Vaillant ecoTEC Plus 832 Fault codes & diagnostics

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

Combi Natural Gas 28 kW 2017 onwards Discontinued
GC Number 47-044-84

Replaced by: ecoTEC Plus 832 (New Generation)

Download the Vaillant ecoTEC Plus 832 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
12 Emergency 85 High 11 Medium 2 Low

Which version do you have?

The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.

GC number Appliance (register name) Produced
47-044-84 ecoTEC plus 832 VUW 246/5-5 (H-GB) R6 2017–present

All 110 documented codes

Tap any card for details

con

Your boiler's control panel and its internal computer are not talking to each other, meaning the unit cannot receive instructions to provide heat or hot water.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB
  • Display Interface Module
  • Wiring harness

Related codes

F.000

Your boiler has lost the ability to accurately measure the temperature of the water flowing through it, so it has shut down to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • NTC flow temperature sensor
  • Wiring harness

Related codes

F.001

Your boiler has lost its connection to a sensor that measures the temperature of water returning from your radiators, so it has safely shut down to prevent damage.

High Engineer only £120-220

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.002

Your boiler is struggling to detect the temperature of the water it is heating, which means it has stopped providing hot water to your taps.

High Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

F.003

Your boiler is struggling to detect the temperature of your hot water cylinder, which means it may not be heating your water correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder NTC sensor
  • Wiring harness

Related codes

F.010

Your boiler has lost the ability to measure the temperature of the water flowing through the system, so it has safely shut down to prevent overheating.

High Engineer only £120-200

Parts commonly replaced

  • NTC Flow Temperature Sensor
  • Wiring harness

Related codes

F.011

Your boiler is struggling to read the temperature of the water returning to it, which prevents the system from heating your home correctly.

High Engineer only £120-220

Parts commonly replaced

  • Return temperature sensor
  • Wiring harness

Related codes

F.012

Your boiler is having trouble reading the temperature of your hot water, which means it has stopped providing hot water to your taps to prevent the system from overheating.

High Engineer only £120-200

Parts commonly replaced

  • Domestic hot water NTC sensor
  • Wiring harness

Related codes

F.013

Your boiler has lost the connection to the temperature sensor inside your hot water cylinder, which means it cannot accurately tell if your water is hot enough.

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder temperature sensor
  • Wiring harness

Related codes

F.020

Your boiler has detected that it is running too hot because it does not have enough water inside the system to function safely.

High DIY-safe £80-150

What to check first

  1. Check your boiler's pressure gauge on the front display; if it is below 1.0 bar, the system needs more water.
  2. Locate the filling loop (usually a silver braided hose with one or two valves) underneath the boiler.
  3. Open the valves slowly to top up the system pressure until the needle reaches the green zone (between 1.0 and 1.5 bar), then close the valves tightly.

Parts commonly replaced

  • System pressure sensor
  • Central heating pump
  • NTC thermistor

Related codes

Showing 11–20 of 110
F.022

Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.

High DIY-safe

What to check first

  1. Locate the external filling loop, usually two small valves connected by a flexible silver hose underneath the boiler.
  2. Slowly open the valves to let water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Firmly close both valves and check the display to see if the error code has cleared.

Parts commonly replaced

  • Pressure sensor
  • Expansion vessel
  • Pressure relief valve

Related codes

F.023

Your boiler is struggling because there is air trapped inside the system, which is preventing hot water from circulating effectively.

Medium DIY-safe £100-250

What to check first

  1. Check your boiler's pressure gauge and ensure it is between 1 and 1.5 bar
  2. Bleed all the radiators in your home starting from the lowest floor and working upwards
  3. Top up the system pressure again if it drops after bleeding the radiators
  4. Restart the boiler using the reset button or power switch

Parts commonly replaced

  • Central heating pump
  • Automatic air vent

Related codes

F.024

Your boiler has detected trapped air bubbles that are preventing water from flowing properly and heating up, causing the system to shut down for safety.

High DIY-safe £80-150

What to check first

  1. Check your boiler pressure gauge and ensure it is between 1.0 and 1.5 bar
  2. Top up the pressure using the filling loop if it is below 1.0 bar
  3. Bleed your radiators starting from the ground floor and working your way up to release any trapped air
  4. Reset the boiler using the flame-through-a-cross button on the front panel

Parts commonly replaced

  • Central heating pump
  • System pressure sensor
  • Automatic air vent

Related codes

F.025

Your boiler has detected that it is running much hotter than it should, which has triggered a safety shutdown to prevent damage.

High Engineer only £150-300

Parts commonly replaced

  • Flue gas temperature sensor
  • Wiring harness
  • Main heat exchanger

Related codes

F.027

Your boiler has detected a potential internal gas leak and has shut itself down to keep your home safe.

Emergency Engineer only £250-450

Parts commonly replaced

  • Gas valve
  • Main PCB

Related codes

F.028

Your boiler is trying to start up but is failing to light the flame, which means you currently have no heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition lead
  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

F.029

Your boiler has stopped working because it cannot detect a steady flow of gas to keep its flame lit.

High Engineer only £120-250

Parts commonly replaced

  • Gas valve
  • Ignition lead
  • Flame rectification probe

Related codes

F.032

Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not spinning at the correct speed or is failing to communicate with the main control board.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

F.035

Your boiler is struggling to breathe because the pipe that vents exhaust gases outside is obstructed or blocked.

Emergency Engineer only £120-250

Parts commonly replaced

  • Flue terminal
  • Air pressure switch
  • Fan assembly

Related codes

F.040

Your boiler is struggling to breathe properly because exhaust fumes are getting trapped or recycled back into the system instead of venting outside safely.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue seals
  • Flue assembly components
  • Gas valve
  • Air pressure switch

Related codes

Showing 21–30 of 110
F.042

Your boiler has detected a faulty connection to the part that manages the gas supply, meaning it has safely shut itself down to prevent unsafe operation.

High Engineer only £150-250

Parts commonly replaced

  • Gas valve wiring harness
  • Gas valve assembly

Related codes

F.044

Your boiler is struggling to breathe properly because exhaust fumes are being trapped or pulled back into the system, preventing it from burning fuel safely.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue seals
  • Flue assembly
  • Burner gasket
  • Ignition/Ionisation electrode

Related codes

F.047

Your boiler is having trouble reading the temperature of the water being sent to your taps, which means it cannot heat your hot water properly.

High Engineer only £120-220

Parts commonly replaced

  • Domestic hot water temperature sensor
  • Wiring harness

Related codes

F.049

Your boiler's communication system has detected a wiring error, which is preventing it from sending instructions to your heating controls.

High Engineer only £120-250

Parts commonly replaced

  • eBUS wiring harness
  • PCB main control board
  • External heating controller

Related codes

F.057

Your boiler's electronic brain can no longer safely manage the fuel and air mixture required to burn gas, meaning it has shut down completely to prevent an unsafe condition.

High Engineer only £250-450

Parts commonly replaced

  • Gas valve
  • Electronic control board (PCB)
  • Air pressure sensor

Related codes

F.061

Your boiler is having trouble communicating with the part that controls the gas flow, so it has safely shut itself down to prevent any issues.

High Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

F.062

Your boiler has detected an issue with the valve that controls its gas supply, meaning it is not shutting down as quickly as it should for safety reasons.

Emergency Engineer only £200-350

Parts commonly replaced

  • Gas valve
  • Main PCB

Related codes

F.063

The boiler's internal computer is experiencing a memory error, meaning it cannot correctly save or load its operating settings.

High Engineer only £250-400

Parts commonly replaced

  • Main PCB

Related codes

F.064

Your boiler has identified a faulty internal sensor that is preventing it from correctly measuring temperatures, causing it to shut down to stay safe.

High Engineer only £150-250

Parts commonly replaced

  • NTC Temperature sensor
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

F.065

Your boiler has automatically shut down because its internal control board has become too hot.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Internal wiring harness

Related codes

Showing 31–40 of 110
F.067

Your boiler has detected an issue with its internal flame sensor, which means it cannot safely confirm whether the fire inside is burning correctly, so it has shut down as a precaution.

High Engineer only £180-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame rectification electrode
  • Wiring harness

Related codes

F.068

Your boiler's electronic control centre is struggling to properly detect the flame, which is preventing it from staying lit reliably.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Flame sensor electrode
  • Wiring harness

Related codes

F.070

Your boiler's computer has been reset and needs a specific security code to be re-entered by an engineer to confirm it is configured for your home.

High Engineer only £90-160
F.071

Your boiler is struggling to accurately measure the temperature of the water flowing through the system, causing it to shut down for safety.

High Engineer only £120-220

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness

Related codes

F.072

Your boiler has detected an inconsistent temperature reading between its internal sensors, causing it to shut down for safety to prevent overheating.

High Engineer only £150-250

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Return temperature sensor (NTC)
  • Wiring harness

Related codes

F.074

Your boiler's internal sensor that detects water pressure has lost its electrical connection, so the system can no longer confirm it is safe to operate.

High Engineer only £120-220

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.075

Your boiler is struggling to detect the movement of water when it tries to start, likely because a sensor is misreading the internal pressure.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

F.076

Your boiler has detected an issue with the internal electrical connections linked to its safety system, causing it to shut down to prevent potential overheating.

High Engineer only £150-300

Parts commonly replaced

  • Wiring harness
  • Overheat thermostat
  • Main PCB

Related codes

F.077

Your boiler has detected an issue with the safety flap that controls the flow of exhaust gases, so it has safely shut itself down to prevent any unsafe operation.

High Engineer only £150-300

Parts commonly replaced

  • Flue non-return flap
  • Condensate pump
  • PCB

Related codes

F.078

Your boiler has detected that an electronic part inside it is incompatible or not configured correctly, preventing it from starting up safely.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • UI Interface Module

Related codes

Showing 41–50 of 110
F.080

Your boiler is struggling to accurately measure the temperature of the water coming into the system, which may affect your hot water performance.

Low Engineer only £150-250

Parts commonly replaced

  • Cold water NTC sensor
  • Wiring harness

Related codes

F.081

Your boiler has lost the internal connection needed to send hot water to your separate hot water cylinder, meaning you will currently have no hot water.

High Engineer only £150-300

Parts commonly replaced

  • Wiring harness
  • PCB
  • Cylinder NTC sensor

Related codes

F.083

Your boiler is struggling to heat up because there is either not enough water in the system or the water isn't circulating properly.

High DIY-safe £100-250

What to check first

  1. Check your boiler pressure gauge; if it is below 1 bar, use the filling loop to top it up to approximately 1.5 bar
  2. Once pressure is restored, reset the boiler using the flame/reset button
  3. Check all radiators for cold spots that might indicate air locks in the system

Parts commonly replaced

  • System pressure sensor
  • Circulation pump
  • NTC thermistor

Related codes

F.084

Your boiler is confused because its internal temperature sensors are giving conflicting readings, suggesting that the components that measure heat are not detecting it where they expect to.

High Engineer only £150-250

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Wiring harness

Related codes

F.085

Your boiler is confused because its temperature monitoring sensors have been fitted to the wrong pipes, preventing it from knowing if your heating is working correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

F.087

Your boiler is unable to start because a lead responsible for triggering the ignition has become loose or disconnected.

High Engineer only £120-250

Parts commonly replaced

  • Ignition lead
  • Ignition transformer
  • Main PCB

Related codes

F.088

Your boiler has lost its electrical connection to the internal valve that controls gas flow, meaning it cannot safely ignite to provide heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Gas valve wiring harness
  • Gas valve assembly
  • Main printed circuit board (PCB)

Related codes

F.089

Your boiler has detected that the water pump currently installed is not the correct type for your specific model, preventing the heating system from operating properly.

High Engineer only £250-450

Parts commonly replaced

  • High-efficiency circulation pump
  • Printed Circuit Board

Related codes

F.090

Your boiler has lost its connection to the hot water storage component, meaning it cannot properly communicate with or heat your water supply.

High Engineer only £150-250

Parts commonly replaced

  • Wiring harness
  • Communication cable
  • Cylinder sensor

Related codes

F.092

Your boiler's computer system is confused because it has not been correctly set up to use the type of gas currently being supplied to your home.

High Engineer only £120-200
Showing 51–60 of 110
F.095

Your boiler is struggling to breathe properly because exhaust gases are either being trapped inside or getting sucked back into the air intake.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue assembly seals
  • Gas valve
  • PCB

Related codes

F.096

Your boiler is struggling to receive enough gas to run properly, so it has shut down to keep you safe.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Gas meter regulator
  • Gas supply pipework

Related codes

F.097

Your boiler's computer brain has detected an internal error while running its own safety checks and has stopped working to prevent potential damage.

High Engineer only £350-550

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

F.105

Your boiler's computer has lost the specific internal calibration settings required to mix the gas and air correctly, meaning it cannot safely start up.

High Engineer only £120-250

Parts commonly replaced

  • Gas valve
  • Main PCB

Related codes

F.194

Your boiler's main computer is failing to receive the consistent electrical power it needs to function, causing the system to shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
  • Power supply unit

Related codes

F.195

Your boiler has detected that the incoming electricity supply is not strong enough to power it properly, which has caused it to shut down for safety.

High Engineer only £120-250

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

F.196

Your boiler has detected an unstable or dangerously high electrical voltage coming from your home's power supply.

High Engineer only £150-350

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Surge protection device
  • Wiring harness

Related codes

F.317

Your boiler is struggling to detect if you are running the hot tap, which means it may fail to heat your water properly.

Medium Engineer only £150-250

Parts commonly replaced

  • Flow sensor
  • Wiring harness

Related codes

F.318

Your boiler is struggling to switch between heating your radiators and heating your hot water, which means one or both might stop working properly.

High Engineer only £180-300

Parts commonly replaced

  • Diverter valve motor
  • 3-port diverter valve assembly
  • Wiring harness

Related codes

F.320

Your boiler has detected that the internal pump, which moves water around your heating system, is struggling to turn because of debris or sludge in the water.

High Engineer only £180-350

Parts commonly replaced

  • Central heating pump
  • System filter

Related codes

Showing 61–70 of 110
F.321

Your boiler has detected that the water pump responsible for circulating heat is not working correctly, which means the system cannot provide heating or hot water.

High Engineer only £250-450

Parts commonly replaced

  • Central heating pump
  • Pump wiring harness
  • Printed Circuit Board

Related codes

F.322

Your boiler's water pump has become too hot and has automatically shut down to prevent damage, which will stop your heating and hot water from working.

High Engineer only £200-450

Parts commonly replaced

  • Heating pump
  • Pump electronics module
  • Printed circuit board (PCB)

Related codes

F.323

Your boiler has trapped air inside its system, which is preventing the internal water pump from moving heat around your home properly.

High DIY-safe £90-180

What to check first

  1. Check your boiler pressure gauge to ensure it is between 1.0 and 1.5 bar.
  2. If low, use the filling loop to top up the system pressure to the correct level.
  3. Bleed your radiators starting from the ground floor and moving upwards to release any trapped air.

Parts commonly replaced

  • Automatic air vent
  • System pressure sensor
  • Heating pump

Related codes

F.324

Your boiler has lost its electrical connection to the internal water pump, which means it cannot circulate heat and has stopped working.

High Engineer only £150-250

Parts commonly replaced

  • Boiler pump
  • Pump wiring harness
  • Main PCB

Related codes

F.325

Your boiler has detected that the internal pump, which moves water around your heating system, is stuck or struggling to operate properly.

High Engineer only £200-400

Parts commonly replaced

  • High-efficiency pump
  • Pump wiring harness
  • Printed Circuit Board (PCB)

Related codes

F.326

Your boiler is struggling to switch between providing hot water for your taps and heating for your radiators, meaning one or both may stop working properly.

High Engineer only £200-350

Parts commonly replaced

  • Diverter valve motor
  • Diverter valve cartridge
  • PCB

Related codes

F.327

Your boiler is confused because it thinks the pipework for your hot water tank hasn't been set up correctly, which is stopping it from working properly.

High Engineer only £120-250

Parts commonly replaced

  • PCB
  • Wiring harness
  • Flow sensor

Related codes

F.330

Your boiler has detected that the water pump responsible for circulating heat around your home is not communicating correctly, meaning your heating and hot water will not work.

High Engineer only £200-450

Parts commonly replaced

  • Central heating pump
  • Wiring harness
  • Main printed circuit board (PCB)

Related codes

F.334

Your boiler's computer does not recognise the setup of the flue system that vents waste gases outside, so it has safely shut down to prevent operation.

High Engineer only £120-250

Parts commonly replaced

  • PCB
  • Flue gas sensor
  • Wiring harness

Related codes

F.336

Your boiler has detected that the flue system setup does not match the manufacturer's settings, meaning the unit cannot safely operate in its current configuration.

High Engineer only £120-250
Showing 71–80 of 110
F.337

Your boiler has detected that the flue components currently installed do not match the specific requirements of your model, preventing it from operating safely.

High Engineer only £150-300

Parts commonly replaced

  • Flue adaptor
  • Air intake seal
  • Printed circuit board

Related codes

F.338

Your boiler has detected a mismatch between its internal settings and the way it is connected to the flue pipe system that vents gases outside.

High Engineer only £120-250

Parts commonly replaced

  • Main PCB
  • Flue sensor

Related codes

F.342

Your boiler is struggling to breathe properly because the internal fan that manages airflow isn't spinning at the correct speed to keep the system running safely.

High Engineer only £180-350

Parts commonly replaced

  • Fan unit
  • Printed Circuit Board (PCB)
  • Venturi

Related codes

F.343

Your boiler has lost its connection to an internal sensor that monitors the air flowing through the system, causing it to shut down for safety reasons.

High Engineer only £150-250

Parts commonly replaced

  • Air mass sensor
  • Wiring harness

Related codes

F.344

Your boiler has lost the digital settings required to safely manage the flame, meaning it cannot operate until these internal electronic values are restored.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flame sensing electrode

Related codes

F.347

Your boiler has detected water inside the part where the flame burns, which is preventing it from starting up safely.

Emergency Engineer only £150-300

Parts commonly replaced

  • Condensate trap
  • Heat exchanger seal
  • Flue assembly

Related codes

F.363

Your boiler's computer screen or main control board is having trouble remembering its settings and communicating correctly, which prevents the boiler from starting.

High Engineer only £250-450

Parts commonly replaced

  • UI Board
  • Main PCB

Related codes

F.707

Your boiler's control panel has lost its connection to the internal computer, meaning it can no longer send instructions to heat your home.

High Engineer only £150-350

Parts commonly replaced

  • User interface display
  • Main PCB
  • Communication cable

Related codes

F.905

Your boiler has detected an electrical overload in the communication system that links its internal parts, causing it to shut down to prevent further damage.

High Engineer only £150-350

Parts commonly replaced

  • Main PCB
  • eBUS interface module
  • Wiring harness

Related codes

L.016

Your boiler has lost its flame while trying to run at its lowest setting, causing it to shut down for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • PCB

Related codes

Showing 81–90 of 110
L.022

Your boiler has detected that there is not enough water flowing through your heating system, which usually means the pressure is too low or a valve is closed.

High DIY-safe £80-150

What to check first

  1. Check the pressure gauge on the front of the boiler; it should read between 1.0 and 1.5 bar.
  2. If the pressure is below 1.0 bar, locate the filling loop (a silver braided hose or internal tap) underneath the boiler.
  3. Slowly open the filling valve to let water in until the needle reaches 1.5 bar, then ensure the valve is tightly closed.

Parts commonly replaced

  • Circulation pump
  • Pressure sensor
  • Filling loop

Related codes

L.025

Your boiler is having trouble sensing the temperature of the incoming cold water, which may prevent it from providing hot water correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Cold water NTC sensor

Related codes

L.032

Your boiler is struggling to accurately measure the flow of water circulating through the system, which prevents it from operating reliably to heat your home or provide hot water.

High Engineer only £180-300

Parts commonly replaced

  • Flow sensor
  • Wiring harness

Related codes

L.095

Your boiler has detected that a component controlling the gas flow is stuck or operating outside of its expected range, preventing it from firing up safely.

High Engineer only £250-400

Parts commonly replaced

  • Gas valve
  • PCB

Related codes

L.096

Your boiler has detected that the internal gas control system is struggling to adjust correctly, preventing it from starting up safely.

High Engineer only £200-350

Parts commonly replaced

  • Gas valve
  • PCB

Related codes

L.097

Your boiler is struggling to mix the right amount of air with the gas needed for safe and efficient burning.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Venturi
  • Fan assembly

Related codes

L.105

Your boiler is struggling to clear trapped air from its system, preventing it from starting up correctly.

High Engineer only £120-250

Parts commonly replaced

  • Automatic air vent
  • System pump
  • Pressure sensor

Related codes

L.144

Your boiler is struggling to detect the flame needed to heat your water and home, so it has shut itself off for safety.

High Engineer only £150-300

Parts commonly replaced

  • Flame rectification electrode
  • Ignition lead
  • Main PCB

Related codes

L.194

Your boiler's main control system is experiencing an electrical fault, meaning the internal computer cannot receive the power it needs to operate the heating and hot water.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Power supply module

Related codes

L.195

Your boiler is struggling because the electricity supply it is receiving is weaker than it should be.

Medium Engineer only £120-250

Parts commonly replaced

  • Main PCB
  • Wiring harness
  • External power supply/fused spur

Related codes

Showing 91–100 of 110
L.196

Your boiler has detected an unstable or abnormally high electrical supply from your home mains, causing it to shut down to protect its internal electronics.

High Engineer only £150-350

Parts commonly replaced

  • Main PCB
  • Surge protection fuse
  • Wiring harness

Related codes

L.319

Your boiler is struggling to circulate water properly because a built-in safety valve that manages water flow is blocked or stuck.

High Engineer only £150-250

Parts commonly replaced

  • Internal bypass valve
  • Diverter valve
  • Central heating pump

Related codes

L.320

Your boiler has detected that the internal water pump is stuck and is currently trying to clear the blockage itself.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • Pump head

Related codes

L.322

Your boiler has detected that the water circulation pump is running too hot and has stopped working to prevent further damage.

High Engineer only £250-450

Parts commonly replaced

  • Central heating pump
  • Printed Circuit Board

Related codes

L.343

Your boiler has detected an issue with how it measures the flow of air required for safe combustion, so it has safely shut down to prevent any risk.

High Engineer only £150-300

Parts commonly replaced

  • Air pressure sensor
  • Wiring harness
  • Printed Circuit Board (PCB)

Related codes

N.013

Your boiler is struggling to read its internal water pressure correctly, so it has shut down as a precaution to prevent damage.

High Engineer only £150-250

Parts commonly replaced

  • Water pressure sensor
  • Wiring harness

Related codes

N.027

Your boiler is struggling to accurately measure the temperature of the water used for your taps and shower, which will likely prevent it from heating your hot water properly.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness

Related codes

N.032

Your boiler is struggling to detect the water flow correctly, likely due to trapped air or a faulty sensor, which is preventing it from heating your home properly.

Medium Engineer only £150-250

Parts commonly replaced

  • Flow sensor
  • Wiring harness

Related codes

N.089

Your boiler has detected that the internal water pump is not the correct model for this specific unit, preventing it from functioning properly.

High Engineer only £250-450

Parts commonly replaced

  • High-efficiency circulation pump

Related codes

N.095

Your boiler is struggling to breathe properly because exhaust fumes are getting trapped or blocked, making it unsafe to operate.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue assembly seals
  • Gas valve
  • PCB

Related codes

Showing 101–110 of 110
N.096

Your boiler is struggling to receive enough gas to run safely, which has caused it to lock out to prevent damage.

Emergency Engineer only £150-350

Parts commonly replaced

  • Gas valve
  • Gas meter regulator
  • Gas supply pipework

Related codes

N.097

Your boiler is struggling to breathe properly because exhaust fumes are getting trapped or recycled back into the system instead of venting outside safely.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue seal
  • Flue terminal
  • Air intake pipe
  • Fan assembly

Related codes

N.100

Your boiler has lost the connection to the small sensor located outside your home that tells it how cold it is so it can adjust your heating automatically.

Low Engineer only £100-200

Parts commonly replaced

  • Outdoor temperature sensor
  • Wiring loom

Related codes

N.144

Your boiler is struggling to breathe because it is pulling in its own exhaust fumes or the flue is blocked, which prevents it from igniting safely.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue assembly seals
  • Air intake gaskets
  • Ionisation electrode

Related codes

N.194

Your boiler has detected an internal electrical fault preventing the main control system from powering up correctly, which means your heating and hot water will not work.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Power Supply Unit

Related codes

N.270

Your boiler is struggling to heat your water properly because a small filter at the water inlet has become clogged with debris.

Medium Engineer only £120-220

Parts commonly replaced

  • Cold water inlet strainer
  • Secondary heat exchanger

Related codes

N.317

Your boiler is having trouble detecting the flow of water because of a loose or damaged internal wire, which means it cannot reliably provide hot water.

High Engineer only £150-250

Parts commonly replaced

  • Flow sensor harness
  • Volume flow sensor

Related codes

N.319

Your boiler is struggling to circulate water properly because a small internal valve meant to regulate flow has become clogged with debris.

Medium Engineer only £150-250

Parts commonly replaced

  • Bypass valve
  • Diverter valve
  • System filter

Related codes

N.324

Your boiler has lost its connection to the internal water pump, which means it cannot circulate heat around your home and will stop working.

High Engineer only £150-250

Parts commonly replaced

  • Wiring harness
  • High-efficiency pump

Related codes

N.343

Your boiler's internal sensor that measures airflow has a loose connection, preventing the unit from starting safely.

High Engineer only £120-220

Parts commonly replaced

  • Air-mass flow sensor
  • Wiring harness

Related codes

171 operating states & engineer diagnostics

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

D.000 Diagnostic Your boiler is currently set to run at a lower power level than its maximum capacity to save energy or match your home's heat demand. D.001 Diagnostic Your boiler is simply running its internal water pump for a bit longer than usual to ensure all the leftover heat is safely moved away from the burner after the heating has switched off. D.002 Diagnostic Your boiler is perfectly fine and is simply taking a short, programmed break to prevent overheating before it starts the heating cycle again. D.003 Diagnostic Your boiler is simply reporting the current temperature of the water being heated for your taps and shower. D.004 Diagnostic Your boiler is struggling to accurately read the temperature of the water being heated for your taps and shower. D.005 Diagnostic This code is not a fault; it is simply showing the current temperature setting the boiler is trying to reach for your radiators. D.006 Diagnostic The boiler is simply displaying the current temperature setting for your hot water, which is a status message rather than a breakdown. D.008 Diagnostic Your boiler is currently receiving a signal from your wall thermostat indicating that it is calling for heat, but it is not a system fault. D.009 Diagnostic Your boiler is struggling to communicate with its internal control system or external thermostat, which is preventing it from knowing whether to turn on your heating or hot water. D.010 Diagnostic Your boiler is signalling that the internal pump, which moves water around your heating system, is not operating as it should. D.011 Diagnostic Your boiler is signalling that it is currently controlling or communicating with an external pump that helps circulate water through your heating system. D.012 Diagnostic Your boiler is currently running a routine check on the pump that moves hot water to your separate hot water storage tank. D.013 Diagnostic Your boiler is struggling to move water around the system, which means it cannot heat your home or provide hot water effectively. D.015 Diagnostic Your boiler is reporting a technical reading regarding how fast the internal water pump is spinning, which is usually a sensor or communication issue rather than a mechanical failure. D.016 Diagnostic Your boiler is struggling to communicate with your thermostat or controller, which may cause your heating to stay off or behave inconsistently. D.017 Diagnostic Your boiler has detected that the external heating controller or room thermostat is not communicating correctly with the system. D.018 Diagnostic Your boiler is simply indicating that the internal water pump is currently running to move heat around your system. D.020 Diagnostic Your boiler is currently displaying a status message indicating it is in the process of calibrating the maximum water temperature for your taps and shower. D.021 Diagnostic Your boiler is currently monitoring the status of its warm start feature, which ensures hot water is ready quickly when you turn on a tap. D.022 Diagnostic Your boiler is currently operating exactly as it should and is letting you know that it is actively heating your hot water. D.023 Diagnostic Your boiler is currently waiting for a signal to start heating, which is a normal part of its operation. D.025 Diagnostic Your boiler is simply indicating that it is currently receiving a request to provide hot water to your taps or shower. D.026 Diagnostic Your boiler has detected an issue with an internal electrical switch that helps coordinate its components, which may prevent it from operating correctly. D.027 Diagnostic Your boiler has detected an issue with an external device connected to it, such as a remote control, timer, or external pump, causing the communication link to fail. D.028 Diagnostic Your boiler has detected an issue with an external accessory, such as a heating pump or an add-on control device, preventing it from communicating with the system correctly. D.029 Diagnostic Your boiler is struggling to circulate water properly through your heating system, which is usually caused by a blockage, trapped air, or a faulty pump. D.031 Diagnostic Your boiler is struggling to automatically top up its internal water pressure, which may prevent your heating or hot water from turning on. D.033 Diagnostic Your boiler is struggling to reach or maintain the correct fan speed, which prevents it from safely venting gases and firing up properly. D.034 Diagnostic Your boiler is struggling to detect the speed of its internal fan, which is essential for safely venting exhaust gases and keeping the burner running. D.035 Diagnostic Your boiler is struggling to switch between heating your radiators and heating your hot water because the internal diverter valve is stuck or not responding. D.036 Diagnostic Your boiler is struggling to detect a consistent flow of water when you turn on your hot tap, likely due to a sensor issue or a blockage. D.039 Diagnostic Your boiler is struggling to accurately measure the temperature of the incoming cold water, which may cause your hot water taps to run at an inconsistent temperature. D.040 Diagnostic Your boiler is struggling to accurately read how hot the water is as it leaves the unit, which is preventing it from heating your home properly. D.041 Diagnostic Your boiler is struggling to accurately measure the temperature of the water returning to it from your radiators. D.043 Diagnostic Your boiler is displaying a status code related to its internal heating settings rather than a breakdown, meaning it is simply calculating the required water temperature based on your current configuration. D.045 Diagnostic Your boiler's internal computer is reporting an unusual calculation error regarding the temperature settings, which may result in your heating being slightly warmer or cooler than you requested. D.047 Diagnostic Your boiler is struggling to read the temperature from the sensor installed outside your home, so it is using a default setting to keep your heating running. D.052 Diagnostic Your boiler is having difficulty communicating with the valve that controls the flow of gas, which means it cannot safely ignite or heat your water. D.058 Diagnostic Your boiler is currently waiting for a signal from your solar water heating system to decide if it needs to help boost the temperature of your hot water. D.060 Diagnostic Your boiler has detected that it has been running too hot multiple times and is recording these instances to help a heating engineer diagnose a persistent circulation or heat exchange issue. D.061 Diagnostic Your boiler has failed to start up several times in a row, so it has locked itself for safety to prevent gas buildup. D.062 Diagnostic Your boiler is currently running in an energy-saving night mode, which is a normal setting rather than a technical fault. D.064 Diagnostic Your boiler is struggling to light the flame consistently and is recording that it takes longer than normal to ignite. D.065 Diagnostic Your boiler has failed to light the gas flame after several attempts and has now safely shut down to prevent gas from building up. D.066 Diagnostic Your boiler is signalling that the 'warm start' feature, which keeps a small amount of water pre-heated for faster hot water taps, is currently active or adjusting. D.067 Diagnostic Your boiler is currently in a brief, automatic resting period to prevent it from wearing out by switching on and off too frequently. D.068 Diagnostic Your boiler is struggling to light the flame on the first try, which may be caused by a temporary interruption in gas supply or a buildup of debris around the ignition sensor. D.069 Diagnostic Your boiler is failing to light because it has tried to start twice and failed to detect a flame. D.070 Diagnostic Your boiler is struggling to direct heat between your radiators and your hot water taps because a small motorized part inside is not responding correctly. D.071 Diagnostic Your boiler is temporarily limiting the heat of the water flowing through it because it has reached its maximum set temperature limit. D.072 Diagnostic Your boiler is currently running its internal pump to move excess heat away from the water tank after it has finished heating up. D.073 Diagnostic Your boiler is struggling to accurately detect or manage the temperature for its quick-start hot water function. D.074 Diagnostic Your boiler is currently running a routine automated cycle to heat your water cylinder to a high temperature to ensure it remains hygienic and free from bacteria. D.075 Diagnostic Your boiler is struggling to heat your hot water cylinder within a set time limit, often because the water isn't getting hot enough or the system is taking too long to reach the desired temperature. D.077 Diagnostic Your boiler is currently running at its highest possible power setting to heat your water, which is a normal operational state rather than a mechanical fault. D.078 Diagnostic Your boiler is limiting the temperature of the hot water it produces, usually because the heating system is currently prioritising the water temperature for your taps and shower. D.080 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your home and is not an error at all. D.081 Diagnostic This code is simply an information display showing the total number of hours your boiler has spent heating your hot water, and is not a fault or a sign of a problem. D.082 Diagnostic Your boiler is simply showing that it is currently in the process of starting up the burner to provide heat to your radiators. D.083 Diagnostic Your boiler is simply indicating that it is currently preparing or starting the burner to heat your domestic hot water. D.084 Diagnostic Your boiler is simply reminding you that it has reached the internal clock limit set for its regular annual maintenance check. D.085 Diagnostic Your boiler is signalling that it cannot reach the minimum amount of heat output it needs to run properly, which usually indicates an issue with the gas supply or the internal control system. D.088 Diagnostic Your boiler is struggling to detect enough water flowing through the system to safely trigger your hot water supply. D.090 Diagnostic Your boiler is having trouble communicating with its external thermostat or control unit. D.091 Diagnostic Your boiler is struggling to pick up the radio signal that automatically sets its internal clock. D.092 Diagnostic Your boiler is having difficulty communicating with the sensor that detects the temperature of your hot water storage system. D.093 Diagnostic Your boiler has lost its identity settings, which means the internal computer does not know exactly which model of boiler it is controlling. D.094 Diagnostic Your boiler has performed a routine reset of its error log and there is no active fault preventing it from working. D.095 Diagnostic Your boiler is displaying an internal software version number on the screen, which is typically a status notification rather than a breakdown. D.096 Diagnostic Your boiler has lost its configured settings, possibly due to a power surge or a memory error, and needs to be re-calibrated by a professional. D.098 Diagnostic Your boiler has lost communication with a small plug-in component that tells it exactly which model it is, meaning it cannot operate until this identity connection is restored. D.124 Diagnostic Your boiler is simply displaying a status message indicating that a smart energy-saving feature is currently active and functioning as intended. D.125 Diagnostic Your boiler is struggling to accurately read or maintain the temperature of the water being sent to your taps and showers. D.128 Diagnostic Your boiler has detected that the water temperature is struggling to reach the level required to heat your home effectively. D.129 Diagnostic Your boiler is struggling to register that you are requesting hot water because the flow sensor is having trouble detecting the water movement. D.145 Diagnostic Your boiler has detected that the flue pipe is blocked or restricted, meaning it cannot safely vent exhaust gases outside. D.146 Diagnostic Your boiler has reached its internal limit for how many times the flame-sensing part can be used, and it needs a professional to replace this component to ensure the system remains safe and reliable. D.147 Diagnostic Your boiler is failing to detect the flame properly, which means it will stop working to prevent an unsafe build-up of unburnt gas. D.156 Diagnostic Your boiler is currently stuck in a configuration mode that is waiting for a formal settings update to confirm the type of gas supply it is using. D.157 Diagnostic Your boiler has lost the information about which type of gas it should be using, which prevents it from safely igniting. D.158 Diagnostic Your boiler is having trouble balancing the mixture of gas and air needed to burn fuel efficiently, which prevents it from firing up correctly. D.159 Diagnostic Your boiler is temporarily pausing between heating cycles to protect itself from excessive wear and tear; this is a standard status message rather than a breakdown. D.160 Diagnostic Your boiler is displaying a status message indicating it is currently checking or calibrating the internal water pressure levels. D.161 Diagnostic Your boiler has reached its scheduled annual service date, so it is simply reminding you that it is time for a professional maintenance check-up. D.162 Diagnostic Your boiler is struggling to communicate with its outdoor temperature sensor, meaning it cannot automatically adjust your heating based on the weather outside. D.163 Diagnostic Your boiler has detected an internal communication error with an external add-on component, such as a heating controller or external pump connection. D.164 Diagnostic Your boiler is notifying the system that it has been set up with a specific type of exhaust pipe, which is a configuration setting rather than a broken part. D.166 Diagnostic Your boiler's internal computer is struggling to read data from its sensors, which prevents it from safely controlling your heating and hot water. D.167 Diagnostic Your boiler is struggling to communicate with your hot water storage tank, meaning it cannot properly manage your water heating. D.170 Diagnostic Your boiler is currently performing a routine internal check or calibration of its internal water flow system. D.171 Diagnostic Your boiler is struggling to accurately read or maintain the correct internal water pressure needed to run safely and effectively. D.172 Diagnostic Your boiler is struggling to manage the temperature difference between the water it heats up and the water returning from your radiators. D.173 Diagnostic Your boiler has detected that the water pressure inside your heating system has dropped too low to operate safely. D.174 Diagnostic Your boiler has detected that the water pressure inside the heating system has risen above the safe operating limit. D.175 Diagnostic Your boiler is struggling to circulate water effectively, which means it may not be able to provide consistent heating or hot water. D.182 Diagnostic Your boiler is having difficulty communicating with the gas valve, which is preventing it from lighting the flame correctly. D.185 Diagnostic Your boiler is struggling to process its internal setup instructions, meaning it has paused operation to prevent incorrect settings from causing damage. D.186 Diagnostic Your boiler has detected that the flue system configuration settings are not correctly programmed for your specific installation. D.187 Diagnostic Your boiler is currently in a configuration mode waiting for a technician to confirm the type of flue system installed, which prevents it from operating. I.003 Diagnostic Your boiler is simply reminding you that it is due for its annual service to ensure it remains safe and efficient. I.020 Diagnostic Your boiler has detected that the water pressure in your heating system has dropped too low, so it has temporarily stopped working to protect itself. I.144 Diagnostic Your boiler's internal sensor that checks for safe burning is showing signs of age and needs to be replaced to ensure the unit continues to operate safely and efficiently. P.000 Diagnostic Your boiler is currently running a routine process to clear air bubbles out of the system pipes after a restart or maintenance. P.2 Diagnostic Your boiler is currently running a background self-test to check it can operate safely at its lowest power setting. P.008 Diagnostic Your boiler is currently in the middle of a process where it is filling itself with water to reach the correct pressure level. S.0 Status Your boiler is working perfectly fine and is simply in standby mode because your thermostat is not currently asking for the heating to be turned on. S.000 Status Your boiler is currently in standby mode because it has not been asked to provide any heating or hot water. S.1 Status Your boiler is preparing to ignite but is stuck at the stage where the internal fan is spinning up to clear the combustion chamber. S.001 Status Your boiler is simply preparing itself to start heating your home and is currently getting the internal air circulation system ready. S.2 Status Your boiler is currently moving water through the system after a heating or hot water cycle to cool down the internal components safely. S.002 Status Your boiler is perfectly fine; it is simply preparing itself to start heating your radiators by circulating water. S.003 Status Your boiler is operating normally and is currently firing up to provide central heating to your home. S.4 Status Your boiler is operating normally and is currently in the process of starting up the burner to provide heat or hot water. S.004 Status Your boiler is working exactly as it should be to heat your radiators or provide hot water. S.005 Status Your boiler is simply finishing its normal cooling cycle after heating your home and is operating exactly as it should. S.006 Status Your boiler is currently running normally and is finishing a cycle by clearing leftover heat from the system. S.7 Status Your boiler is briefly keeping the internal pump running to safely circulate and dissipate leftover heat after you have finished using your heating or hot water. S.007 Status Your boiler is operating normally and is currently circulating water through the pipes to ensure heat reaches your radiators effectively. S.008 Status Your boiler is working normally and is simply taking a short, programmed rest to prevent it from turning on and off too frequently. S.009 Status Your boiler is performing a routine, automatic self-check to ensure it is burning fuel efficiently as it ages. S.10 Status Your boiler is simply letting you know that it is currently busy heating up water for your taps or shower. S.010 Status Your boiler is currently idle because it has not been asked to provide hot water or heating. S.11 Status Your boiler is simply preparing its internal airflow to heat your water, which is a normal part of its startup process and not an error at all. S.011 Status Your boiler is simply letting you know that it has detected you are running a hot tap and is currently preparing to heat the water for you. S.012 Status Your boiler is simply preparing to heat your tap water, which is a normal part of its routine operation. S.013 Status Your boiler is working exactly as it should and is currently heating up water for your taps or shower. S.014 Status Your boiler is working exactly as it should and is currently heating up water for your taps or shower. S.15 Status Your boiler is simply performing a routine cooling-down process after you last used hot water, and there is no fault with your system. S.015 Status Your boiler is currently busy providing hot water, so it has temporarily paused your radiators to focus on heating your tap water. S.016 Status Your boiler is currently running normally while providing hot water or finishing its cooling cycle, so no action is required. S.17 Status Your boiler is simply finishing its cooling cycle after you have finished using hot water, and no action is required. S.017 Status Your boiler is currently running normally and is finishing up a cycle after you last used the hot water tap. S.019 Status Your boiler is simply performing a routine, automatic internal health check while you are using hot water, and no action is required. S.20 Status Your boiler is not broken; it is simply letting you know that it has received a request to provide hot water and is currently preparing to deliver it. S.020 Status Your boiler is currently in standby mode because it is not receiving a signal that it needs to heat your hot water at this moment. S.021 Status Your boiler is currently heating up a tank of hot water and is operating exactly as it should. S.022 Status Your boiler is currently heating your hot water tank and is preparing the internal pump to circulate the heat, which is a normal part of its operation. S.023 Status Your boiler is currently heating up the water for your taps or shower, and this is simply a status message confirming it is working as expected. S.024 Status Your boiler is currently heating the water stored in your hot water cylinder, which is a normal part of its standard operation. S.025 Status Your boiler is currently busy heating your hot water storage tank and is running its internal systems to ensure the heat is properly distributed. S.026 Status Your boiler is currently busy heating up your hot water storage cylinder and finishing a safety cooling cycle for the fan, which is completely normal operation. S.027 Status Your boiler is currently busy heating your hot water storage tank and finishing its internal cooling cycle, which is a normal operational state. S.028 Status Your boiler is currently waiting for a short period before it can heat your hot water again, which is a normal part of its operation. S.029 Status Your boiler is currently performing a standard, automated self-check to ensure its internal sensors remain accurate as they age. S.030 Status Your boiler is currently in standby mode because it is not receiving a signal from your thermostat to turn on the heating. S.031 Status Your boiler is currently in standby mode because it has not been asked to provide heating or hot water, so it is simply waiting for a signal from your thermostat or taps. S.032 Status Your boiler is struggling to maintain the correct airflow required to burn gas safely, so it is automatically pausing to restart the system. S.034 Status Your boiler is temporarily running its pump to prevent your pipes from freezing because the temperature inside the unit has dropped very low. S.039 Status Your boiler has temporarily stopped working because an external safety switch, such as a flood sensor or a condensate water pump, is signaling that it needs attention. S.041 Status Your boiler has detected that the water pressure inside your heating system is currently set too high for it to operate safely. S.042 Status Your boiler is temporarily waiting for an external accessory, such as a water pump or a vent flap, to finish its task before it can safely fire up. S.054 Status Your boiler is temporarily waiting because the water pressure inside the system is too low for it to operate safely. S.057 Status Your boiler is currently taking a short break to reset its internal combustion safety systems and should restart automatically once the internal check is complete. S.059 Status Your boiler is preventing the heating from starting because it cannot detect enough water flowing through the system. S.088 Status Your boiler is currently performing an automatic air-removal process to clear trapped air from the system, which is a normal maintenance function. S.091 Status Your boiler is currently stuck in a demonstration or testing mode which prevents it from heating your home or water normally. S.092 Status Your boiler is currently running an internal system check to measure the water flow through your heating pipes, which is a normal part of its operation. S.093 Status Your boiler is currently running a background check on its combustion levels but cannot complete the test, usually because it is currently busy heating your water or radiators. S.096 Status Your boiler is currently performing a mandatory internal system check on its temperature sensors and has temporarily paused heating to ensure everything is functioning correctly. S.097 Status Your boiler is currently running a mandatory internal safety check on its water pressure monitoring system and has temporarily paused heating to ensure everything is functioning correctly. S.098 Status Your boiler is currently running an internal system check and has temporarily paused heating and hot water to ensure all sensors are reading correctly. S.109 Status Your boiler has temporarily stopped working because it has entered a standby mode, usually while it waits for a signal from your thermostat or because it needs to take a short break before restarting. S.175 Status Your boiler is currently running through its initial start-up configuration process, which prevents it from heating your water or home until the setup is complete. S.199 Status Your boiler is currently performing an automatic top-up of its internal water pressure system to ensure it stays at the correct level. S.326 Status Your boiler is currently running an internal self-test on its water flow and valve systems to ensure everything is operating correctly. S.328 Status Your boiler has detected that an external water pump is running non-stop even though the boiler has not been told to operate it. S.335 Status Your boiler is currently performing a routine safety check to ensure that air and exhaust fumes can flow freely through your flue pipe. S.341 Status Your boiler has been running for a very long time and has automatically slowed down to save energy and prevent overheating. S.599 Status Your boiler is currently experiencing a general internal system error that is preventing it from operating correctly. T.001 Diagnostic Your boiler is struggling to circulate water properly because the internal mechanism responsible for moving heat around your system is not responding correctly. T.007 Diagnostic Your boiler is currently operating at its lowest possible power setting, which is a normal status message indicating it is gently maintaining your heating temperature.