Ferroli Arean Fault codes & diagnostics

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

Combi Natural Gas Discontinued

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
7 Emergency 124 High 17 Medium 28 Low
Just want the most common Ferroli Arean faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 176 documented codes

Tap any card for details

LED / flash-pattern codes
Display Flashing

Your boiler is struggling to start because the water pressure inside your heating system has dropped too low.

High DIY-safe £80-120

What to check first

  1. Locate the filling loop, which is usually a small silver braided hose or a plastic key underneath the boiler.
  2. Open the valves on the filling loop slowly to let water into the system.
  3. Watch the pressure gauge on the front of the boiler and close the valves once the needle reaches 1.5 bar.

Parts commonly replaced

  • Pressure gauge
  • Filling loop
  • Pressure relief valve

Related codes

Full explanation for Display Flashing
Red LED on/Flashing

Your boiler has safety-locked itself to prevent damage or because it failed to light three times in a row.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is active (e.g., check other gas appliances)
  2. Locate the reset knob/button on the control panel
  3. Turn the knob to 'Reset' for 2 seconds and release to see if the boiler restarts

Parts commonly replaced

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

Related codes

Full explanation for Red LED on/Flashing
Digital codes
10

Your boiler is not turning on because it isn't receiving a signal that a flame has successfully lit.

High DIY-safe £120-250

What to check first

  1. Check that your gas meter supply valve and the gas isolation valve near the boiler are both fully open.
  2. Check if other gas appliances in your home, such as a gas hob, are working to confirm gas supply.
  3. Locate the Reset button on the boiler control panel and press it for a few seconds to attempt a restart.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead

Related codes

Full explanation for 10
12

Your boiler is not starting because it is unable to ignite its flame.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 12
13

Your boiler is trying to start but the flame is not igniting, meaning you currently have no heating or hot water.

High DIY-safe £120-250

What to check first

  1. Check that your gas supply is working by testing another gas appliance like a hob
  2. Ensure the gas isolation valve near the boiler is turned to the fully open position
  3. Press the RESET button on the front control panel once to attempt a restart

Parts commonly replaced

  • Ignition electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for 13
14

Your boiler is trying to start but the flame isn't catching, meaning you currently have no heating or hot water.

High DIY-safe £120-250

What to check first

  1. Check that your gas meter control valve is turned to the 'on' position.
  2. Ensure any gas isolation valves located underneath the boiler are fully open.
  3. Press the reset button on the boiler control panel once to attempt a restart.

Parts commonly replaced

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

Related codes

Full explanation for 14
15

Your boiler has stopped working because it cannot light the internal flame needed to heat your water or radiators.

High DIY-safe £120-250

What to check first

  1. Check that your gas supply is on by ensuring other gas appliances like a hob are working.
  2. Verify the gas isolation valve near your boiler and at the main meter are both in the open position.
  3. Press the RESET button on the boiler control panel once to see if it restarts.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition transformer

Related codes

Full explanation for 15
16

Your boiler is failing to ignite the flame needed to heat your home's water and radiators.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

Full explanation for 16
17

Your boiler is failing to ignite because it isn't receiving enough gas to produce a flame.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 17
18

Your boiler is failing to light because it cannot detect a flame, meaning you currently have no heating or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition transformer

Related codes

Full explanation for 18
Showing 11–20 of 176
19

Your boiler is not receiving gas or cannot ignite, meaning you currently have no heating or hot water until the issue is cleared.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 19
20

Your boiler is trying to start but the flame is not catching, likely because it is not receiving a gas supply.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 20
21

Your boiler is currently unable to ignite, which means it cannot provide heat or hot water because it is not sensing a flame.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 21
23

Your boiler is not receiving enough gas or failing to ignite, meaning it cannot produce heat or hot water.

High DIY-safe £120-250

What to check first

  1. Check that your gas meter emergency control valve is turned to the fully open position.
  2. Verify the gas isolation valve located underneath the boiler is open.
  3. Check if other gas appliances in your home, such as a gas hob, are working to confirm gas supply.
  4. Press the 'Reset' button on the boiler control panel once.

Parts commonly replaced

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

Related codes

Full explanation for 23
24

Your boiler is not firing up because it cannot detect a flame, meaning you currently do not have any heating or hot water.

High DIY-safe £100-£250

What to check first

  1. Check that your gas supply is turned on at the meter and the boiler isolation valve.
  2. Ensure you have credit on your gas meter if you are on a prepayment plan.
  3. Press the Reset button on the front of the boiler once to see if it clears the fault.
  4. Check if other gas appliances in your home, like a cooker, are working to confirm gas is reaching the property.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 24
25

Your boiler is trying to start but cannot detect a flame, meaning it is currently unable to provide heating or hot water.

High DIY-safe £120-250

What to check first

  1. Check that your gas supply is turned on at the meter and the boiler isolation valve.
  2. Ensure any other gas appliances are working to rule out a main gas supply issue.
  3. Press the reset button on your boiler control panel once to see if it restarts.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead

Related codes

Full explanation for 25
26

Your boiler is currently unable to ignite, meaning it cannot produce heating or hot water for your home.

High DIY-safe £120-250

What to check first

  1. Check that your gas supply is active by turning on a gas hob or checking other appliances
  2. Ensure the gas isolation valve near the boiler and the main gas meter are fully open
  3. Press the physical RESET button on the boiler control panel once to attempt a restart

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for 26
30

Your boiler has temporarily paused operation because a sensor detected that a temperature or pressure reading has briefly drifted outside of its normal operating limits.

Low Engineer only £90-180

Parts commonly replaced

  • NTC temperature sensor
  • System pressure sensor
  • Printed circuit board

Related codes

Full explanation for 30
31

Your boiler has temporarily paused because it detected a slight inconsistency in its internal readings, but it will restart automatically once things return to normal.

Low Engineer only

Parts commonly replaced

  • Temperature sensor
  • Wiring harness

Related codes

Full explanation for 31
32

Your boiler is temporarily pausing its operation until its internal temperature or pressure readings return to a safe and normal level.

Low Engineer only

Parts commonly replaced

  • NTC Temperature sensor
  • System pressure switch
  • Main circuit board (PCB)

Related codes

Full explanation for 32
Showing 21–30 of 176
34

Your boiler has temporarily paused because it detected a temperature or pressure reading outside of its standard operating limit, and it will attempt to restart itself once conditions stabilise.

Low Engineer only £90-180

Parts commonly replaced

  • NTC Temperature Sensor
  • Pressure Sensor
  • Control PCB

Related codes

Full explanation for 34
35

Your boiler has detected a temporary issue and stopped working as a safety precaution, but it should restart itself automatically once the internal temperature or pressure returns to normal.

Low Engineer only £90-180

Parts commonly replaced

  • NTC temperature sensor
  • Central heating pump

Related codes

Full explanation for 35
36

Your boiler has detected a temporary issue with its internal heat levels or water flow and has paused itself while it waits for conditions to return to normal.

Low Engineer only £100-200

Parts commonly replaced

  • Temperature sensor
  • Pump
  • Circuit board
Full explanation for 36
37

Your boiler has temporarily paused because it detected an operating value, such as water pressure or pressure levels, outside of its normal range, but it should restart itself once conditions stabilise.

Low Engineer only £90-180

Parts commonly replaced

  • Pressure sensor
  • System pressure gauge
  • Expansion vessel

Related codes

Full explanation for 37
38

Your boiler is temporarily pausing because it has detected a reading outside of its normal operating parameters, but it should restart itself once conditions return to normal.

Medium DIY-safe

What to check first

  1. Check the system pressure gauge and top up to 1.5 bar if low
  2. Ensure all radiator valves are open to allow correct circulation
  3. Wait for the boiler to cool down if it has recently overheated
  4. Press the reset button if the boiler does not restart automatically

Parts commonly replaced

  • NTC Sensor
  • System Pressure Sensor
  • Main Control Board

Related codes

Full explanation for 38
39

Your boiler has detected a temporary inconsistency in its operating temperature, so it has paused itself to stay safe and will likely restart automatically once it cools down.

Low Engineer only £100-250

Parts commonly replaced

  • NTC temperature sensor
  • System bypass valve
  • Central heating pump

Related codes

Full explanation for 39
40

Your boiler has detected a temporary temperature issue and is pausing itself to prevent damage, but it should restart automatically once cooled.

Medium DIY-safe £100-200

What to check first

  1. Check that all radiator valves are fully open
  2. Check the system pressure is between 1 and 1.5 bar
  3. Wait for the boiler to cool and restart automatically
  4. Ensure there is no air trapped in the system by bleeding radiators

Parts commonly replaced

  • NTC temperature sensor
  • Pump
  • Primary heat exchanger

Related codes

Full explanation for 40
41

Your boiler has detected a temporary operating temperature anomaly and has turned itself off briefly to protect the system before it should automatically restart.

Low Engineer only £90-180

Parts commonly replaced

  • NTC temperature sensor
  • System bypass valve
  • Central heating pump

Related codes

Full explanation for 41
42

Your boiler has temporarily paused itself because a sensor reading momentarily went outside its normal limit, but will restart automatically once conditions stabilize.

Low Engineer only £90-180

Parts commonly replaced

  • NTC temperature sensor
  • System bypass valve
  • Central heating pump

Related codes

Full explanation for 42
43

Your boiler has detected that the water inside the system has become too hot and has temporarily turned itself off to cool down, which it should fix automatically.

Medium Engineer only £120-250

Parts commonly replaced

  • NTC temperature sensor
  • Pump
  • Heat exchanger

Related codes

Full explanation for 43
Showing 31–40 of 176
45

Your boiler has detected a temporary temperature mismatch and has paused itself to prevent damage, but it should restart automatically once it cools down.

Low Engineer only £100-250

Parts commonly replaced

  • NTC temperature sensor
  • System bypass valve
  • Central heating pump

Related codes

Full explanation for 45
46

Your boiler has detected a temporary temperature spike and has safely paused itself to let the internal parts cool down.

Medium DIY-safe

What to check first

  1. Check that all radiator valves are open to ensure water flow
  2. Monitor the boiler to see if it restarts automatically once cooled
  3. If the fault persists, try a manual reset of the appliance
  4. Check if the system pressure is between 1 and 1.5 bar on the gauge

Parts commonly replaced

  • NTC Sensor
  • Pump
  • Primary Heat Exchanger

Related codes

Full explanation for 46
47

Your boiler has detected a temporary flow issue and has performed a brief safety pause to reset itself automatically.

Low Engineer only £80-150

Parts commonly replaced

  • Water pressure sensor
  • System pump
  • Flow switch

Related codes

Full explanation for 47
49

Your boiler has switched itself off because it got too hot and needs time to cool down before it can safely restart.

High DIY-safe £120-280

What to check first

  1. Turn the boiler off and allow it to cool for 20 minutes
  2. Ensure all radiator valves are fully open to allow water to circulate
  3. Check that your system pressure is between 1 and 1.5 bar
  4. Press the Reset button on the control panel

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger (Cleaning or Replacement)

Related codes

Full explanation for 49
50

Your boiler has shut down because a sensor has detected that the water inside the heating circuit has reached an unsafely high temperature.

High DIY-safe £120-250

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1 and 1.5 bar
  3. Reset the boiler using the reset button once the unit has cooled down

Parts commonly replaced

  • Overheat Thermostat
  • Central Heating NTC Sensor
  • Circulation Pump

Related codes

Full explanation for 50
51

Your boiler has sensed that the temperature inside the unit is too low and has triggered a safety mode to prevent the pipes from freezing.

Medium DIY-safe £90-180

What to check first

  1. Ensure the central heating system is switched on at the programmer.
  2. Carefully increase the room thermostat setting to encourage the boiler to fire up.
  3. If the boiler is in a very cold location like a garage, safely use a heater nearby to raise the ambient temperature around the unit.

Parts commonly replaced

  • Frost thermostat
  • NTC temperature sensor

Related codes

Full explanation for 51
88° C

Your boiler has detected that the water inside the system has become dangerously hot and has shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Pump
  • Diverter valve
  • Heat exchanger
  • Limit thermostat

Related codes

Full explanation for 88° C
100° C

Your boiler has detected that it is running too hot and has automatically turned itself off for safety.

High Engineer only £150-300

Parts commonly replaced

  • Overheat thermostat
  • Central heating pump
  • PCB

Related codes

Full explanation for 100° C
114

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

High DIY-safe £0-160

What to check first

  1. Locate the filling loop (usually a silver braided hose with small valves under the boiler).
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Watch the pressure gauge and close the valves when the needle reaches between 1 and 1.5 bar.
  4. Reset the boiler to clear the fault code.

Parts commonly replaced

  • Water pressure switch
  • Filling loop valve
  • Expansion vessel

Related codes

Full explanation for 114
A LED 1

Your boiler has lost all power and is effectively switched off, preventing it from heating your home or water.

High DIY-safe £80-200

What to check first

  1. Check that the main boiler isolation switch (usually a fused spur nearby) is turned on.
  2. Inspect your home's consumer unit (fuse box) to see if a trip switch or RCD has flicked to the off position.
  3. Check if the fuse within the boiler's local connection unit has blown and replace it if necessary.

Parts commonly replaced

  • Fuses
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for A LED 1
Showing 41–50 of 176
A LED 2

Your boiler is failing to detect that you have turned on a hot water tap, so it is choosing not to heat the water for your shower or kitchen taps.

High Engineer only £120-220

Parts commonly replaced

  • DHW flow meter
  • Turbine sensor

Related codes

Full explanation for A LED 2
A LED 4

Your boiler has stopped providing hot water because it is having trouble reading the water temperature correctly.

High Engineer only £120-200

Parts commonly replaced

  • DHW NTC sensor
  • Wiring harness

Related codes

Full explanation for A LED 4
A LED 5

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

High Engineer only £250-400

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for A LED 5
A LED 6

Your boiler has stopped working because it has detected a faulty electrical signal or low water pressure, which prevents it from safely heating your home or water.

High Engineer only £120-250

Parts commonly replaced

  • DHW temperature sensor
  • Pressure switch
  • Limit thermostat

Related codes

Full explanation for A LED 6
A-1

Your boiler is failing to detect any power, meaning it has completely shut down and cannot heat your home or provide hot water.

High DIY-safe £80-150

What to check first

  1. Check your consumer unit (fuse box) to see if the boiler's circuit breaker has tripped.
  2. Check the fused spur switch located near the boiler to ensure it is in the 'on' position.
  3. Check the fuse inside the fused spur switch to see if it has blown.

Parts commonly replaced

  • External fuse
  • Fused spur
  • PCB

Related codes

Full explanation for A-1
A-2

Your boiler is failing to detect that you have turned on a hot water tap, so it is choosing not to heat the water for your shower or taps.

High Engineer only £120-220

Parts commonly replaced

  • DHW flow meter sensor
  • Turbine assembly
Full explanation for A-2
A-4

Your boiler has stopped providing hot water because it is having trouble reading the temperature of the water used for your taps.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW NTC sensor
  • Wiring harness

Related codes

Full explanation for A-4
A-5

Your boiler's electronic controller has hit an internal error and is unable to start the heating process correctly.

High Engineer only £250-400

Parts commonly replaced

  • Printed Circuit Board (PCB)
Full explanation for A-5
A-6

Your boiler has stopped working because it is unable to detect essential water pressure or temperature readings, likely due to a faulty sensor or low water levels.

High Engineer only £120-250

Parts commonly replaced

  • DHW NTC sensor
  • System pressure switch
  • Limit thermostat
Full explanation for A-6
A01

Your boiler is failing to light the flame needed to produce heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for A01
Showing 51–60 of 176
A02

Your boiler has detected a flame signal even though it is supposed to be turned off, which is a significant safety precaution error.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flame rectification electrode
  • Gas valve
  • PCB

Related codes

Full explanation for A02
A03

Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or overheating.

High Engineer only £120-250

Parts commonly replaced

  • Pump
  • System filter
  • Heat exchanger
  • NTC thermistor

Related codes

Full explanation for A03
A04

Your boiler has detected an issue with its exhaust system multiple times, so it has safely shut itself down to prevent any unsafe gases from building up.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue temperature sensor
  • Fan assembly
  • Printed Circuit Board

Related codes

Full explanation for A04
A05

Your boiler has stopped working because the mechanical fan responsible for clearing exhaust gases is not responding correctly.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

Full explanation for A05
A06

Your boiler has tried to light the burner several times but failed, so it has turned itself off to stay safe.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for A06
A41

Your boiler has lost its connection to the component that monitors water flow, meaning it cannot safely trigger the heating or hot water to start.

High Engineer only £120-220

Parts commonly replaced

  • Flow NTC sensor
  • Wiring loom
  • Main PCB
Full explanation for A41
B LED 1

Your boiler has lost all power and is completely shut down, likely due to a blown internal fuse or an issue with your home's electrical supply.

High Engineer only £120-220

Parts commonly replaced

  • Internal fuse
  • Printed Circuit Board (PCB)
Full explanation for B LED 1
B LED 2

Your boiler believes a hot water tap is running continuously, which is preventing it from heating your home normally.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW Flowmeter
  • Flow Switch

Related codes

Full explanation for B LED 2
B LED 3

Your boiler is currently idle because it is not receiving a signal from your thermostat or timer to start heating.

High DIY-safe £80-150

What to check first

  1. Check your room thermostat and ensure the temperature set point is higher than the current room temperature.
  2. Verify that your external timer or programmer is set to 'On' and that the current time is set correctly.
  3. Replace the batteries in your wireless thermostat if applicable to ensure it is communicating with the receiver.

Parts commonly replaced

  • Room thermostat
  • Digital programmer
  • Wiring centre
Full explanation for B LED 3
B LED 4

Your boiler has stopped working because it cannot correctly sense its own temperature, likely due to a loose wire or a faulty temperature probe.

High Engineer only £120-200

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Loom

Related codes

Full explanation for B LED 4
Showing 61–70 of 176
B LED 6

Your boiler has stopped working because it has detected a problem with either its water pressure, internal temperature sensors, or safety thermostats.

High Engineer only £120-250

Parts commonly replaced

  • Central heating flow sensor
  • Limit thermostat
  • Pressure switch

Related codes

Full explanation for B LED 6
B-1

Your boiler has lost its power supply, which could be due to a tripped switch, a disconnected plug, or a blown fuse.

High DIY-safe £80-150

What to check first

  1. Check that your boiler's power switch or fused spur is switched to the ON position.
  2. Check your home's main consumer unit (fuse box) to see if the boiler's circuit breaker has tripped.
  3. Ensure the plug or fused spur connection is securely connected and that the fuse inside the spur has not failed.

Parts commonly replaced

  • Fused spur
  • Internal PCB fuse
  • Power cable
Full explanation for B-1
B-2

Your boiler is correctly registering that a hot tap is turned on and is preparing to provide hot water.

Low Engineer only

Parts commonly replaced

  • DHW Flow switch
  • Flowmeter
Full explanation for B-2
B-3

Your boiler is currently switched on but is not receiving a signal from your thermostat or timer to tell it to start heating your home.

High DIY-safe £80-150

What to check first

  1. Check your room thermostat is set to a temperature higher than the current room temperature.
  2. Ensure your heating programmer or clock is set to 'On' and the current time is correctly displayed.
  3. Replace the batteries in your wireless thermostat if applicable, then wait a few minutes for a signal to establish.

Parts commonly replaced

  • External room thermostat
  • Time clock / Programmer
  • Wiring harness
Full explanation for B-3
B-4

Your boiler has stopped working because it cannot correctly detect the water temperature or believes the internal system is becoming dangerously hot.

High Engineer only £120-220

Parts commonly replaced

  • Central heating temperature sensor
  • NTC thermistor

Related codes

Full explanation for B-4
B-5

Your boiler is currently in a brief, automatic rest period and will restart heating water once the cooling process finishes.

Low Engineer only

Related codes

Full explanation for B-5
B-6

Your boiler has stopped working because it has detected an issue with its water pressure or internal temperature monitoring systems.

High Engineer only £120-250

Parts commonly replaced

  • Central Heating Temperature Sensor
  • Pressure Switch
  • Limit Thermostat

Related codes

Full explanation for B-6
Boiler lockout

Your boiler has stopped working because it couldn't light the internal flame after several attempts, so it has purposefully locked itself for safety.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve
  • PCB

Related codes

Full explanation for Boiler lockout
Boiler sooting

Your boiler is not burning fuel efficiently, which is causing a dangerous build-up of soot and significantly increases the risk of carbon monoxide poisoning.

Emergency Engineer only £120-250

Parts commonly replaced

  • Burner assembly
  • Gas valve
  • Flue gaskets
Full explanation for Boiler sooting
Showing 71–80 of 176
Burner fails to ignite

Your boiler is trying to start but the flame is not catching, meaning you currently have no heating or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Air pressure switch
  • Fan unit
  • Flow temperature sensor

Related codes

Full explanation for Burner fails to ignite
Burner goes out

Your boiler is struggling to keep the flame lit because it is either blocked by internal dirt or not receiving enough gas to stay running safely.

High Engineer only £120-250

Parts commonly replaced

  • Gas valve
  • Burner assembly
  • Flow temperature sensor

Related codes

Full explanation for Burner goes out
C LED 7

Your boiler has detected an issue with the airflow system which prevents it from safely igniting and providing heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Venturi nozzle

Related codes

Full explanation for C LED 7
C RY2

Your boiler has detected an internal electrical fault with a component that controls the system's operation, causing it to stop working to prevent further damage.

High Engineer only £150-300

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for C RY2
C RY4

Your boiler has detected an internal communication error between its safety sensors and the fan, preventing it from safely starting up.

High Engineer only £120-250

Parts commonly replaced

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

Related codes

Full explanation for C RY4
C-7

Your boiler has detected an issue with the airflow system which prevents it from igniting safely, so it has shut down to protect your home.

High Engineer only £150-250

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Venturi/tubing

Related codes

Full explanation for C-7
C-RY2

Your boiler has detected an internal electrical communication error, meaning it has safely shut itself down to prevent potential damage.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for C-RY2
C-RY4

Your boiler has detected an issue with the airflow system, which is preventing it from safely lighting to provide heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Air pressure switch
  • Fan assembly
  • Wiring harness

Related codes

Full explanation for C-RY4
Condensate in boiler

Your boiler is struggling to process internal moisture correctly, often because it is set to a low temperature or the fuel flow is not adjusted properly.

High Engineer only £120-250

Parts commonly replaced

  • Condensate trap
  • Gas valve
  • Burner seal

Related codes

Full explanation for Condensate in boiler
E01

Your boiler is failing to light the flame needed to produce heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for E01
Showing 81–90 of 176
E02

Your boiler has detected that it is overheating and has automatically switched itself off to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Safety thermostat
  • Central heating pump
  • System filter
  • Diverter valve

Related codes

Full explanation for E02
E03

Your boiler has detected an issue with the airflow system, which is preventing it from lighting safely so it has locked itself to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Air pressure switch
  • Venturi
  • Flue fan

Related codes

Full explanation for E03
E04

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the filling loop, which is a silver braided hose or a small valve with a lever near the pipes under the boiler.
  2. Open the valve(s) to allow cold mains water to enter the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and restart the boiler.

Parts commonly replaced

  • Pressure relief valve
  • Pressure transducer
  • Filling loop

Related codes

Full explanation for E04
E05

Your boiler has stopped working because it is unable to accurately measure the temperature of the water used for your radiators.

High Engineer only £120-200

Parts commonly replaced

  • Central heating flow sensor
  • Wiring harness

Related codes

Full explanation for E05
E06

Your boiler is struggling to accurately measure the temperature of the water used for your taps and shower, meaning it will likely fail to provide hot water.

Medium Engineer only £120-200

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC temperature sensor

Related codes

Full explanation for E06
F1

Your boiler is attempting to start but cannot light the internal flame, meaning you currently have no heating or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate siphon

Related codes

Full explanation for F1
F01

Your boiler is failing to ignite the flame needed to produce heat or hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB
Full explanation for F01
F2

Your boiler has detected a flame even though it is not supposed to be running, which is a safety lockout to prevent potential issues.

Emergency Engineer only £150-300

Parts commonly replaced

  • Ionization electrode
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F2
F3

Your boiler has switched itself off because it is detecting a blockage or a lack of water movement that is causing the internal temperature to rise too quickly.

High Engineer only £120-250

Parts commonly replaced

  • Central heating pump
  • Flow sensor
  • Plate heat exchanger

Related codes

Full explanation for F3
F4

Your boiler has switched off because the water pressure inside your heating system has dropped too low to operate safely.

High DIY-safe

What to check first

  1. Locate the filling loop (a silver flexible hose) underneath the boiler.
  2. Open the valves at both ends of the hose to let mains water enter the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches between 1 and 1.5 bar, then close both valves tightly.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Pressure gauge

Related codes

Full explanation for F4
Showing 91–100 of 176
F5

Your boiler has stopped working because it cannot detect that the internal fan, which is essential for safely venting exhaust gases, is spinning correctly.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

Full explanation for F5
F07

Your boiler has detected that the exhaust gases are getting too hot, so it has shut down as a safety precaution to prevent overheating.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flue gas temperature sensor
  • Heat exchanger
  • Main PCB
Full explanation for F07
F8

Your boiler is trying to start but failing to light the internal flame, resulting in a temporary lockout to keep your home safe.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for F8
F9

Your boiler has lost its connection to the component that controls the gas supply, meaning it cannot start up to provide heat or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • Main control PCB

Related codes

Full explanation for F9
F10

Your boiler is struggling to detect the flow of water through the system, meaning it cannot safely turn on your heating or hot water.

High Engineer only £120-200

Parts commonly replaced

  • Flow sensor
  • Wiring loom

Related codes

Full explanation for F10
F10 ÷ F22

Your boiler's internal computer is experiencing a system error and cannot communicate with the unit's controls, causing the boiler to stop working for safety.

High Engineer only £250-450

Parts commonly replaced

  • Main Control PCB
  • Wiring harness

Related codes

Full explanation for F10 ÷ F22
F10-F22

Your boiler’s internal computer is experiencing a temporary glitch or a major software failure, meaning it cannot safely control the heating or hot water systems.

High Engineer only £200-450

Parts commonly replaced

  • Main printed circuit board (PCB)
  • Control module

Related codes

Full explanation for F10-F22
F11

Your boiler has stopped working because it cannot correctly read the temperature of the water returning to it, likely due to a loose wire or a faulty sensor.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for F11
F13

Your boiler has stopped working because it cannot properly detect the temperature of the exhaust gases leaving the unit, usually due to a faulty sensor or a loose wire.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for F13
F14

Your boiler is struggling to detect the flow of water because a sensor that monitors the system is not working correctly, which will stop your heating and hot water from functioning.

High Engineer only £120-220

Parts commonly replaced

  • Flow sensor
  • Wiring loom

Related codes

Full explanation for F14
Showing 101–110 of 176
F15

Your boiler has detected that the internal fan responsible for safely venting exhaust gases is not spinning correctly or has lost its connection.

High Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

Full explanation for F15
F25

The boiler's internal computer has encountered a glitch or memory error, preventing it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Main control board (PCB)

Related codes

Full explanation for F25
F26

Your boiler has tried to light the burner several times but failed, meaning it cannot provide heat or hot water until the ignition system is looked at.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Control board (PCB)
Full explanation for F26
F30

Your boiler has stopped working because it is unable to accurately measure the temperature of the water being sent to your radiators, causing it to shut down for safety.

High Engineer only £120-200

Parts commonly replaced

  • Central heating flow NTC sensor
  • Wiring harness

Related codes

Full explanation for F30
F31

Your boiler has stopped working because it is unable to correctly read the temperature of the water being sent to your radiators, causing it to shut down for safety.

High Engineer only £120-220

Parts commonly replaced

  • Central heating flow NTC sensor
  • Wiring harness
Full explanation for F31
F34

Your boiler has detected that the electricity supply coming from your wall is unstable, meaning it is either too weak or too strong to run safely.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for F34
F35

Your boiler is struggling because the electricity supply coming into your home is not stable or consistent enough for it to operate.

Medium Engineer only £100-250

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for F35
F36

Your boiler's main brain is struggling to communicate with internal components, which has caused the system to shut down for safety.

High Engineer only £250-450

Parts commonly replaced

  • Main Control Board (PCB)
  • Wiring harness

Related codes

Full explanation for F36
F37

Your boiler has stopped working because the amount of water inside your heating system has dropped too low.

High DIY-safe £80-150

What to check first

  1. Locate the external filling loop, which is a silver braided hose connecting two pipes underneath the boiler.
  2. Open the small valve on the filling loop to allow water into the system while watching the pressure gauge.
  3. Close the valve firmly once the needle on the pressure gauge reaches the green zone, typically between 1.0 and 1.5 bar.

Parts commonly replaced

  • Pressure sensor
  • Filling loop
  • Pressure relief valve

Related codes

Full explanation for F37
F39

Your boiler is struggling to detect the current outdoor temperature, which means it cannot automatically adjust your heating to match the weather outside.

Low Engineer only £100-£180

Parts commonly replaced

  • External weather compensation sensor
  • Wiring loom

Related codes

Full explanation for F39
Showing 111–120 of 176
F40

Your boiler has detected that the water pressure inside your heating system is dangerously high, causing it to shut down to prevent internal damage.

High DIY-safe £80-150

What to check first

  1. Check that the silver filling loop valves are tightly closed.
  2. Bleed water from a radiator using a bleed key to reduce the pressure.
  3. Monitor the pressure gauge to ensure it returns to between 1 and 1.5 bar.
  4. Press the reset button once the pressure is stabilised.

Parts commonly replaced

  • Pressure relief valve
  • Filling loop
  • Expansion vessel

Related codes

Full explanation for F40
F42

Your boiler is currently unable to detect the flow of water because one of its internal sensors has failed, meaning it will not switch on to provide heating or hot water.

High Engineer only £120-220

Parts commonly replaced

  • Flow temperature probe
  • NTC sensor
  • Wiring harness

Related codes

Full explanation for F42
F43

Your boiler is struggling to accurately monitor the temperature of the water circulating back from your radiators, so it has stopped working for safety reasons.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for F43
F44

Your boiler's temperature monitoring system has detected an inaccurate reading, which is causing it to turn itself off to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Return NTC Temperature Sensor
  • Wiring harness
Full explanation for F44
F45

Your boiler has detected a problem with the sensor that monitors the temperature and safety of the exhaust gasses, causing it to stop working to keep you safe.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for F45
F46

Your boiler has detected an issue with the sensor that monitors the path used to vent exhaust gases, causing it to shut down for safety reasons.

Emergency Engineer only £150-250

Parts commonly replaced

  • Flue thermostat
  • Wiring harness
  • PCB

Related codes

Full explanation for F46
F47

Your boiler has lost its connection to an internal sensor, meaning it cannot monitor its own temperature and has shut down for safety.

High Engineer only £120-200

Parts commonly replaced

  • Pressure sensor
  • Wiring harness
  • Main circuit board

Related codes

Full explanation for F47
FH

Your boiler is currently performing a brief automatic self-test to clear any trapped air from the system and will usually resume normal operation on its own after two minutes.

Low DIY-safe

What to check first

  1. Wait for 120 seconds to allow the automated air purge cycle to complete.
  2. Do not turn off or reset the boiler while this light is displayed.
  3. If the code does not disappear after two minutes, check that your system pressure is at the correct level (typically 1-1.5 bar) and top it up if necessary.

Related codes

Full explanation for FH
Green LED on

Your boiler is receiving power and is ready to work, but it hasn't been told to turn on the heating or hot water yet.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up higher than the current room temperature.
  2. Ensure your programmer or heating timer is set to 'ON'.
  3. Turn on a hot water tap to see if the boiler fires up for water demand.

Parts commonly replaced

  • Room thermostat
  • External programmer
  • Piver/Diverter valve
Full explanation for Green LED on
Insufficient system pressure

Your boiler has stopped heating because the water pressure inside the system has dropped too low.

High DIY-safe

What to check first

  1. Locate the filling loop (a silver flexible hose) underneath the boiler or nearby pipework.
  2. Open the valves at both ends of the hose to let water enter the system.
  3. Monitor the pressure gauge on the front of the boiler until it reaches between 1 and 1.5 bar, then securely close both valves.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel

Related codes

Full explanation for Insufficient system pressure
Showing 121–130 of 176
LED 1

Your boiler is not receiving any power, which means it cannot turn on to provide heating or hot water.

High DIY-safe £90-250

What to check first

  1. Check that the boiler's fused spur switch on the wall is in the 'on' position.
  2. Check your consumer unit (fuse box) to see if the circuit breaker for the heating system has tripped.
  3. Check the external plug fuse if the boiler is connected via a standard socket.

Parts commonly replaced

  • Internal fuse
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for LED 1
LED 1 green (0)

Your boiler is currently completely unresponsive because it is not receiving any electrical power.

High DIY-safe £80-150

What to check first

  1. Check that the boiler isolator switch (usually a white switch near the boiler) is set to the ON position.
  2. Check your home's main fuse box (consumer unit) to see if any circuit breakers have tripped.
  3. Locate the fused spur next to the boiler and check if the replaceable fuse inside has blown.

Parts commonly replaced

  • External fuse
  • Fused spur switch
  • Printed Circuit Board (PCB)
Full explanation for LED 1 green (0)
LED 1: 0

Your boiler is not receiving any power, meaning it cannot turn on or provide any heating and hot water.

High DIY-safe £70-180

What to check first

  1. Check if other appliances in your home are working to ensure there isn't a general power cut.
  2. Ensure the boiler's power switch or fused spur on the wall is turned on.
  3. Check your property's main fuse box or consumer unit to see if a circuit breaker has tripped.

Parts commonly replaced

  • External fuse
  • Internal PCB fuse
  • Main PCB
Full explanation for LED 1: 0
LED 2

Your boiler detects water flowing through the system even while the tap is turned off, causing it to run continuously or lock out to prevent overheating.

High Engineer only £120-220

Parts commonly replaced

  • Flow switch
  • DHW flow sensor

Related codes

Full explanation for LED 2
LED 2 (C.H.)

Your boiler mistakenly thinks you are running a hot tap because a sensor is stuck, which is preventing your central heating from turning on.

Medium Engineer only £120-200

Parts commonly replaced

  • DHW Flow switch
  • Flowmeter turbine

Related codes

Full explanation for LED 2 (C.H.)
LED 2 (CH)

Your boiler is currently stuck in hot water mode because it wrongly thinks someone has turned on a tap.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW Flow switch
  • Flowmeter turbine

Related codes

Full explanation for LED 2 (CH)
LED 2 (D.H.W.)

Your boiler is failing to detect when you turn on your hot water tap, so it isn't starting up to warm the water.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW Flow meter
  • Turbine sensor
Full explanation for LED 2 (D.H.W.)
LED 2 (DHW)

Your boiler is failing to detect that you have turned on a hot water tap, meaning it won't fire up to heat the water for your shower or taps.

Medium Engineer only £120-220

Parts commonly replaced

  • DHW flow turbine
  • Flow sensor

Related codes

Full explanation for LED 2 (DHW)
LED 2 yellow (0) [DHW mode]

Your boiler does not realise that you have turned on your hot water tap, so it is failing to heat the water for your shower or kitchen faucet.

High Engineer only £120-220

Parts commonly replaced

  • DHW Flow switch
  • Microswitch

Related codes

Full explanation for LED 2 yellow (0) [DHW mode]
LED 2 yellow (1) [CH mode]

Your boiler has correctly sensed that a hot water tap is running, and this light simply signifies that it is currently preparing to heat your water.

Low Engineer only

Parts commonly replaced

  • DHW Flow Switch
  • Flow Switch Diaphragm
Full explanation for LED 2 yellow (1) [CH mode]
Showing 131–140 of 176
LED 2: 0

Your boiler is not detecting when you turn on a hot tap, meaning you will likely have heating but no hot water.

Medium Engineer only £120-£210

Parts commonly replaced

  • DHW Flowmeter
  • Flow switch
  • Connecting wiring harness

Related codes

Full explanation for LED 2: 0
LED 2: 1

Your boiler thinks a hot water tap is turned on even when all taps are closed, which may prevent your central heating from working.

Medium DIY-safe £90-160

What to check first

  1. Check all hot water taps in the house are fully closed
  2. Ensure there are no dripping taps or leaking hot water pipes
  3. Turn the boiler power off and back on again to reset the sensor

Parts commonly replaced

  • DHW Flowmeter
  • Flow Switch
  • Diverter Valve

Related codes

Full explanation for LED 2: 1
LED 3

Your boiler is working normally and is currently responding to a signal from your thermostat or timer to provide heating or hot water.

Low DIY-safe

What to check first

  1. Check your room thermostat is set to a temperature higher than the current room temperature.
  2. Verify your heating timer or smart controller is set to 'ON' and that the display is active.
  3. Replace the batteries in your room thermostat or wireless controller if applicable.

Parts commonly replaced

  • Room thermostat
  • Programmer/Timer
  • External wiring
Full explanation for LED 3
LED 3 (CH)

Your boiler is currently waiting for a signal from your thermostat or timer to tell it that the house needs heating.

Medium DIY-safe £0-£120

What to check first

  1. Check your room thermostat and ensure it is set to a temperature higher than the current room temperature
  2. Check that your timer or programmer is in the 'ON' position for heating
  3. Replace the batteries in your wireless thermostat if you have one

Parts commonly replaced

  • Room thermostat
  • Programmer/Timer
  • External wiring

Related codes

Full explanation for LED 3 (CH)
LED 3 yellow (0) [CH mode]

Your boiler is currently on standby because your thermostat or timer is not sending a signal to request heating.

Low DIY-safe

What to check first

  1. Check your room thermostat is set to a temperature higher than the current room temperature.
  2. Ensure your programmer or digital timer is switched to the 'ON' position for the heating schedule.
  3. Replace the batteries in your room thermostat if it is a wireless unit.

Parts commonly replaced

  • Room thermostat
  • Programmer/Timer
Full explanation for LED 3 yellow (0) [CH mode]
LED 3: 0

Your boiler is not receiving a signal from your thermostat or timer to turn on the heating.

Low DIY-safe £0-120

What to check first

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

Parts commonly replaced

  • Batteries
  • Room thermostat
  • External programmer/clock
Full explanation for LED 3: 0
LED 4

Your boiler's temperature sensors are signalling that they cannot properly detect or regulate the heat, which is preventing the system from firing up your heating or hot water.

High Engineer only £120-200

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness
Full explanation for LED 4
LED 4 (C.H.)

Your boiler has stopped heating your radiators because it is either detecting an overheating issue or is struggling to communicate with its internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • Central heating temperature sensor
  • Limit thermostat
Full explanation for LED 4 (C.H.)
LED 4 (CH)

Your boiler has detected an issue with its internal temperature sensing, meaning it cannot accurately judge how much to heat your radiators.

High Engineer only £120-220

Parts commonly replaced

  • Central Heating NTC Sensor
  • Wiring harness

Related codes

Full explanation for LED 4 (CH)
LED 4 (D.H.W.)

Your boiler has stopped producing hot water because it has lost contact with or is misreading the temperature sensor that monitors your hot water supply.

High Engineer only £120-220

Parts commonly replaced

  • DHW temperature sensor (NTC)
  • Wiring harness / connection cable
Full explanation for LED 4 (D.H.W.)
Showing 141–150 of 176
LED 4 (DHW)

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

High Engineer only £120-180

Parts commonly replaced

  • DHW NTC thermistor sensor
  • Wiring harness

Related codes

Full explanation for LED 4 (DHW)
LED 4 green (0) [CH mode]

Your boiler has stopped producing heat because it is struggling to accurately read its own internal temperature or has overheated.

High Engineer only £120-220

Parts commonly replaced

  • Central heating NTC temperature sensor
  • Limit thermostat
  • Wiring harness
Full explanation for LED 4 green (0) [CH mode]
LED 4 green (0) [DHW mode]

Your boiler has stopped producing hot water because it believes the internal temperature sensor is either disconnected or reading an dangerously high temperature.

High Engineer only £120-200

Parts commonly replaced

  • DHW NTC Sensor
  • Wiring harness
Full explanation for LED 4 green (0) [DHW mode]
LED 4: 0

Your boiler has detected an issue with the sensor that monitors hot water temperature, which often means the water is getting too hot or the sensor has stopped working.

High Engineer only £90-160

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for LED 4: 0
LED 4: 0 (Central Heating)

Your boiler has stopped working because it thinks it is overheating or it cannot correctly read the temperature sensor for your radiators.

High Engineer only £90-180

Parts commonly replaced

  • Central heating temperature sensor (NTC thermistor)
  • Overheat limit thermostat
  • Wiring harness

Related codes

Full explanation for LED 4: 0 (Central Heating)
LED 5 (CH)

Your boiler is currently in a temporary self-imposed waiting period as part of its normal safety cycle and should restart automatically on its own shortly.

Low DIY-safe

What to check first

  1. Wait for 3 to 5 minutes for the countdown to finish
  2. Check that the room thermostat or programmer is calling for heat
  3. Ensure the boiler pressure is between 1 and 1.5 bar

Parts commonly replaced

  • Control board
  • System sensor

Related codes

Full explanation for LED 5 (CH)
LED 5 (DHW)

Your boiler's electronic control brain is experiencing a persistent internal error that prevents it from providing hot water or heating correctly.

High Engineer only £250-450

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5 (DHW)
LED 5 red (1) [DHW mode]

Your boiler has detected an internal computer error and is currently unable to start, meaning you will likely have no hot water or heating.

High Engineer only £250-400

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5 red (1) [DHW mode]
Showing 151–160 of 176
LED 5: 1

Your boiler's main internal computer has developed a critical electronic failure and can no longer process the startup sequence.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for LED 5: 1
LED 5: 1 (Central Heating)

Your boiler is temporarily pausing between heating cycles and should restart automatically within a few minutes.

Low DIY-safe

What to check first

  1. Wait 3 to 5 minutes for the countdown timer to finish
  2. Check that your room thermostat is turned up
  3. Ensure there is power to the unit and no other fault lights are flashing

Related codes

Full explanation for LED 5: 1 (Central Heating)
LED 6 (C.H.)

Your boiler has stopped working because it cannot detect enough water pressure or is struggling to read the temperature correctly, meaning it has safely shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Central Heating Temperature Sensor
  • Pressure Sensor
  • Limit Thermostat

Related codes

Full explanation for LED 6 (C.H.)
LED 6 (CH)

Your boiler has stopped working because it has detected an issue with its water pressure or internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • Central Heating NTC Sensor
  • Limit Thermostat
  • Pressure Transducer

Related codes

Full explanation for LED 6 (CH)
LED 6 (D.H.W.)

Your boiler has stopped working because it has detected a technical fault related to the water pressure or internal temperature sensors.

High Engineer only £120-250

Parts commonly replaced

  • DHW Sensor
  • Pressure Switch
  • Limit Thermostat

Related codes

Full explanation for LED 6 (D.H.W.)
LED 6 (DHW)

Your boiler has stopped working because it has detected an issue with its water pressure or internal sensors, preventing it from safely heating your home or water.

High DIY-safe £120-250

What to check first

  1. Check the boiler pressure gauge on the front panel; if it is below 1.0 bar, use the filling loop to top it up to between 1.0 and 1.5 bar
  2. Turn the boiler off at the mains for 60 seconds to reset the electronic fault
  3. Turn the boiler back on and observe if the error clears

Parts commonly replaced

  • DHW NTC Sensor
  • Pressure Transducer
  • Limit Thermostat

Related codes

Full explanation for LED 6 (DHW)
LED 6 yellow (0) [CH mode]

Your boiler has detected a faulty temperature reading caused by a sensor issue, which is preventing your central heating from turning on.

High Engineer only £120-200

Parts commonly replaced

  • Central heating NTC temperature sensor
Full explanation for LED 6 yellow (0) [CH mode]
LED 6 yellow (0) [DHW mode]

Your boiler is struggling to detect the temperature of your hot water because of a faulty connection or sensor, which means it will likely stop providing hot water until fixed.

Medium Engineer only £120-180

Parts commonly replaced

  • DHW NTC thermistor sensor
Full explanation for LED 6 yellow (0) [DHW mode]
LED 6: 0

Your boiler has detected an issue that could be caused by low water pressure or a faulty internal sensor, leading to a safety shutdown.

High DIY-safe £90-180

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 too low, use the filling loop to top up the system until the needle reaches the 1.5 bar mark.
  3. Restart the boiler to see if the fault clears; if the pressure is correct and the code remains, you will need an engineer.

Parts commonly replaced

  • D.H.W. Temperature Sensor (NTC)
  • C.H. Limit Thermostat
  • Water Pressure Switch

Related codes

Full explanation for LED 6: 0
Showing 161–170 of 176
LED 6: 0 (Central Heating)

Your boiler has detected low water pressure or a faulty internal sensor, causing the heating system to shut down for safety.

High DIY-safe £90-180

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 below 1 bar, use the filling loop to top up the system with water until it reaches the correct level.
  3. Restart the boiler to see if the fault clears.

Parts commonly replaced

  • Central Heating Temperature Sensor (NTC)
  • Water Pressure Switch
  • Limit Thermostat

Related codes

Full explanation for LED 6: 0 (Central Heating)
LED 7

Your boiler is struggling to breathe safely, so it has shut down to prevent any risks while it is unable to properly clear waste gases.

Emergency Engineer only £150-300

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Venturi tube

Related codes

Full explanation for LED 7
LED 7 green (0)

Your boiler has lost its connection to an internal sensor or controller, meaning it cannot detect the necessary conditions to fire up safely.

High Engineer only £120-220

Parts commonly replaced

  • Wiring harness
  • Main control PCB
Full explanation for LED 7 green (0)
LED 7: 0

Your boiler has detected an issue with the air flow or the internal fan, which means it cannot safely exhaust fumes and has shut down as a precaution.

High Engineer only £120-£350

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube

Related codes

Full explanation for LED 7: 0
LED 8 yellow (0)

Your boiler has detected that it has become too hot and has safely shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Limit thermostat
  • Overheat sensor
  • Pump
  • PCB

Related codes

Full explanation for LED 8 yellow (0)
Low system pressure

Your boiler has lost the water pressure it needs to circulate heat around your home, so it has safely shut itself down to prevent damage.

High DIY-safe

What to check first

  1. Locate the external filling loop, which is a small silver flexible hose connected to two valves under the boiler.
  2. Open the valves slowly to allow cold mains water to enter the system until the pressure gauge on the front of the boiler reaches between 1 and 1.5 bar.
  3. Close both valves tightly and ensure the flexible hose is disconnected if required by your specific installation.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Expansion vessel

Related codes

Full explanation for Low system pressure
No burner ignition

Your boiler is failing to light the internal flame needed to produce heat and hot water.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • PCB

Related codes

Full explanation for No burner ignition
Radiators cold in winter

Your boiler is failing to circulate heat to your radiators, likely because the internal pump is stuck or the system is failing to detect the correct temperature.

High Engineer only £180-350

Parts commonly replaced

  • Central heating pump
  • Flow temperature sensor (NTC)
  • Pump capacitor

Related codes

Full explanation for Radiators cold in winter
RL2/RLX (not energised)

Your boiler has detected a loose or disconnected internal electrical wire, which is preventing it from safely communicating with its internal components.

High Engineer only £120-200

Parts commonly replaced

  • Wiring harness
  • PCB
Full explanation for RL2/RLX (not energised)
Showing 171–176 of 176
RY2

Your boiler's electronic control system is failing to activate its internal switching mechanism, which is preventing your heating and hot water from turning on.

High Engineer only £150-300

Parts commonly replaced

  • Main PCB
  • Relay module

Related codes

Full explanation for RY2
RY2 Not Energised

Your boiler is failing to detect a request for hot water or heating, preventing it from starting up correctly.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Flow switch
  • Wiring harness

Related codes

Full explanation for RY2 Not Energised
RY2: not energised

Your boiler has detected an internal electrical component that isn't receiving power, preventing the system from starting up.

High Engineer only £120-280

Parts commonly replaced

  • Main Control Board
  • Wiring Harness
  • Relay

Related codes

Full explanation for RY2: not energised
RY4

Your boiler has detected an issue with its internal airflow system, which is preventing it from safely starting up.

High Engineer only £120-220

Parts commonly replaced

  • Air pressure switch
  • Fan assembly
  • Control PCB

Related codes

Full explanation for RY4
RY4 Not Energised

Your boiler is failing to start because it cannot confirm that the air circulation inside is safe, causing it to lock itself to prevent an unsafe condition.

High Engineer only £120-250

Parts commonly replaced

  • Air pressure switch
  • Venturi
  • Flue fan

Related codes

Full explanation for RY4 Not Energised
RY4: not energised

Your boiler has detected that a safety air switch is not in the correct position for the system to start up safely.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube

Related codes

Full explanation for RY4: not energised