • Wiring harness

Related codes

F.27

Your boiler has detected a flame when there shouldn't be one, which has caused it to shut down for safety purposes.

High Engineer only £150-350

Parts commonly replaced

  • Flame sense electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

F.28

Your boiler is failing to light the gas flame and has locked itself out for safety.

High DIY-safe £120-300

What to check first

  1. Check if your gas meter has credit (if using a prepay meter).
  2. Ensure other gas appliances in your home, like a cooker, are working correctly.
  3. Try to reset the boiler by pressing the flame/reset button once.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB (Control Board)
  • Spark generator

Related codes

F.29

Your boiler was working but the flame has gone out unexpectedly, meaning the system cannot heat your home or water.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances in your home, like a hob, are working to confirm gas supply.
  2. If you have a pre-payment meter, check that you have enough credit.
  3. Press and hold the reset button (usually marked with a flame or cross symbol) for five seconds.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Electrode
  • Condensate Trap or Pipe

Related codes

F.32

Your boiler has detected an issue with the fan that safely pushes waste gases out of your home, causing the system to shut down for safety.

High Engineer only £220-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
F.49

Your boiler's internal communication system has failed, meaning the control panel cannot talk to the parts that heat your water.

High Engineer only £120-350

Parts commonly replaced

  • Main PCB
  • eBUS cable
  • External Controller

Related codes

Showing 91–100 of 164
F.60

Your boiler has detected an internal electrical problem with the gas control system and has shut down as a safety precaution.

High Engineer only £250-450

Parts commonly replaced

  • Gas Valve
  • Main PCB (Printed Circuit Board)
  • Wiring Harness

Related codes

F.61

Your boiler is failing to communicate correctly with the gas valve, meaning it cannot safely manage the fuel needed to provide heating and hot water.

High Engineer only £250-£550

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

F.62

Your boiler has detected a safety issue where the gas valve is not closing properly, meaning gas could still be flowing when it shouldn't be.

Emergency Engineer only £250-450

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

F.63

Your boiler's internal computer brain has suffered a memory failure and can no longer process the instructions needed to operate.

High Engineer only £280-£450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

F.64

Your boiler's internal computer has detected a conflict between its sensors or an electrical fault, causing the system to shut down for safety.

High Engineer only £160-450

Parts commonly replaced

  • NTC Temperature Sensor
  • Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

F.65

Your boiler’s internal control board has become too hot and has shut down as a safety precaution to prevent damage.

High DIY-safe £180-350

What to check first

  1. Turn the boiler off using the main power switch.
  2. Wait for 30 minutes to allow the internal electronics to cool down completely.
  3. Ensure there are no external heat sources near the boiler and turn the power back on.

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Electronic Box Display Unit

Related codes

F.67

Your boiler has detected an internal electrical problem with the system that manages the burner flame, meaning the device cannot safely stay lit.

High Engineer only £250-£450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame Sensing Electrode

Related codes

F.68

Your boiler is struggling to keep a steady flame alight because the gas supply is inconsistent or contains air pockets.

High Engineer only £120-350

Parts commonly replaced

  • Flame sense electrode
  • Gas valve
  • PCB

Related codes

F.70

Your boiler’s control board and display screen are no longer communicating correctly because they haven't been programmed to recognize each other.

High Engineer only £100-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • User Interface/Display

Related codes

F.71

Your boiler's temperature sensor has stuck on a single reading, so the system has shut down because it cannot safely monitor how hot the water is getting.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC thermistor
  • Wiring harness
  • Main PCB

Related codes

Showing 101–110 of 164
F.72

Your boiler has detected an unusual temperature difference between the water leaving the unit and the water returning to it, often caused by a faulty sensor or a circulation blockage.

High Engineer only £120-£250

Parts commonly replaced

  • Flow NTC thermistor
  • Return NTC thermistor
  • Circulation pump

Related codes

F.73

Your boiler's internal sensor can no longer accurately read the water pressure, causing the system to shut down for safety.

High Engineer only £140-£220

Parts commonly replaced

  • Water pressure sensor
  • Sensor wiring harness

Related codes

F.74

Your boiler's internal sensor is struggling to accurately measure the water pressure, which prevents the system from operating safely.

High Engineer only £140-£220

Parts commonly replaced

  • Water Pressure Sensor
  • Sensor Wiring Loom

Related codes

F.75

Your boiler is failing to detect that the pump is moving water, which means it cannot safely heat up and has shut down to protect itself.

High DIY-safe £180-350

What to check first

  1. Check the pressure gauge and ensure it is between 1.0 and 1.5 bar
  2. Use the filling loop to top up the pressure if it is too low
  3. Restart the boiler to see if the pump clears any temporary air locks

Parts commonly replaced

  • Water pressure sensor
  • Central heating pump
  • Expansion vessel

Related codes

F.76

Your boiler has switched itself off because a safety sensor detected that the main heating component has reached an dangerously high temperature.

High Engineer only £250-£650

Parts commonly replaced

  • Thermal fuse
  • Primary Heat Exchanger
  • Overheat Thermostat

Related codes

F.77

Your boiler has detected a problem with the pump that removes waste water or an issue with the flap that controls exhaust gases.

High Engineer only £140-300

Parts commonly replaced

  • Condensate pump
  • Flue non-return flap
  • Wiring harness

Related codes

F.78

Your boiler is struggling to provide hot water correctly because a sensor that monitors water temperature has lost its connection or stopped working.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW temperature sensor (NTC thermistor)
  • Wiring harness
  • External controller link

Related codes

F.83

Your boiler has detected that the temperature sensors aren't tracking heat changes correctly, often because there isn't enough water moving through the system to be measured.

High DIY-safe £100-220

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1.0 and 1.5 bar.
  2. If the pressure is too low, use the filling loop underneath the boiler to top it up to the 1.5 bar mark.
  3. Ensure all radiator valves are fully open to allow water to flow freely.
  4. Press the reset button (usually marked with a flame or 'X') to clear the fault.

Parts commonly replaced

  • NTC Temperature Sensors (Flow/Return)
  • Wiring harness
  • Heat exchanger (if scaled up)

Related codes

F.84

Your boiler has detected that its temperature sensors are giving unusual or conflicting readings, which prevents it from heating up safely.

High Engineer only £120-220

Parts commonly replaced

  • Flow NTC sensor
  • Return NTC sensor
  • Wiring harness

Related codes

F.85

Your boiler has detected that the temperature sensors on the main pipes are either loose, incorrectly installed, or not reading the water flow correctly.

High Engineer only £100-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Flow and Return Thermistors
  • Thermal Paste

Related codes

Showing 111–120 of 164
P.00

Your boiler is currently running a self-cleaning sequence to remove air bubbles from the pipes and internal components.

Low DIY-safe

What to check first

  1. Wait approximately 10 to 15 minutes for the program to complete automatically
  2. Ensure the blue radiator valves or any air vents in the system are open
  3. Check that the system pressure is between 1.0 and 1.5 bar on the gauge

Related codes

P.01

Your boiler has become stuck in a manual testing mode used by engineers and is likely failing to exit this program correctly.

Medium DIY-safe £80-120

What to check first

  1. Turn the boiler power off at the main fused spur switch
  2. Wait for 30 seconds
  3. Turn the power back on to see if the boiler resets to normal operation

Parts commonly replaced

  • Main PCB
  • Control Knobs

Related codes

P.02

Your boiler is currently running a manual test mode to check its performance at the lowest power setting.

Low DIY-safe

What to check first

  1. Wait 15 minutes for the test program to finish automatically
  2. Turn the boiler off at the main power switch and turn it back on to reset the display
  3. Press the 'i' and '+' buttons simultaneously to manually exit the test mode

Related codes

P.06

Your boiler is currently running a self-diagnostic test to help fill and vent air from the system and is not indicating a hardware failure.

Low DIY-safe

What to check first

  1. Wait approximately 15 minutes for the test program to finish automatically
  2. Ensure your radiator valves are open to allow air to circulate and vent
  3. Check that the system pressure is between 1.0 and 1.5 bar on the pressure gauge

Related codes

S.00

Your boiler is working correctly but currently waiting for a command from your thermostat to turn the heating on.

Low DIY-safe £0-£120

What to check first

  1. Check your room thermostat is turned up higher than the current room temperature
  2. Ensure your heating programmer or timer is set to 'ON'
  3. Replace the batteries in your wireless wall thermostat if the screen is blank

Parts commonly replaced

  • Thermostat batteries
  • External room thermostat
  • Mechanical timer

Related codes

S.1

Your boiler is unable to start the heating process because its internal fan, which safely clears waste gases, is failing to spin up properly.

High Engineer only £180-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

S.2

Your boiler has stopped heating up because the water is not being pumped through the system properly.

High DIY-safe £180-350

What to check first

  1. Check that the boiler pressure is between 1.0 and 1.5 bar
  2. Ensure all radiator valves and the boiler's service valves are fully open
  3. Gently bleed air from your radiators using a radiator key

Parts commonly replaced

  • Circulation pump
  • Automatic air vent
  • Pump capacitor

Related codes

S.02

Your boiler is currently preparing to provide heating by running the internal pump to move water through the system.

Low DIY-safe

What to check first

  1. Check that your room thermostat is turned up
  2. Ensure the radiator valves are open
  3. Monitor the display to see if it moves to S.03 or S.04 (normal operation)

Related codes

S.3

Your boiler is struggling to start the burner to provide heating, which means your radiators will not warm up.

High DIY-safe £120-350

What to check first

  1. Check that your gas pre-pay meter has credit
  2. Ensure the gas stop tap is fully open
  3. Press the Reset button (indicated by a flame with a cross through it) and hold for 2 seconds

Parts commonly replaced

  • Ignition Electrode
  • Flame Sense Electrode
  • Gas Valve
  • Ignition Lead

Related codes

Showing 121–130 of 164
S.03

Your boiler is failing to light the gas burner after several attempts, meaning your heating and hot water will not work.

High Engineer only £120-350

Parts commonly replaced

  • Ignition Electrodes
  • Spark Lead
  • Gas Valve
  • PCB

Related codes

S.4

Your boiler is currently firing up to provide central heating, but it has detected a problem with the burner operation.

High Engineer only £120-350

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • Ionisation probe
  • PCB

Related codes

S.04

Your boiler is operating normally and is currently firing up to provide central heating.

Low DIY-safe

What to check first

  1. No action is required as this is a status code, not a fault code.
  2. Ensure your thermostat is set to the desired temperature.
  3. Monitor the display to see if it transitions to other status codes like S.01 or S.03.

Related codes

S.6

Your boiler is failing to settle down correctly after heating your home because the internal fan is running for longer than the system expects.

High Engineer only £120-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

S.06

Your boiler is struggling to clear fumes from the system because the internal fan is running longer than expected during its cooling-down phase.

Medium Engineer only £120-350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

S.7

Your boiler is temporarily finishing its heating cycle by running the pump to cool down, but it has detected that this process isn't working quite as expected.

Medium DIY-safe £100-250

What to check first

  1. Check that at least one radiator (usually the one in the room with the thermostat) has its valves fully open
  2. Ensure the system pressure is between 1.0 and 1.5 bar on the pressure gauge
  3. Press the reset button once to see if the status clears

Parts commonly replaced

  • Circulation Pump
  • Pump Overrun Thermostat
  • Main PCB

Related codes

S.07

Your boiler is staying on longer than usual after central heating use because it is struggling to circulate water and cool itself down properly.

Medium DIY-safe £100-280

What to check first

  1. Ensure all radiator valves (TRVs) are open to allow water to flow
  2. Check if the system pressure is between 1.0 and 1.5 bar
  3. Bleed all radiators to remove trapped air which may be blocking circulation

Parts commonly replaced

  • Circulation Pump
  • Automatic Air Vent
  • Bypass Valve

Related codes

S.8

Your boiler is temporarily in a waiting period to prevent it from cycling on and off too frequently after reaching its target temperature.

Low DIY-safe

What to check first

  1. Wait approximately 5 to 10 minutes for the countdown to end
  2. Check that your room thermostat is turned up higher than the current room temperature
  3. Ensure all radiator valves are fully open to allow heat to dissipate

Related codes

S.08

Your boiler is temporarily resting because it has reached its target temperature and is waiting for a short period before restarting to prevent unnecessary wear.

Low DIY-safe

What to check first

  1. Check if your room thermostat is set to the desired temperature
  2. Wait approximately 15 to 30 minutes for the countdown to end
  3. Ensure radiators are turned on to allow heat to dissipate

Related codes

Showing 131–140 of 164
S.11

Your boiler is trying to provide hot water, but the internal fan is failing to start up properly to clear the system.

High Engineer only £180-450

Parts commonly replaced

  • Fan Assembly
  • Air Pressure Switch
  • PCB

Related codes

S.14

Your boiler has detected a request for hot water but the air flow sensor is not responding correctly, preventing the system from firing up.

High Engineer only £140-£280

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Main PCB

Related codes

S.15

Your boiler is briefly keeping the pump and fan running to cool itself down after you have finished using the hot water.

Low DIY-safe

What to check first

  1. No action is required as this is a normal operating status and not a fault.
  2. Wait a few minutes for the status code to change once the cooling cycle is complete.
  3. If the code never disappears, try resetting the boiler once.

Related codes

S.16

Your boiler is failing to switch off the fan after providing hot water, which is preventing it from starting the next heating cycle.

High Engineer only £150-350

Parts commonly replaced

  • Air pressure switch
  • Main PCB
  • Fan assembly

Related codes

S.17

Your boiler is struggling to circulate water after you have used the hot water tap, which is often caused by a blockage or a valve that is stuck.

Medium Engineer only £120-£280

Parts commonly replaced

  • Diverter Valve
  • Internal Circulation Pump
  • Main Heat Exchanger

Related codes

S.21

Your boiler is trying to provide hot water but cannot safely start the fan required to clear exhaust fumes.

High Engineer only £180-450

Parts commonly replaced

  • Fan Assembly
  • Air Pressure Switch
  • Printed Circuit Board (PCB)

Related codes

S.22

Your boiler has detected that hot water isn't moving through the system correctly, which is preventing it from heating up your taps.

High Engineer only £180-350

Parts commonly replaced

  • Secondary heat exchanger
  • Diverter valve
  • Internal pump

Related codes

S.23

Your boiler is failing to light the burner when you turn on your hot water tap.

High Engineer only £120-£350

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • DHW Flow Sensor
  • Flame Sensing Electrode

Related codes

S.24

Your boiler is currently working as it should by firing up the burner to heat your hot water.

Low DIY-safe

What to check first

  1. No action required
  2. Monitor for any future error codes starting with 'F'
  3. Ensure your hot water taps are closed if you do not expect the boiler to be running

Related codes

Showing 141–150 of 164
S.25

Your boiler is staying in its cooling-down phase for too long after you have finished using hot water.

Medium Engineer only £120-280

Parts commonly replaced

  • Flow sensor
  • Diverter valve
  • Main PCB

Related codes

S.27

Your boiler is briefly running the internal pump after you have finished using hot water to safely cool down the heat exchanger.

Low DIY-safe
S.28

Your boiler is taking a short, programmed break to prevent the burner from turning on and off too frequently while heating your water.

Low DIY-safe

What to check first

  1. Wait approximately 5 to 10 minutes for the internal timer to expire
  2. Ensure hot water taps are fully turned off during this period
  3. Check that your digital programmer or thermostat is calling for heat correctly

Related codes

S.30

Your wall thermostat has told the boiler to stay off, likely because the room is already warm enough or the thermostat timer is set to an 'off' period.

Low DIY-safe £0-120

What to check first

  1. Check if your wall thermostat is set to a temperature higher than the current room temperature.
  2. Verify that the timer or programmer is set to 'ON' or 'AUTO' mode.
  3. If your thermostat is battery-powered, try replacing the batteries with fresh ones.

Parts commonly replaced

  • Thermostat batteries
  • Room thermostat
  • External programmer

Related codes

S.31

Your boiler is currently set to summer mode, which means it is providing hot water but has intentionally turned off the central heating functions.

Low DIY-safe

What to check first

  1. Locate the heating temperature control knob on the boiler front panel.
  2. Turn the knob clockwise away from the 'Sun' icon or leftmost position to a higher setting.
  3. Check if your external room thermostat or programmer is set to 'On' or 'Auto' and calling for heat.

Related codes

S.32

Your boiler has temporarily stopped because the fan, which clears exhaust gases, isn't spinning at the correct speed.

Medium Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Air pressure switch

Related codes

S.34

Your boiler has paused operation because it believes the internal temperature has dropped low enough to risk freezing the pipework.

Medium DIY-safe £0-120

What to check first

  1. Check that your main thermostat or programmer is turned up
  2. Ensure the boiler's power supply has not been switched off externally
  3. Slightly increase the room temperature to help the system warm up naturally

Parts commonly replaced

  • NTC Temperature Sensor
  • PCB (Printed Circuit Board)

Related codes

S.36

Your boiler has received a signal from your thermostat or internal settings saying that heat is not currently required, so it is staying in standby mode.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature.
  2. Ensure your heating programmer or timer is set to 'On' or 'Auto'.
  3. Replace the batteries in your wireless wall thermostat if the screen is blank or fading.

Parts commonly replaced

  • Thermostat batteries
  • External Room Thermostat
  • Low voltage wiring

Related codes

S.39

Your boiler has paused its heating process because an external safety switch, usually linked to your condensate pump or an overheat sensor, has tripped.

High DIY-safe £90-250

What to check first

  1. Check if the condensate pump tank is full or blocked.
  2. Ensure the pump is plugged in and turned on.
  3. Check for any obvious leaks or blockages in the white plastic discharge pipe.
  4. Restart the boiler to see if the status clears.

Parts commonly replaced

  • Condensate pump
  • Contact thermostat
  • Wiring harness

Related codes

Showing 151–160 of 164
S.40

Your boiler is currently running at a lower power level because it has detected a minor internal issue and is protecting itself from damage while still trying to provide some heat.

Low DIY-safe £90-250

What to check first

  1. Check that your radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Press the reset button (flame symbol) to see if the status clears

Parts commonly replaced

  • NTC Temperature Sensor
  • Water Pressure Sensor

Related codes

S.41

Your boiler has too much water inside it, causing the internal pressure to rise to an unsafe level.

High DIY-safe £80-220

What to check first

  1. Check that the filling loop valves are fully closed and not letting in water.
  2. Locate a radiator and bleed water from the air vent into a jug to reduce system pressure.
  3. Monitor the pressure gauge on the boiler until it returns to between 1.0 and 1.5 bar.
  4. Restart the boiler to clear the status code.

Parts commonly replaced

  • Expansion Vessel
  • Filling Loop Valve
  • Pressure Relief Valve (PRV)

Related codes

S.42

Your boiler has paused because a safety flap in the flue system is stuck or sending an incorrect signal, preventing the exhaust gases from leaving safely.

High Engineer only £120-280

Parts commonly replaced

  • Flue non-return flap
  • Exhaust sensor
  • Fan assembly

Related codes

S.46

Your boiler is struggling to keep its pilot flame alight when running at its lowest setting, meaning it may stop working when it tries to save energy.

Medium Engineer only £120-280

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Burner assembly

Related codes

S.53

Your boiler has temporarily stopped working because it cannot move water around the system fast enough, likely due to a blockage or a pump issue.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves (TRVs) are fully open
  2. Check the boiler pressure gauge and top up to 1.5 bar if low
  3. Ensure all bypass or isolation valves underneath the boiler are in the open position

Parts commonly replaced

  • Circulating Pump
  • Main Heat Exchanger (Cleaning)
  • Flow/Return Thermistors

Related codes

S.54

Your boiler has temporarily paused operation because it has detected a lack of water circulation or a rapid rise in temperature that could lead to overheating.

High DIY-safe £100-350

What to check first

  1. Check that your boiler pressure gauge is between 1.0 and 1.5 bar
  2. Ensure all radiator valves and internal bypass valves are fully open
  3. Bleed all radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulation pump
  • NTC Temperature Sensors
  • Main Heat Exchanger (Flushing)

Related codes

S.57

Your boiler has temporarily paused operation to prevent overheating and should restart automatically once the internal sensor detects a safe temperature.

Low DIY-safe £0-120

What to check first

  1. Monitor the boiler for a few minutes as it should restart automatically
  2. Check that at least one radiator or bypass valve is open to allow heat dissipation
  3. If the code persists, ensure the system pressure is between 1 and 1.5 bar
  4. Press the reset button if the boiler enters a full lockout mode

Parts commonly replaced

  • NTC Temperature Sensor
  • Heat Exchanger (cleaning)

Related codes

S.58

Your boiler is temporarily limiting its power because the burner's flame is being disturbed by external wind or internal air flow issues.

Low Engineer only £90-180

Parts commonly replaced

  • Gas valve (calibration)
  • Flue seals
  • Burner door seal

Related codes

S.61

Your boiler has failed an automatic check to identify the type of gas being supplied, which has caused it to stop running for safety reasons.

High Engineer only £180-450

Parts commonly replaced

  • Gas valve
  • Printed Circuit Board (PCB)
  • Ionisation electrode

Related codes

S.85

Your boiler is struggling to move enough water through the system, which is causing it to work harder than it should.

Medium DIY-safe £120-280

What to check first

  1. Check that your radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Bleed your radiators to remove any trapped air

Parts commonly replaced

  • Circulation Pump
  • Bypass Valve
  • Main Heat Exchanger (Descaling)

Related codes

Showing 161–164 of 164
S.96

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, causing it to stop running for safety.

High Engineer only £120-190

Parts commonly replaced

  • Return NTC thermistor
  • Connecting wiring harness

Related codes

S.98

Your boiler is temporarily pausing because it has noticed an unusual difference in temperature readings and needs to double-check its internal sensors before starting up again.

Medium Engineer only £120-250

Parts commonly replaced

  • Flow NTC sensor
  • Return NTC sensor
  • Main PCB

Related codes

S.O

Your boiler is currently idle because it has not received a signal from your thermostat or timer to turn the heating on.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature
  2. Ensure your heating programmer or timer is set to an 'ON' period
  3. Replace the batteries in your wireless thermostat if the screen is blank

Parts commonly replaced

  • Room thermostat
  • Receiver box
  • Batteries

Related codes

S13

Your boiler is failing to light the flame when you turn on your hot water taps.

High Engineer only £120-£250

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Electrode
  • PCB

Related codes