Vaillant Turbomax Plus 828 Fault codes & diagnostics

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

Combi Natural Gas 28 kW 2000-2005 Discontinued

Replaced by: ecoMAX

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 30 High 3 Medium 24 Low
Just want the most common Vaillant Turbomax Plus 828 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 58 documented codes

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D.22

Your boiler is currently reporting that there is not enough water pressure inside the system to operate safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually two silver braided hoses with small valves) underneath the boiler.
  2. Open both valves slowly until you hear water flowing and the pressure gauge on the front of the boiler reaches between 1.0 and 1.5 bar.
  3. Close both valves tightly and reset the boiler.

Parts commonly replaced

  • Filling loop
  • Expansion vessel recharge
  • Pressure sensor

Related codes

Full explanation for D.22
D.24

Your boiler is struggling to operate because external controls like your thermostat or timer are sending conflicting signals or aren't communicating correctly with the main unit.

Medium DIY-safe £60-140

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature.
  2. Replace the batteries in your wireless wall thermostat or programmer.
  3. Ensure your external timer or smart hub is switched on and has a stable connection.

Parts commonly replaced

  • Room thermostat
  • External programmer
  • Receiver unit

Related codes

Full explanation for D.24
F 22

Your boiler has stopped working because the water pressure is too low for the system to run safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually two silver braided hoses with small valves under the boiler).
  2. Slowly open both valves to allow water into the system.
  3. Watch the pressure gauge and close the valves tightly once it reaches 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for F 22
F.00

Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit due to a sensor or wiring fault.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC thermistor
  • Wiring harness connector

Related codes

Full explanation for F.00
F.01

Your boiler has stopped working because one of its internal temperature sensors is not communicating correctly with the main control board.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC thermistor
  • NTC wiring harness

Related codes

Full explanation for F.01
F.10

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit, causing it to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flow NTC Thermistor
  • Wiring Harness
  • NTC Sensor Clip

Related codes

Full explanation for F.10
F.11

Your boiler has detected an electrical fault with the sensor that monitors water temperature returning to the unit, causing it to stop heating for safety.

High Engineer only £120-£200

Parts commonly replaced

  • Return NTC thermistor
  • Wiring harness
  • NTC sensor clip

Related codes

Full explanation for F.11
F.20

Your boiler has sensed it is getting too hot and has shut itself down as a safety precaution.

High DIY-safe £120-350

What to check first

  1. Check that your radiator valves are open to allow water to circulate.
  2. Ensure there is enough water pressure in the system (typically 1 to 1.5 bar).
  3. Wait for the boiler to cool down and press the reset button (flame symbol with a cross).

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Heat exchanger (flushing debris)

Related codes

Full explanation for F.20
F.22

Your boiler has detected that there is not enough water inside the system to operate safely, forcing it to shut down to prevent damage.

High DIY-safe £120-350

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 filling loop (usually two braided hoses or blue handles) underneath the boiler.
  3. Slowly open the valves to let water into the system until the gauge reaches 1.2 bar, then ensure they are closed tightly.
  4. Press the 'Flame/Cross' button to reset the boiler.

Parts commonly replaced

  • Circulation Pump
  • Water Pressure Sensor
  • Automatic Air Vent

Related codes

Full explanation for F.22
F.23

Your boiler has detected that water isn't moving through the system properly, causing it to heat up too quickly and shut down to prevent damage.

High DIY-safe £150-£350

What to check first

  1. Check that your radiator valves are open
  2. Ensure the boiler pressure gauge is between 1.0 and 1.5 bar
  3. Gently bleed all radiators to remove trapped air
  4. Reset the boiler using the flame symbol button

Parts commonly replaced

  • Circulation Pump
  • Flow/Return NTC Sensors
  • Pump Capacitor

Related codes

Full explanation for F.23
Showing 11–20 of 58
F.24

Your boiler is heating up too quickly because the water isn't moving through the system properly, often caused by trapped air or a stuck pump.

High DIY-safe £100-£350

What to check first

  1. Check that your boiler pressure is between 1.0 and 1.5 bar on the pressure gauge
  2. Bleed all radiators to remove trapped air from the system
  3. Ensure all radiator valves and isolation valves under the boiler are fully open
  4. Try resetting the boiler using the button with the flame/cross symbol

Parts commonly replaced

  • Circulating Pump
  • Flow/Return NTC Thermistor
  • Automatic Air Vent

Related codes

Full explanation for F.24
F.27

Your boiler has detected a flame when there shouldn't be one, which usually means the internal electronics or the gas valve are malfunctioning.

High Engineer only £180-450

Parts commonly replaced

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

Related codes

Full explanation for F.27
F.28

Your boiler is failing to light the flame after three attempts, which is usually caused by a gas supply issue or a component failure in the ignition system.

High DIY-safe £120-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to ensure gas is reaching your home.
  2. Check if your prepaid gas meter (if applicable) has credit.
  3. Try resetting the boiler by pressing the flame symbol button or the reset button on the front panel.

Parts commonly replaced

  • Gas valve
  • Ignition electrodes
  • Electronic igniter unit
  • Ignition lead

Related codes

Full explanation for F.28
F.29

Your boiler has lost its flame while running and cannot manage to relight itself, meaning it has stopped providing heating and hot water.

High DIY-safe £100-350

What to check first

  1. Check that your gas emergency control valve is open and other gas appliances like your hob are working.
  2. If you have a prepaid gas meter, verify that you have sufficient credit.
  3. Press the reset button (represented by a flame symbol with a cross) for one second.

Parts commonly replaced

  • Gas Valve
  • Ignition Electrode
  • Flame Sensing Electrode
  • Condensate Trap (if blocked)

Related codes

Full explanation for F.29
F.32

Your boiler has stopped working because the fan is not spinning at the correct speed, preventing it from clearing exhaust gases safely.

High Engineer only £180-450

Parts commonly replaced

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

Related codes

Full explanation for F.32
F.33

Your boiler has stopped working because the safety sensor that monitors the exhaust fumes is not detecting the correct airflow.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube

Related codes

Full explanation for F.33
F.37

Your boiler has detected a problem with how the internal fan is spinning, which means it cannot safely vent exhaust fumes and has shut down as a precaution.

High Engineer only £180-450

Parts commonly replaced

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

Related codes

Full explanation for F.37
F.41

Your boiler has lost its electronic configuration and no longer knows which type of gas it should be burning to operate safely.

High Engineer only £80-140

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for F.41
F.42

Your boiler has detected an internal wiring problem or a connection issue that is preventing the control board from communicating properly.

High Engineer only £120-280

Parts commonly replaced

  • Wiring harness (cable loom)
  • PCB (Main Control Board)

Related codes

Full explanation for F.42
F.43

Your boiler has stopped working because its internal electrical wiring has developed a fault or is disconnected.

High Engineer only £120-£280

Parts commonly replaced

  • Main wiring harness
  • Low voltage cable loom
  • PCB connector

Related codes

Full explanation for F.43
Showing 21–30 of 58
F.60

Your boiler's main internal computer has developed a technical fault and can no longer control the heating and hot water safely.

High Engineer only £250-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for F.60
F.62

Your boiler is still detecting a flame for a short time after it has been told to turn off, which is a safety concern that requires an engineer.

Emergency Engineer only £180-450

Parts commonly replaced

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

Related codes

Full explanation for F.62
F.63

Your boiler's internal computer has developed an electrical communication error and can no longer control the heating process safely.

High Engineer only £250-£450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for F.63
F.64

Your boiler has detected a communication error between its internal sensors and the main control board, preventing it from heating your water safely.

High Engineer only £120-£450

Parts commonly replaced

  • Flow or Return NTC Thermistor
  • Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for F.64
F.65

Your boiler's internal computer is overheating, which has caused the system to shut down to prevent damage to the electronics.

High Engineer only £280-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Loom

Related codes

Full explanation for F.65
F.66

Your boiler is having trouble communicating with its control screen, which means you cannot see or adjust your heating settings.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB
  • LCD Display Board
  • Ribbon Cable

Related codes

Full explanation for F.66
F.67

Your boiler's main control board has detected an internal electronic error and can no longer communicate with the system's sensors correctly.

High Engineer only £280-£450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wire harness Loom

Related codes

Full explanation for F.67
S.00

Your boiler is currently waiting for a signal from your thermostat or timer to tell it 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 programmer or timer is set to an 'ON' period.
  3. Replace the batteries in your wireless room thermostat if the screen is blank.

Parts commonly replaced

  • Room thermostat
  • Receiver box
  • External programmer

Related codes

Full explanation for S.00
S.01

Your boiler is currently preparing its internal fan to start the heating process and this is a normal status message rather than an actual error.

Low DIY-safe

What to check first

  1. Check that your room thermostat or programmer is calling for heat
  2. Wait 2-3 minutes to see if the status changes to a heating sequence
  3. Ensure there is a demand for heating and that radiator valves are open

Related codes

Full explanation for S.01
Showing 31–40 of 58
S.05

Your boiler is temporarily cooling itself down after use and should return to normal operation shortly.

Low DIY-safe

What to check first

  1. Wait for 5 to 10 minutes for the cooling cycle to complete
  2. Ensure your radiator valves are open to allow heat to dissipate
  3. If the code persists for hours, try resetting the boiler

Related codes

Full explanation for S.05
S.07

Your boiler is briefly keeping the pump running after heating to safely circulate and dissipate leftover heat from the system.

Low DIY-safe

Related codes

Full explanation for S.07
S.08

Your boiler has reached its required temperature and has temporarily paused to prevent it from switching on and off too frequently, which protects the internal components and saves energy.

Low DIY-safe

What to check first

  1. Wait up to 15 minutes for the 'anti-cycling' timer to finish; the boiler will restart automatically.
  2. Check that your room thermostat is turned up higher than the current room temperature.
  3. Ensure your radiator valves are open to allow the heat to dissipate effectively.

Related codes

Full explanation for S.08
S.13

Your boiler is currently trying to light the flame to provide hot water, but it has not quite finished the process yet.

Low DIY-safe £0-120

What to check first

  1. Check if hot water is being delivered to your taps
  2. Monitor the display to see if it changes to a heating code (e.g. S.14)
  3. No action is required as this is a normal status message

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Generator

Related codes

Full explanation for S.13
Showing 41–50 of 58
S.16

Your boiler is continuing to run the fan for a short period after you have finished using hot water to help the unit cool down safely.

Low DIY-safe

What to check first

  1. No action is required as this is a normal operating status and not a fault
  2. Ensure hot water taps are fully closed
  3. Monitor the display to see if it changes back to a heating or standby code after a few minutes

Related codes

Full explanation for S.16
S.17

Your boiler is temporarily running the pump to cool itself down after you have used the hot water.

Low DIY-safe

What to check first

  1. Wait for the code to clear automatically as it is a normal status message
  2. Ensure your radiator valves (TRVs) are open to allow heat dissipation
  3. Check that the boiler pressure is between 1 and 1.5 bar on the gauge

Related codes

Full explanation for S.17
S.20

Your boiler is temporarily pre-heating its internal water tank to ensure you get hot water quickly when you turn on the tap.

Low DIY-safe

What to check first

  1. No action is required as this is a normal operational status message.
  2. If you wish to stop this from happening, turn the 'Comfort' or 'Warmstart' dial to the 'off' position.
  3. Check your user manual to see how to disable the pre-heat function if you prefer to save energy.

Related codes

Full explanation for S.20
S.21

Your boiler is currently warming up its internal components to make sure hot water is available quickly when you turn on the tap.

Low DIY-safe

What to check first

  1. Check if your hot water is working as normal
  2. Identify if the 'Warm Start' function is enabled (often a small LED or dial setting)
  3. Turn off the Warm Start function if you wish to save energy and stop the fan from running periodically

Related codes

Full explanation for S.21
S.23

Your boiler is currently preparing itself for a warm start to ensure you have hot water quickly when you turn the tap on.

Low DIY-safe

What to check first

  1. No action is required as this is a normal status code, not a fault.
  2. If you wish to stop the boiler from pre-heating, you can turn off the comfort/warm start function using the control dial.
  3. Ensure your thermostat is set to the desired temperature if you have no heating.

Related codes

Full explanation for S.23
S.24

Your boiler is briefly firing up to pre-heat its internal water supply so that you get hot water more quickly when you turn the tap on.

Low DIY-safe

What to check first

  1. Locate the right-hand control knob on the boiler fascia
  2. Turn the knob fully anticlockwise to the 'Off' position to disable the pre-heat feature
  3. Observe if the 'S.24' code disappears and only returns when hot water is requested

Related codes

Full explanation for S.24
S.27

Your boiler is briefly running its internal pump after a demand for hot water to safely dissipate excess heat and keep the system ready for use.

Low DIY-safe

Related codes

Full explanation for S.27
S.28

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

Low DIY-safe

What to check first

  1. Wait up to 15 minutes for the timer to count down
  2. Check that your room thermostat is turned up high enough to call for heat
  3. Ensure the pre-heat (Warm Start) function is not set to a temperature much higher than your actual needs

Related codes

Full explanation for S.28
S.30

Your boiler is working fine, but your thermostat or external timer is currently telling it not 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 'ON' or 'AUTO'.
  3. Replace the batteries in your wireless room thermostat if the screen is blank or fading.

Parts commonly replaced

  • Thermostat batteries
  • Room thermostat
  • Heating programmer

Related codes

Full explanation for S.30
S.31

Your boiler is currently set to 'Summer Mode', which means the central heating is turned off and it will only provide hot water.

Low DIY-safe

What to check first

  1. Locate the heating control knob on the boiler control panel (usually the one with a radiator icon).
  2. Turn the knob clockwise to your desired temperature setting.
  3. The 'S.31' code should disappear as the boiler switches back into heating mode.

Related codes

Full explanation for S.31
Showing 51–58 of 58
S.32

Your boiler has paused because the fan is not spinning at the correct speed, preventing it from safely clearing waste gases.

High Engineer only £180-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Venturi tube

Related codes

Full explanation for S.32
S.33

Your boiler has paused because it cannot confirm that waste gases are being safely cleared through the flue pipe.

High Engineer only £100-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan
  • Venturi Tube

Related codes

Full explanation for S.33
S.34

Your boiler has detected that the temperature is too cold and is running automatically to prevent the internal pipes from freezing.

Low DIY-safe £0-60

What to check first

  1. Wait for the boiler to finish its warming cycle once the temperature rises
  2. Ensure your home thermostat is turned up to a normal heating level
  3. Open any radiator valves in cold rooms to allow circulation
  4. Check that the condensate pipe outside hasn't frozen

Related codes

Full explanation for S.34
S.36

Your boiler is waiting for a signal from your thermostat or programmer, but it isn't receiving one, so it is staying in standby mode.

Medium DIY-safe £60-180

What to check first

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

Parts commonly replaced

  • Room thermostat
  • Programmable timer
  • Thermostat batteries

Related codes

Full explanation for S.36
S.39

Your boiler has paused because a safety sensor detected that the water temperature is too high for your underfloor heating system.

High Engineer only £90-180

Parts commonly replaced

  • Limit Thermostat
  • Underfloor Heating Pump
  • Mixing Valve

Related codes

Full explanation for S.39
S.52

Your boiler is currently trying to light the flame and is at a normal stage in the starting sequence, though a delay here often points to a minor issue with the gas flow or the ignition components.

Low Engineer only £100-250

Parts commonly replaced

  • Ignition electrodes
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for S.52
S.53

Your boiler has temporarily paused operation because it is struggling to circulate enough water to safely carry heat away from the burner.

High DIY-safe £100-£280

What to check first

  1. Check the pressure gauge on the front of the boiler and ensure it is between 1.0 and 1.5 bar.
  2. If the pressure is low, use the filling loop valves underneath the boiler to top up the water level.
  3. Ensure all radiator valves are fully open to allow water to flow freely through the system.

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger (Cleaning/Descaling)
  • Pressure Sensor

Related codes

Full explanation for S.53
S.54

Your boiler has paused because it is heating up much more quickly than it should, suggesting that water isn't moving through the system properly.

Medium DIY-safe £100-£350

What to check first

  1. Check that all radiator valves and internal bypass valves are fully open
  2. Check the boiler pressure gauge and top up to 1.5 bar if it is low
  3. Bleed any trapped air from your radiators

Parts commonly replaced

  • Central heating pump
  • Primary heat exchanger (de-scaling)
  • Flow/Return thermistors

Related codes

Full explanation for S.54