Ferroli iBoiler 24 Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2019-present

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 48 High 2 Medium 1 Low
Just want the most common Ferroli iBoiler 24 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 52 documented codes

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A01

Your boiler has failed to light, which means you currently have no heating or hot water because the system cannot create a flame.

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is turned on at the meter
  2. Check if other gas appliances, like a hob, are working correctly
  3. Press and hold the 'R' or reset button for 2-3 seconds
  4. Check that the condensate pipe outside hasn't frozen in cold weather

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ignition PCB

Related codes

Full explanation for A01
A02

Your boiler is failing to detect a flame when it tries to start, likely due to a faulty ignition component or an internal electrical error.

High Engineer only £120-£350

Parts commonly replaced

  • Ignition electrode
  • Detection electrode
  • Printed Circuit Board (PCB)
  • Electrode wiring harness

Related codes

Full explanation for A02
A03

Your boiler has stopped working because it has detected that it is overheating, often caused by a lack of water movement or air trapped inside the unit.

High DIY-safe £120-280

What to check first

  1. Check that the central heating valves under the boiler are fully open
  2. Ensure your radiator valves are turned on and not blocked
  3. Try bleeding your radiators to remove any trapped air from the system
  4. Check the boiler pressure gauge and top up to 1.5 bar if it is low

Parts commonly replaced

  • Circulation Pump
  • Central Heating Temperature Sensor (NTC)
  • High Limit Thermostat

Related codes

Full explanation for A03
A04

Your boiler has shut down for safety because it has detected repeated problems with how exhaust gases are being cleared from the system.

High Engineer only £120-£350

Parts commonly replaced

  • Air pressure switch
  • Fan assembly
  • Flue venting components

Related codes

Full explanation for A04
A05

Your boiler has stopped working because the internal fan used to clear waste gases is not spinning or communicating correctly with the system.

High Engineer only £180-350

Parts commonly replaced

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

Related codes

Full explanation for A05
A06

Your boiler is struggling to light or keep its flame lit because it isn't receiving enough gas to stay running safely.

High DIY-safe £100-£250

What to check first

  1. Check that your gas emergency control valve (usually by the meter) is fully open
  2. If you have a pre-payment meter, check that you have sufficient credit and that the meter hasn't locked out
  3. Check if other gas appliances, such as a hob, are working correctly to rule out a wider gas supply issue
  4. Reset the boiler by pressing the 'reset' button for 1 second

Parts commonly replaced

  • Gas Valve
  • Ignition Electrode
  • Ionisation Probe

Related codes

Full explanation for A06
A09

Your boiler has detected a problem with how it controls the gas flow, meaning it cannot ignite safely to provide heat or hot water.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Wiring Harness
  • Main Control Board (PCB)

Related codes

Full explanation for A09
A14

Your boiler has shut down because it has detected a problem with how exhaust gases are being cleared from the flue pipe.

Emergency Engineer only £120-350

Parts commonly replaced

  • Flue pressure switch
  • Fan assembly
  • Flue seals
  • Venting pipes

Related codes

Full explanation for A14
A15

Your boiler has stopped working because it has detected a recurring problem with how it vents exhaust gases or takes in fresh air.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan

Related codes

Full explanation for A15
A16

Your boiler has detected a communication problem with the gas flow control, meaning it cannot safely ignite to provide heating or hot water.

High Engineer only £160-£320

Parts commonly replaced

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

Related codes

Full explanation for A16
Showing 11–20 of 52
A23

Your boiler's internal computer has become confused and is using the wrong settings for your specific model.

High Engineer only £120-350

Parts commonly replaced

  • Main PCB
  • Display Board

Related codes

Full explanation for A23
A24

Your boiler's internal computer has become confused or has been programmed with the wrong settings, meaning it cannot operate safely.

High Engineer only £90-280

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Control Card

Related codes

Full explanation for A24
A41

Your boiler has lost its connection with a internal smart sensor that monitors water flow, causing the system to stop working for safety.

High Engineer only £90-180

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Sensor wiring harness

Related codes

Full explanation for A41
A42

Your boiler is struggling to accurately measure how much water is moving through the system, which is preventing it from heating up correctly.

High Engineer only £120-£210

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness
  • Main circuit board (PCB)

Related codes

Full explanation for A42
A54 – A55 – A63

Your boiler's internal computer has encountered a critical communication error and cannot control the heating or hot water safely.

High Engineer only £250-£450

Parts commonly replaced

  • Main PCB (AGC01)
  • Wiring Harness

Related codes

Full explanation for A54 – A55 – A63
A61

Your boiler's internal computer has developed a technical fault and can no longer control the system safely.

High Engineer only £250-£450

Parts commonly replaced

  • Main PCB (ABM03B Control Board)
  • Wiring harness

Related codes

Full explanation for A61
A62

Your boiler has developed a communication fault between its internal computer and the gas control system, meaning it cannot safely ignite to provide heat or hot water.

High Engineer only £180-450

Parts commonly replaced

  • Gas Valve
  • Main PCB (Printed Circuit Board)
  • Wiring Harness

Related codes

Full explanation for A62
A63 / A64 / F66

Your boiler's main internal computer has developed a fault and can no longer communicate with or control the appliance system components correctly.

High Engineer only £250-£450

Parts commonly replaced

  • ABM03B Main PCB
  • Control Board Wiring Loom

Related codes

Full explanation for A63 / A64 / F66
A64

Your boiler has locked itself out because the reset button has been pressed too many times in a short period while trying to clear another fault.

High DIY-safe £0-120

What to check first

  1. Turn the boiler's electrical power switch off at the wall spur.
  2. Wait for at least 30 seconds to allow the internal memory to clear.
  3. Turn the power back on and wait for the boiler to reboot.

Parts commonly replaced

  • No parts usually required for A64
  • PCB (if software freeze occurs)

Related codes

Full explanation for A64
Boilers

Your boiler has detected a general internal fault that is preventing it from heating your water or radiators.

High DIY-safe £100-£280

What to check first

  1. Locate the reset button on the control panel
  2. Press and hold the reset button for 5 seconds
  3. Wait for the boiler to restart and check if the code clears

Parts commonly replaced

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

Related codes

Full explanation for Boilers
Showing 21–30 of 52
DOMIcondens HE 26 C

Your boiler's internal computer has detected that the exhaust gas temperature is too high, causing the system to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Flue gas sensor (NTC)
  • Heat exchanger cleaning kit
  • Main PCB

Related codes

Full explanation for DOMIcondens HE 26 C
F04

Your boiler's internal computer has lost its configuration settings and no longer knows how to operate the heating system correctly.

High Engineer only £100-280

Parts commonly replaced

  • Main PCB
  • Parameter Key

Related codes

Full explanation for F04
F05

Your boiler has detected a problem with how it disposes of exhaust fumes, causing it to shut down for safety.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan
  • Flue Baffle

Related codes

Full explanation for F05
F07

Your boiler has detected that a key safety sensor is stuck in the wrong position, preventing the fan from starting up safely.

High Engineer only £120-240

Parts commonly replaced

  • Air pressure switch
  • Fan assembly
  • Venturi tube

Related codes

Full explanation for F07
F07 – F14 – A07

Your boiler has detected that the exhaust gases are getting too hot and has shut down as a safety precaution to prevent internal damage.

High Engineer only £120-350

Parts commonly replaced

  • Flue NTC sensor
  • Main Heat Exchanger
  • Gas valve

Related codes

Full explanation for F07 – F14 – A07
F08 – A08

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

High DIY-safe £100-280

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1 and 1.5 bar on the gauge
  3. Perform a reset by pressing the 'R' or 'Reset' button

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger (if scaled)

Related codes

Full explanation for F08 – A08
F09 – A09

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 your radiator valves are open to allow water to flow
  2. Ensure your system water pressure is between 1 and 1.5 bar on the gauge
  3. Try resetting the boiler using the 'R' or reset button once the unit has cooled down

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger
  • Temperature Sensor (NTC)

Related codes

Full explanation for F09 – A09
F10

Your boiler's internal temperature sensor has stopped communicating with the main control board, preventing the system from heating up your water safely.

High Engineer only £90-160

Parts commonly replaced

  • NTC Delivery Sensor
  • Wiring Harness Connector

Related codes

Full explanation for F10
F10 – A10

Your boiler's internal sensor that detects water movement has stopped working properly, meaning the system cannot safely heat your home or water.

High Engineer only £120-220

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for F10 – A10
F11

Your boiler has lost its connection to the temperature sensor for your hot water, meaning the unit cannot accurately heat the water for your taps and showers.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW Temperature Sensor (NTC Thermistor)
  • Wiring Harness

Related codes

Full explanation for F11
Showing 31–40 of 52
F11 – A11

Your boiler has stopped working because it cannot accurately measure the temperature of the water returning from your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Return temperature sensor (NTC thermistor)
  • Sensor wiring harness

Related codes

Full explanation for F11 – A11
F12

Your boiler is struggling to detect the temperature of your water, which usually means you won't have any hot water available at your taps.

High Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC Sensor
  • Sensor Wiring Harness

Related codes

Full explanation for F12
F13

Your boiler's internal temperature sensor has failed or has a wiring fault, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness

Related codes

Full explanation for F13
F13 – A13

Your boiler has detected an issue with the sensor that monitors the temperature of the exhaust fumes, causing the system to shut down for safety.

High Engineer only £120-£200

Parts commonly replaced

  • Flue gas NTC sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for F13 – A13
F14

Your boiler's internal thermometer has stopped working correctly, which means the system cannot safely monitor the temperature of the water flowing to your radiators.

High Engineer only £90-160

Parts commonly replaced

  • Flow temperature NTC sensor
  • Wiring harness

Related codes

Full explanation for F14
F15

Your boiler has stopped working because the fan that removes waste gases cannot spin properly or its speed is not being detected.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Main PCB

Related codes

Full explanation for F15
F34

Your boiler has detected that the electricity supply from the mains is too low for it to operate safely.

High Engineer only £100-350

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • External Voltage Stabiliser

Related codes

Full explanation for F34
F35

Your boiler has detected an issue with the quality or consistency of the incoming electricity supply from the power grid.

Medium Engineer only £90-250

Parts commonly replaced

  • Electronic Control Board (PCB)
  • External Surge Protector

Related codes

Full explanation for F35
F37

Your boiler has detected that the water pressure in the system is too low for it to operate safely.

High DIY-safe £80-160

What to check first

  1. Locate the filling loop (a flexible silver hose) underneath or near the boiler
  2. Slowly open the small valve or valves on the loop until you hear water flowing
  3. Watch the pressure gauge and close the valves once it reaches between 1.0 and 1.5 bar

Parts commonly replaced

  • Water pressure switch
  • Filling loop
  • Expansion vessel

Related codes

Full explanation for F37
F39

Your boiler has lost connection with its outdoor temperature sensor, causing it to lose track of the weather outside.

Low Engineer only £90-160

Parts commonly replaced

  • External weather compensation probe
  • Sensor wiring

Related codes

Full explanation for F39
Showing 41–50 of 52
F41

Your boiler has sensed a very sudden and excessive rise in temperature, causing it to shut down to prevent internal damage.

High Engineer only £120-450

Parts commonly replaced

  • Pump
  • Diverter Valve
  • Heat Exchanger

Related codes

Full explanation for F41
F42 – A42

Your boiler has detected an unusual temperature reading that suggests a sensor fault, causing the system to shut down for safety.

High Engineer only £90-180

Parts commonly replaced

  • Heating temperature sensor (NTC thermistor)
  • Wiring harness

Related codes

Full explanation for F42 – A42
F43

Your boiler has stopped to prevent it from overheating because water isn't moving through the system properly or there is trapped air inside.

High DIY-safe £80-250

What to check first

  1. Check that your system pressure is between 1 and 1.5 bar on the pressure gauge
  2. Bleed your radiators to remove any trapped air pockets
  3. Ensure all radiator valves and isolation valves under the boiler are fully open

Parts commonly replaced

  • Circulation pump
  • Heating flow sensor
  • Automatic air vent

Related codes

Full explanation for F43
F50

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

High Engineer only £250-£400

Parts commonly replaced

  • DBM23B Printed Circuit Board (PCB)

Related codes

Full explanation for F50
F51

Your boiler's main internal computer has developed a fault and can no longer control the heating system correctly.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB (Control Board)
  • DBM23B Controller

Related codes

Full explanation for F51
F52

Your boiler is having trouble detecting how much water is moving through the system because a sensor has developed a fault.

High Engineer only £120-190

Parts commonly replaced

  • Flow sensor
  • NTC sensor wiring harness

Related codes

Full explanation for F52
F56 – A56

Your boiler's internal computer is having trouble setting the correct balance of gas and air needed to burn fuel safely and efficiently.

High Engineer only £120-300

Parts commonly replaced

  • Gas valve
  • Flame sensing electrode
  • Main PCB
Full explanation for F56 – A56
F61 – A61

Your boiler's internal computer brain has developed an electronic fault and can no longer control the heating and hot water.

High Engineer only £280-450

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control AGC01 Unit

Related codes

Full explanation for F61 – A61
F66

Your boiler has detected an internal communication error or a potential electronics failure within its main control board.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for F66
F67

Your boiler’s main control board has detected an internal electronic error and needs to be reset.

High DIY-safe £180-350

What to check first

  1. Locate the reset button on the boiler control panel
  2. Press and hold the reset button for 5 seconds
  3. Wait for the boiler to complete its restart cycle

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

Full explanation for F67
Showing 51–52 of 52
F68 – A68

Your boiler's computer memory card has stopped communicating with the main control board, preventing the system from operating correctly.

High Engineer only £120-280

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Main Control Board (PCB)

Related codes

Full explanation for F68 – A68
OPTIMAX HE PLUS 38C

Your boiler has failed to ignite, meaning it cannot light the gas to provide heating or hot water.

High DIY-safe £120-300

What to check first

  1. Check if your gas supply is turned on and other gas appliances are working
  2. Press the 'Reset' button on the boiler control panel
  3. If you have a prepaid gas meter, check that you have remaining credit

Parts commonly replaced

  • Ignition electrode
  • Ionisation probe
  • Gas valve

Related codes

Full explanation for OPTIMAX HE PLUS 38C