Ideal Logic Max Heat 2 Fault codes & diagnostics

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

Regular Natural GasLPG 12-30 kW 2022-present
GC Numbers 41-860-2541-860-2641-860-2741-860-2841-860-29
Download the Ideal Logic Max Heat 2 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.
60 High 9 Medium 5 Low
Versions & GC numbers

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
41-860-25 LOGIC MAX HEAT2 H12 2022–present
41-860-26 LOGIC MAX HEAT2 H15 2022–present
41-860-27 LOGIC MAX HEAT2 H18 2022–present
41-860-28 LOGIC MAX HEAT2 H24 2022–present
41-860-29 LOGIC MAX HEAT2 H30 2022–present
Just want the most common Ideal Logic Max Heat 2 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 74 documented codes

Tap any card for details

4.2

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

High DIY-safe £100-£350

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate.
  2. Ensure there is enough pressure in the system by checking the pressure gauge (aim for 1.5 bar).
  3. Press the 'Reset' button on the front of the boiler panel once the unit has cooled down.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Thermistor
Full explanation for 4.2
4.3

Your boiler is failing to light the gas to create heat, so the system has shut itself down for safety.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances, like a cooker, are working to confirm gas supply.
  2. If it is freezing outside, check if the white plastic condensate pipe leading outdoors is frozen.
  3. Press the 'Reset' button on the boiler control panel once.

Parts commonly replaced

  • Ignition electrode
  • Spark generator
  • Gas valve
  • Flame sensing cable

Related codes

Full explanation for 4.3
4.4

Your boiler has detected that there is not enough water pressure or water is not moving through the system properly to operate safely.

High DIY-safe £100-280

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is low, use the filling loop handles underneath the boiler to top it up until the needle reaches the green zone.
  3. Ensure all radiator valves and isolation valves under the boiler are fully open.
  4. Reset the boiler by turning the control knob to 'RE' or pressing the reset button.

Parts commonly replaced

  • Circulating Pump
  • Water Pressure Sensor
  • Automatic Air Vent
Full explanation for 4.4
4.5

Your boiler is failing to keep its flame lit, which means it cannot heat your home or water.

High DIY-safe £120-300

What to check first

  1. Check if other gas appliances in your home, like a hob, are working correctly
  2. Ensure your gas meter has credit if you use a pre-payment meter
  3. Restart the boiler by pressing the 'Reset' button

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Ignition lead
Full explanation for 4.5
4.6

Your boiler's fan, which safely pushes exhaust gases out of the flue, has stopped working correctly and is preventing the boiler from firing up.

High Engineer only £250-450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 4.6
4.7

Your boiler detects a flame when it should be off, which is a safety error that prevents the system from starting up.

High Engineer only £180-450

Parts commonly replaced

  • Gas Valve
  • Ionisation Lead
  • Main PCB
Full explanation for 4.7
4.8

Your boiler has lost its ability to measure the temperature of the water leaving the unit, meaning it cannot safely regulate the heat.

High Engineer only £120-190

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness
  • Main PCB
Full explanation for 4.8
4.9

Your boiler has detected an issue with a temperature sensor that monitors the water returning from your radiators, often resulting in the system shutting down for safety.

High Engineer only £100-180

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for 4.9
4.10

Your boiler has lost communication with the sensor that measures the temperature outdoors, which may cause your heating to run less efficiently.

Low Engineer only £90-180

Parts commonly replaced

  • Outside Weather Compensation Sensor
  • Sensor Wiring

Related codes

Full explanation for 4.10
4.11

Your boiler is not providing central heating even though it may still be providing hot water.

High DIY-safe £100-250

What to check first

  1. Check that your room thermostat or programmer is set higher than the current room temperature
  2. Ensure the heating mode is active on the boiler display
  3. Check that the radiator valves are open and not turned to zero

Parts commonly replaced

  • External Thermostat
  • Motorised Diverter Valve Head
  • Printed Circuit Board (PCB)
Full explanation for 4.11
Showing 11–20 of 74
4.12

Your boiler is providing central heating as normal, but it is currently unable to heat your hot water.

Medium Engineer only £140-£280

Parts commonly replaced

  • Plate Heat Exchanger
  • Diverter Valve Motor
  • DHW Temperature Sensor
  • Flow Turbine
Full explanation for 4.12
4.13

Your boiler has lost power or the screen has failed, meaning it will not operate and you cannot see any settings or status messages.

High DIY-safe £100-350

What to check first

  1. Check if other appliances in the house are working to rule out a general power cut
  2. Check your home's main fuse box (consumer unit) to see if a circuit has tripped
  3. Ensure the boiler's power switch (usually a fused spur near the unit) is turned on

Parts commonly replaced

  • Display PCB
  • Main Control PCB
  • Internal Fuse
Full explanation for 4.13
4.14

Your boiler is providing hot water to your cylinder correctly, but the central heating for your radiators is not working.

Medium DIY-safe £120-250

What to check first

  1. Check that your room thermostat or heating programmer is turned up and calling for heat
  2. Ensure any zone valves (usually found in the airing cupboard) are moving correctly
  3. Reset the boiler by turning the control knob to 'Reset' and then back to the original position

Parts commonly replaced

  • External Zone Valve
  • Room Thermostat
  • Wiring Centre

Related codes

Full explanation for 4.14
4.15

Your boiler is providing central heating for your radiators as normal, but is failing to heat your hot water tank or taps.

Medium Engineer only £180-350

Parts commonly replaced

  • Diverter Valve Actuator
  • DHW Flow Sensor
  • External Cylinder Thermostat

Related codes

Full explanation for 4.15
4.16

Your boiler has lost power or is suffering from a complete electronic failure, meaning the control screen is unresponsive and the heating will not operate.

High DIY-safe £120-400

What to check first

  1. Check if your home's main fuse box has tripped a circuit breaker.
  2. Ensure the boiler's isolation switch (usually a white fused spur near the unit) is turned on.
  3. Check if other appliances in the house are working to rule out a general power cut.

Parts commonly replaced

  • Internal Fuse
  • Printed Circuit Board (PCB)
  • Display User Interface
  • Wiring Harness
Full explanation for 4.16
9.1.5

Your boiler is currently unable to read the water temperature correctly due to a faulty sensor, meaning it has shut down to prevent potential overheating.

High Engineer only £150-250

Parts commonly replaced

  • Header Thermistor (T1)
  • Wiring Harness

Related codes

Full explanation for 9.1.5
9.1.8

Your heat pump is struggling because a sensor that measures the temperature of the refrigerant in the outdoor unit has stopped sending a clear signal, preventing the system from heating your home correctly.

High Engineer only £180-350

Parts commonly replaced

  • T3 Temperature Sensor
  • Wiring harness

Related codes

Full explanation for 9.1.8
13

Your boiler has detected an internal electronic error that is preventing it from starting up safely.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for 13
14

Your boiler has detected an internal logic error within its main control computer and has safely shut itself down to prevent further damage.

High Engineer only £200-400

Parts commonly replaced

  • Main printed circuit board (PCB)

Related codes

Full explanation for 14
16

Your boiler has detected an internal electrical or software error that matches its control system's ability to operate safely.

High Engineer only £150-300

Parts commonly replaced

  • Main printed circuit board (PCB)

Related codes

Full explanation for 16
Showing 21–30 of 74
17

Your boiler has detected an internal software or processing error which prevents it from operating safely.

High Engineer only £200-400

Parts commonly replaced

  • Main printed circuit board (PCB)

Related codes

Full explanation for 17
19

Your boiler has detected that the water returning to it from your radiators is much hotter than expected, causing it to shut down to prevent overheating.

High Engineer only £120-250

Parts commonly replaced

  • Return NTC thermistor
  • System pump
  • Primary heat exchanger

Related codes

Full explanation for 19
25

Your boiler has sensed that the water inside is heating up much faster than it should be, so it has shut down as a precaution to prevent internal damage.

High Engineer only £150-300

Parts commonly replaced

  • Pump
  • System filter
  • Heat exchanger thermistor

Related codes

Full explanation for 25
28

Your boiler has stopped working because it cannot confirm that the internal fan, which is essential for safely exhausting fumes, is spinning correctly.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

Full explanation for 28
29

Your boiler has detected that its internal fan is not spinning or communicating correctly, so it has safely shut down to prevent unsafe operation.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

Full explanation for 29
31

Your boiler has stopped working because a sensor that measures the water temperature has developed an electrical fault and is sending a scrambled signal to the system.

High Engineer only £120-200

Parts commonly replaced

  • Flow Thermistor sensor
  • Wiring harness

Related codes

Full explanation for 31
32

Your boiler has lost its ability to accurately measure the temperature of the water coming back into the system, so it has shut down as a precaution to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return thermistor sensor
  • Wiring harness

Related codes

Full explanation for 32
36

Your boiler has lost the signal from the sensor that monitors the water temperature, meaning it cannot safely regulate its heat and has shut down to protect itself.

High Engineer only £120-220

Parts commonly replaced

  • Flow thermistor
  • Wiring harness
Full explanation for 36
37

Your boiler has lost the connection to a temperature sensor meant to monitor the water returning to it, so it has shut down as a precaution to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return Thermistor
  • Wiring Harness

Related codes

Full explanation for 37
38

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

Medium Engineer only £120-220

Parts commonly replaced

  • Cylinder sensor probe
  • Wiring loom

Related codes

Full explanation for 38
Showing 31–40 of 74
43

Your boiler's computer has detected that its internal settings have become corrupted or are no longer readable, preventing it from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

Full explanation for 43
60

Your boiler's computer is having trouble reading its own internal settings, which is preventing it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for 60
65

Your boiler is struggling to start because the internal fan is not spinning at the correct speed needed for a safe ignition.

High Engineer only £180-300

Parts commonly replaced

  • Fan assembly
  • Fan harness
  • PCB

Related codes

Full explanation for 65
70

Your boiler is failing to light the internal flame, which means it cannot produce any heat or hot water for your home.

High Engineer only £120-250

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Rectification Probe

Related codes

Full explanation for 70
71

Your boiler's computer system has encountered an internal error and cannot process instructions properly, causing it to stop functioning for your safety.

High Engineer only £250-400

Parts commonly replaced

  • Main Control Board
  • Wiring Harness
Full explanation for 71
75

Your boiler has detected an electrical signal issue related to the internal flame sensor, preventing it from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Flame rectification probe
  • Wiring harness
  • Main printed circuit board (PCB)

Related codes

Full explanation for 75
82

Your boiler is providing you with hot water as normal, but it is currently unable to send heat to your radiators.

Medium Engineer only £120-250

Parts commonly replaced

  • Diverter valve motor
  • Diverter valve
  • Central heating sensor
Full explanation for 82
83

Your boiler is currently only providing heating and is failing to trigger the supply of hot water to your taps and shower.

High Engineer only £150-250

Parts commonly replaced

  • Diverter valve
  • Diverter valve motor
  • Domestic hot water flow sensor

Related codes

Full explanation for 83
113

Your boiler has detected an unstable electricity supply, meaning the power coming into the unit is not steady enough for it to operate safely.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for 113
115

Your boiler has detected an internal software or communication error and has safely shut itself down to prevent potential damage.

High Engineer only £150-300

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 115
Showing 41–50 of 74
116

Your boiler’s internal computer is struggling to monitor the electricity supply, which is forcing the system to shut down to prevent damage.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB

Related codes

Full explanation for 116
Blocked Flue/Condensate

Your boiler has stopped working because it cannot safely get rid of waste gases or excess water through its external pipes.

High DIY-safe £90-180

What to check first

  1. Check the external plastic condensate pipe for signs of ice or blockages and thaw with warm water if frozen.
  2. Inspect the flue outlet on your outside wall to ensure it isn't obstructed by debris, leaves, or bird nests.
  3. Restart the boiler using the reset button once any external obstructions are cleared.

Parts commonly replaced

  • Condensate trap
  • Flue fan
  • Air pressure switch

Related codes

Full explanation for Blocked Flue/Condensate
E4

Your boiler has lost the ability to tell how hot your water cylinder is, meaning it may stop heating your hot water tank until the sensor is fixed.

Medium Engineer only £120-200

Parts commonly replaced

  • DHW Cylinder Sensor
  • Wiring Harness

Related codes

Full explanation for E4
EA

Your boiler has detected a problem with a temperature sensor, which is preventing it from safely heating your water or home.

High Engineer only £120-200

Parts commonly replaced

  • DHW thermistor
  • Wiring harness

Related codes

Full explanation for EA
Ed

Your boiler is having trouble reading the outdoor temperature, which prevents it from adjusting your heating correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Outdoor temperature sensor
  • Wiring harness
Full explanation for Ed
F9

The computer brain inside your boiler has lost its settings or suffered a hardware failure, meaning it cannot operate safely or effectively.

High Engineer only £250-400

Parts commonly replaced

  • Main Control PCB
  • Wiring harness

Related codes

Full explanation for F9
Fan Fault

Your boiler has stopped working because the internal fan, which safely clears exhaust fumes, is not running correctly.

High Engineer only £220-£380

Parts commonly replaced

  • Fan motor assembly
  • PCB (Main control board)
  • Fan wiring harness
Full explanation for Fan Fault
Fd

Your boiler has stopped working because it cannot detect water moving through the system to keep it running safely.

High DIY-safe £100-£350

What to check first

  1. Check that your external heating valves or isolation valves are fully open.
  2. Ensure your radiator valves (TRVs) are turned up and not all closed.
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it is too low.
  4. Gently bleed your radiators to remove any trapped air pockets.

Parts commonly replaced

  • Circulation Pump
  • Pump Head
  • Flow Pipe Thermistor
Full explanation for Fd
Flame Loss

Your boiler is trying to stay lit but the flame keeps going out, so it has safely shut itself down to prevent any issues.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Flame rectification probe
  • Gas valve

Related codes

Full explanation for Flame Loss
Flame On Before Gas On

Your boiler incorrectly thinks it sees a flame before it has even started the ignition process, which is a safety error that prevents it from starting up.

High Engineer only £120-350

Parts commonly replaced

  • Flame sense electrode
  • Printed Circuit Board (PCB)
  • Gas valve
Full explanation for Flame On Before Gas On
Showing 51–60 of 74
Flame on before gas valve on

Your boiler has detected a flame when there shouldn't be one, which means the internal sensors or ignition parts are sending incorrect signals to the control board.

High Engineer only £120-300

Parts commonly replaced

  • Ignition Electrode
  • Spark Generator
  • Main Printed Circuit Board (PCB)
Full explanation for Flame on before gas valve on
Flow Thermistor Fault

Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, causing it to shut down as a safety precaution.

High Engineer only £90-180

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness
Full explanation for Flow Thermistor Fault
Flow/Return Reversed

Your boiler has detected that your heating pipes have been connected the wrong way around, preventing it from heating your home properly.

High Engineer only £150-300

Parts commonly replaced

  • Pipework reconfiguration
  • Flow sensor

Related codes

Full explanation for Flow/Return Reversed
FUSE

Your boiler has stopped working because an internal safety fuse has blown, cutting off the power needed for its control system to function.

High Engineer only £120-220

Parts commonly replaced

  • Main control board
  • 24V internal fuse
  • Wiring harness

Related codes

Full explanation for FUSE
Gas Valve Fault

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

High Engineer only £250-£450

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for Gas Valve Fault
H0

Your boiler has lost the communication link with its outdoor sensor, meaning it cannot accurately gauge the temperature outside to adjust your heating automatically.

Low Engineer only £120-200

Parts commonly replaced

  • Outdoor temperature sensor
  • Wiring harness
  • PCB

Related codes

Full explanation for H0
Ignition Lockout

Your boiler is failing to light the flame needed to provide heating and hot water, so it has safely shut itself down.

High Engineer only £120-250

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Generator

Related codes

Full explanation for Ignition Lockout
L A

Your boiler is currently waiting for a signal from an external control, like your thermostat or programmer, to begin heating.

Low Engineer only

Parts commonly replaced

  • External timer
  • Room thermostat

Related codes

Full explanation for L A
L1

Your boiler has stopped working because it has detected that the water inside is dangerously hot or is not circulating properly.

High Engineer only £150-300

Parts commonly replaced

  • Pump
  • Flow sensor
  • Heat exchanger

Related codes

Full explanation for L1
Showing 61–70 of 74
LCD

Your boiler has detected an internal communication error with the electronic controller that manages the pump and fan, meaning the system cannot start safely.

High Engineer only £200-400

Parts commonly replaced

  • Wiring harness
  • Main control PCB

Related codes

Full explanation for LCD
Low Mains Voltage

Your boiler is receiving insufficient power from your home's electrical supply, which is preventing it from operating correctly.

High Engineer only £100-£200

Parts commonly replaced

  • Electrical supply wiring
  • PCB

Related codes

Full explanation for Low Mains Voltage
NO CH OPERATION

Your boiler is not receiving a signal to turn on the heating, which is usually caused by an external control setting or a simple adjustment rather than a broken internal part.

Medium DIY-safe £0-120

What to check first

  1. Check that the boiler display does not say 'Off' and ensure it is set to the 'Winter' or 'Heating and Hot Water' mode.
  2. Verify that your room thermostat is set higher than the current room temperature and has fresh batteries.
  3. Check your programmer or heating timer to ensure it is in an 'On' period and that your radiator valves are turned up.

Parts commonly replaced

  • Thermostat batteries
  • External Room Thermostat
  • Heating Programmer
Full explanation for NO CH OPERATION
No Water Flow

Your boiler has stopped working because the water pressure is too low or water isn't moving through the system correctly.

High DIY-safe £0-180

What to check first

  1. Check the pressure gauge and use the filling loop to top up the system to 1.0 bar
  2. Bleed all radiators to remove trapped air
  3. Ensure all radiator valves and boiler isolation valves are fully open

Parts commonly replaced

  • External filling loop
  • Water pressure sensor
  • Circulation pump
Full explanation for No Water Flow
Outside Sensor Fault

Your boiler has lost connection with the sensor that measures the temperature outside, meaning it may not heat your home as efficiently as usual.

Low Engineer only £90-160

Parts commonly replaced

  • Outdoor weather compensation sensor
  • Sensor wiring harness
Full explanation for Outside Sensor Fault
Overheat Lockout

Your boiler has detected that it is running too hot and has automatically shut itself down to prevent damage.

High DIY-safe £120-250

What to check first

  1. Ensure all radiator valves are fully open.
  2. Check the boiler pressure gauge and refill to 1.0 bar using the filling loop if low.
  3. Bleed any trapped air from your radiators and top up pressure again if needed.
  4. Reset the boiler using the reset button on the front panel.

Parts commonly replaced

  • NTC Thermistor
  • Pump
  • Heat Exchanger

Related codes

Full explanation for Overheat Lockout
P1

Your boiler has detected that the internal water pressure is too high, causing it to shut down for safety.

High Engineer only £120-250

Parts commonly replaced

  • Pressure Relief Valve
  • Expansion Vessel
  • Pressure Sensor

Related codes

Full explanation for P1
P4

Your boiler has detected that it is overheating internally and has shut itself down to prevent damage to its internal mechanisms.

High Engineer only £150-300

Parts commonly replaced

  • Temperature sensor
  • System pump
  • Heat exchanger

Related codes

Full explanation for P4
PCB Fault

Your boiler's internal computer has suffered a critical failure and can no longer control the heating system safely.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for PCB Fault
Return Thermistor

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

Medium Engineer only £120-220

Parts commonly replaced

  • Return NTC Thermistor
  • Wiring harness

Related codes

Full explanation for Return Thermistor
Showing 71–74 of 74
Return Thermistor Fault

Your boiler has detected an issue with a temperature sensor that monitors the water returning from your radiators, preventing the system from heating up safely.

High Engineer only £110-190

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring Harness
Full explanation for Return Thermistor Fault
Room Thermostat Fault

Your heating hasn't come on because your wall thermostat has run out of power and cannot send a signal to the boiler.

High DIY-safe £5-15

What to check first

  1. Locate your wall-mounted room thermostat or portable controller.
  2. Remove the battery compartment cover.
  3. Replace the old batteries with a new set of high-quality alkaline batteries (usually AA or AAA).
  4. Check if the display turns on and wait a few minutes for it to reconnect to the boiler.

Parts commonly replaced

  • AA Batteries
  • AAA Batteries
Full explanation for Room Thermostat Fault
Spare PCB Not Set

Your boiler's computer brain has been replaced or reset and needs to be told which specific model it is controlling before it can start working.

High Engineer only £80-160

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
Full explanation for Spare PCB Not Set
Too Many Restarts

Your boiler has failed to start up or stay on several times in a row, so it has safely locked itself to prevent potential issues.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Spark generator

Related codes

Full explanation for Too Many Restarts
Status & diagnostic codes

10 operating states & engineer diagnostics

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

05 Status Your boiler has detected that the water temperature is rising too quickly or is too hot, which has caused it to shut down for safety reasons. 12 Status Your boiler has detected an issue with the flame ignition process, meaning it is currently unable to light and provide heat or hot water. 15 Status Your boiler is struggling to detect a flame and cannot start the ignition process properly, meaning you currently have no heating or hot water. 18 Status Your boiler has detected an issue with the gas supply or the internal ignition system, preventing it from safely starting up. 24 Status Your boiler has detected a problem with the fan that moves air and gases through the system, which is preventing it from lighting safely. 30 Status Your boiler is struggling to communicate with its internal control system, causing it to stop heating to prevent any potential issues. 54 Status Your boiler is working exactly as it should and is simply indicating that it has reached your desired heating temperature. H n Status Your boiler is undergoing a routine maintenance interval and is reminding you that it is due for its annual service. Service Due Diagnostic Your boiler is simply reminding you that its annual safety check and maintenance visit is now due. Service Required Diagnostic Your boiler is simply reminding you that it has been over a year since its last professional health check and it is now due for an annual service.
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