Vaillant Turbomax Plus 828 Fault codes & diagnostics

26 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

Download the Vaillant Turbomax Plus 828 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 25 High
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 26 documented codes

Tap any card for details

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
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
Showing 11–20 of 26
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
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
Showing 21–26 of 26
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 main control unit has detected an internal communication failure, meaning it cannot safely operate the system.

High Engineer only £250-450

Parts commonly replaced

  • Main printed circuit board (PCB)

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
Status & diagnostic codes

66 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

d.00 Diagnostic Your boiler is currently operating in a temporary diagnostic mode used by engineers to check its performance, rather than a standard system error. d.01 Diagnostic Your boiler is currently running its internal pump to safely circulate leftover heat, which is a normal part of the shutdown process. d.02 Diagnostic Your boiler is currently in a brief, normal cooling-down period and will restart automatically once the temperature drops. d.05 Diagnostic This code is simply showing you the current temperature setting for your heating water rather than indicating a fault with your boiler. d.07 Diagnostic Your boiler is signalling an issue with the sensor that monitors the 'warm start' function, which is the feature that keeps your water hot for instant access. d.08 Diagnostic Your boiler is currently idle because it is not receiving a signal from your thermostat or timer to turn on the heating or hot water. d.10 Diagnostic This is a status code indicating that your boiler's internal water pump is currently switched off. d.11 Diagnostic Your boiler is currently monitoring the status of an external pump connected to your heating system to ensure water is flowing correctly. d.21 Diagnostic Your boiler is failing to detect the flame that it is trying to light, which has caused it to shut down for your safety. D.22 Diagnostic Your boiler is currently reporting that there is not enough water pressure inside the system to operate safely. d.23 Diagnostic Your boiler is currently set to summer mode, which means it is configured to only provide hot water and will not turn on your radiators. D.24 Diagnostic 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. d.25 Diagnostic This code is simply an information display showing whether your boiler's 'warm start' feature—which keeps a small amount of water hot for instant delivery—is currently turned on or off. d.30 Diagnostic Your boiler is struggling to signal that it is ready to release gas for the burner, which is preventing it from heating your water or home. d.33 Diagnostic Your boiler has detected that the internal fan responsible for venting exhaust gases is not spinning at the correct speed to operate safely. d.34 Diagnostic Your boiler is struggling to confirm that the fan, which manages the safe removal of exhaust gases, is spinning at the correct speed. d.35 Diagnostic Your boiler is struggling to switch between heating your radiators and providing hot water to your taps, which means you may have no heating or hot water at the moment. d.37 Diagnostic Your boiler is having difficulty communicating with the part that controls the gas flow for your heating and hot water. d.40 Diagnostic Your boiler is simply displaying the current temperature of the water flowing through your heating system, and this is a normal operating status rather than an error. d.41 Diagnostic Your boiler is simply displaying a live temperature reading from its internal return pipe, which is an informational status update rather than an error or a fault. d.50 Diagnostic Your boiler is simply reporting that the water inside the heating system has reached its maximum permitted temperature, meaning it has temporarily stopped heating to prevent overheating. d.60 Diagnostic Your boiler has detected that it is getting too hot and has automatically shut itself down to prevent damage. d.61 Diagnostic Your boiler has logged several attempts to start that failed, causing it to shut down for safety. d.64 Diagnostic Your boiler is noting how long it takes to light the flame, which is a background diagnostic reading rather than an active fault stopping your heating or hot water. d.65 Diagnostic Your boiler is failing to light because it cannot detect a flame within the time limit allowed, which usually suggests a problem with the gas supply or the ignition process. d.67 Diagnostic Your boiler is currently in a temporary cooling-down period and will restart automatically once it reaches the correct temperature. d.68 Diagnostic Your boiler has failed to start the fire needed to heat your water multiple times and has now paused for safety. d.69 Diagnostic Your boiler has failed to start up after repeated attempts, meaning it is currently unable to provide heating or hot water safely. d.71 Diagnostic Your boiler is simply displaying a configuration setting that tells you the maximum temperature your heating system is allowed to reach. d.72 Diagnostic Your boiler is simply performing a routine internal check to ensure the water inside is being circulated correctly, which is a normal part of its operation. d.73 Diagnostic Your boiler is displaying a diagnostic setting for its 'warm start' feature, which controls how quickly hot water reaches your taps. d.75 Diagnostic Your boiler has spent too long trying to heat your hot water and has automatically timed out to prevent the system from overheating. d.76 Diagnostic Your boiler is displaying a configuration message indicating it is attempting to verify the type of gas supply it is currently using. d.80 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your home, rather than indicating a fault. d.81 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your hot water, rather than indicating a fault. d.82 Diagnostic This code is simply an information display showing how many times your boiler has turned on to heat your home, rather than an indication of a fault. d.83 Diagnostic This code is simply an information log showing how many times your hot water system has started up, rather than an indication of a fault. S.00 Status Your boiler is currently waiting for a signal from your thermostat or timer to tell it to turn the heating on. S.01 Status 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. S.02 Status Your boiler is currently preparing to start the heating process and is performing a routine initial check by running the pump. S.03 Status Your boiler is currently trying to light the flame to start your central heating. S.04 Status Your boiler is currently working as normal and is simply heating up the radiators in your home. S.05 Status Your boiler is temporarily cooling itself down after use and should return to normal operation shortly. S.07 Status Your boiler is briefly keeping the pump running after heating to safely circulate and dissipate leftover heat from the system. S.08 Status 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. S.10 Status Your boiler is simply letting you know that it is currently busy heating up water for your taps or shower. S.11 Status Your boiler is currently preparing to provide hot water and is performing a routine check of its internal fan. S.13 Status Your boiler is currently trying to light the flame to provide hot water, but it has not quite finished the process yet. S.14 Status Your boiler has successfully lit the burner to provide hot water and is working exactly as it should. S.16 Status 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. S.17 Status Your boiler is temporarily running the pump to cool itself down after you have used the hot water. S.20 Status Your boiler is temporarily pre-heating its internal water tank to ensure you get hot water quickly when you turn on the tap. S.21 Status Your boiler is currently warming up its internal components to make sure hot water is available quickly when you turn on the tap. S.23 Status Your boiler is currently preparing itself for a warm start to ensure you have hot water quickly when you turn the tap on. S.24 Status 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. S.27 Status 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. S.28 Status 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. S.30 Status Your boiler is working fine, but your thermostat or external timer is currently telling it not to turn the heating on. S.31 Status Your boiler is currently set to 'Summer Mode', which means the central heating is turned off and it will only provide hot water. S.32 Status Your boiler has paused because the fan is not spinning at the correct speed, preventing it from safely clearing waste gases. S.33 Status Your boiler has paused because it cannot confirm that waste gases are being safely cleared through the flue pipe. S.34 Status Your boiler has detected that the temperature is too cold and is running automatically to prevent the internal pipes from freezing. S.36 Status 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. S.39 Status Your boiler has paused because a safety sensor detected that the water temperature is too high for your underfloor heating system. S.53 Status Your boiler has temporarily paused operation because it is struggling to circulate enough water to safely carry heat away from the burner. S.54 Status 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.