Ferroli Domiproject Fault codes & diagnostics

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

Combi Natural GasLPG 24-32 kW 2006-2016 Discontinued

Replaced by: Ferroli Modena

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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 Domiproject 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 the flame, which means you currently have no heating or hot water.

High DIY-safe £100-£280

What to check first

  1. Check that your gas supply is turned on and other gas appliances are working
  2. Press the Reset button on the boiler control panel for 3 seconds
  3. Ensure the condensate pipe (outside white plastic pipe) isn't frozen if it is cold outside

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PCB (Control Board)

Related codes

Full explanation for A01
A02

Your boiler is failing to start because it cannot detect a flame, likely due to a faulty ignition sensor or an internal control board issue.

High Engineer only £120-£350

Parts commonly replaced

  • Ionisation electrode
  • Ignition cable
  • Printed Circuit Board (PCB)

Related codes

Full explanation for A02
A03

Your boiler has overheated because water isn't moving through the system correctly or a temperature sensor has failed.

High DIY-safe £90-220

What to check first

  1. Check that your system pressure is between 1 and 1.5 bar on the pressure gauge
  2. Bleed all radiators to remove trapped air that might be blocking circulation
  3. Ensure all radiator valves and the boiler isolation valves are fully open
  4. Press the 'Reset' button on the boiler control panel

Parts commonly replaced

  • Heating temperature sensor (NTC)
  • Circulation pump
  • Overheat thermostat

Related codes

Full explanation for A03
A04

Your boiler has shut down because it has detected a recurring issue with how it clears exhaust fumes safely.

High Engineer only £120-£350

Parts commonly replaced

  • Air pressure switch
  • Flue fan
  • PCB (Control board)
  • Venting seals

Related codes

Full explanation for A04
A05

Your boiler has stopped working because the fan that removes waste gases cannot spin or start properly.

High Engineer only £180-£350

Parts commonly replaced

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

Related codes

Full explanation for A05
A06

Your boiler is trying to light but cannot keep the flame burning because it isn't receiving enough gas or the gas pressure is too low.

High DIY-safe £120-250

What to check first

  1. Check that your gas emergency control valve is fully open.
  2. If you have a prepaid gas meter, check that you have sufficient credit.
  3. Test another gas appliance, such as a hob, to see if the gas supply to the property is working.
  4. Press the 'Reset' button on the boiler control panel once to see if the fault clears.

Parts commonly replaced

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

Related codes

Full explanation for A06
A09

Your boiler has stopped working because it cannot properly control the flow of gas required for the burner.

High Engineer only £180-£350

Parts commonly replaced

  • Gas valve
  • Main PCB (Control Board)
  • Wiring harness

Related codes

Full explanation for A09
A14

Your boiler has switched itself off because the safety sensors have detected that harmful exhaust gases are not being cleared safely from the flue pipe.

Emergency Engineer only £120-350

Parts commonly replaced

  • Flue pressure switch
  • Fan assembly
  • Venturi tube

Related codes

Full explanation for A14
A15

Your boiler has shut down because it has repeatedly detected an issue with how it clears exhaust fumes, likely due to a persistent air flow problem.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Venturi Tube
  • Fan Assembly

Related codes

Full explanation for A15
A16

Your boiler has detected a problem with the internal gas valve system, preventing it from lighting safely.

High Engineer only £180-350

Parts commonly replaced

  • Gas Valve
  • Wiring Harness
  • Control Board

Related codes

Full explanation for A16
Showing 11–20 of 52
A23

Your boiler's internal computer has been set up with the wrong configuration settings and does not know how to operate correctly.

High Engineer only £90-280

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for A23
A24

Your boiler's internal computer has been set up with the wrong configuration settings, preventing it from operating correctly.

High Engineer only £100-£350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Control panel interface

Related codes

Full explanation for A24
A41

Your boiler has lost its connection to the sensor that monitors water temperature, causing the system to stop working for safety.

High Engineer only £100-£190

Parts commonly replaced

  • Heating flow sensor (NTC)
  • Wiring harness

Related codes

Full explanation for A41
A42

Your boiler has stopped working because it cannot correctly measure the temperature of the water leaving the unit.

High Engineer only £90-160

Parts commonly replaced

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

Related codes

Full explanation for A42
A54 – A55 – A63

Your boiler's main internal computer has developed a serious communication or hardware failure, causing the system to shut down for safety.

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for A54 – A55 – A63
A61

Your boiler's main internal computer has developed a serious software or electrical fault and can no longer control the system.

High Engineer only £280-£450

Parts commonly replaced

  • ABM03B Main PCB (Circuit Board)
  • Wiring Loom

Related codes

Full explanation for A61
A62

Your boiler has stopped working because the internal control board and the gas valve are no longer communicating with each other.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB
  • Gas Valve
  • Wiring Harness

Related codes

Full explanation for A62
A63 / A64 / F66

Your boiler's main internal computer has developed a serious fault and is unable to communicate with its own internal memory or processor.

High Engineer only £250-450

Parts commonly replaced

  • ABM03B Printed Circuit Board (PCB)
  • Main Control Board

Related codes

Full explanation for A63 / A64 / F66
A64

Your boiler has been manually reset too many times in a short period and has now locked itself out for safety.

High Engineer only £100-350

Parts commonly replaced

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

Related codes

Full explanation for A64
Boilers

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

High Engineer only £120-350

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 temperature sensors are reading a very high temperature, causing the system to shut down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Flow temperature sensor
  • Wiring harness
  • Main PCB

Related codes

Full explanation for DOMIcondens HE 26 C
F04

Your boiler's internal computer has been set up with the wrong configuration settings and does not know how to operate correctly.

High Engineer only £90-250

Parts commonly replaced

  • PCB (Main Control Board)

Related codes

Full explanation for F04
F05

Your boiler is having trouble clearing waste gases through the flue, causing it to shut down for safety.

High Engineer only £100-£280

Parts commonly replaced

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

Related codes

Full explanation for F05
F07

Your boiler has detected that an internal air safety switch is stuck in the wrong position, preventing the system from starting its ignition sequence safely.

High Engineer only £120-250

Parts commonly replaced

  • Air pressure switch
  • Venturi tube
  • Fan assembly
  • Control board

Related codes

Full explanation for F07
F08 – A08

Your boiler has become too hot and has shut itself down for safety.

High DIY-safe £120-350

What to check first

  1. Check that your radiator valves are open to allow water to circulate
  2. Ensure your system water pressure is between 1 and 1.5 bar
  3. Wait 15 minutes for the unit to cool down and try the Reset button

Parts commonly replaced

  • Circulation pump
  • Heat exchanger
  • Overheat thermostat

Related codes

Full explanation for F08 – A08
F09 – A09

Your boiler has shut down because it has detected it is getting too hot and has locked out for safety.

High DIY-safe £120-300

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate
  2. Ensure there is enough water pressure indicated on the boiler gauge (usually 1.0 to 1.5 bar)
  3. Attempt to reset the boiler using the control knob or button

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Main heat exchanger

Related codes

Full explanation for F09 – A09
F10

Your boiler's temperature sensor has failed or lost its connection, meaning it can no longer monitor how hot the water is and has shut down as a safety precaution.

High Engineer only £90-160

Parts commonly replaced

  • Central Heating NTC Temperature Sensor
  • Sensor Wiring Harness

Related codes

Full explanation for F10
F10 – A10

Your boiler has detected an issue with the sensor that monitors internal water flow, meaning it cannot safely determine if water is moving through the system.

High Engineer only £120-£250

Parts commonly replaced

  • Flow sensor
  • NTC thermistor
  • Wiring harness

Related codes

Full explanation for F10 – A10
F11

Your boiler's hot water sensor has stopped communicating correctly with the control board, meaning the system cannot accurately monitor the temperature of the water coming out of your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Wiring Harness

Related codes

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

Your boiler has detected an issue with a temperature sensor that measures water returning from your radiators, preventing it from heating correctly.

High Engineer only £90-160

Parts commonly replaced

  • Return NTC Temperature Sensor
  • Sensor Wiring Harness
  • Main PCB

Related codes

Full explanation for F11 – A11
F12

Your boiler is struggling to detect the temperature of your hot water, which usually means it won't provide a steady supply of warm water to your taps.

Medium 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 stopped sending the correct information to the control board, preventing the system from operating safely.

High Engineer only £90-160

Parts commonly replaced

  • Heat exchanger NTC sensor
  • Wiring harness

Related codes

Full explanation for F13
F13 – A13

Your boiler has detected an issue with the sensor that monitors exhaust gases, which has caused the system to shut down for safety.

High Engineer only £100-180

Parts commonly replaced

  • Flue gas probe
  • Wiring harness
  • Control PCB

Related codes

Full explanation for F13 – A13
F14

Your boiler's internal temperature sensor has failed or has a wiring fault, meaning the system cannot safely monitor the water temperature and has shut down as a precaution.

High Engineer only £90-160

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for F14
F15

Your boiler has stopped working because the internal fan, which safely removes waste gases, is either stuck or cannot communicate with the main control board.

High Engineer only £150-£350

Parts commonly replaced

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

Related codes

Full explanation for F15
F34

Your boiler has stopped working because the electrical power coming from your mains supply is too low for it to run safely.

High Engineer only £100-£350

Parts commonly replaced

  • PCB (Printed Circuit Board)
  • External Voltage Stabilizer

Related codes

Full explanation for F34
F35

Your boiler has detected an issue with the quality or stability of your home's incoming electrical supply, causing it to shut down for safety.

High Engineer only £100-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Surge Protector

Related codes

Full explanation for F35
F37

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

High DIY-safe £60-160

What to check first

  1. Check the pressure gauge on the front of the boiler or under the casing.
  2. Locate the external filling loop, which is usually a flexible silver hose with two small valves.
  3. Slowly open the valves to allow water into the system until the gauge reads between 1.0 and 1.5 bar, then close them tightly.

Parts commonly replaced

  • Water pressure switch
  • Filling loop valve
  • Expansion vessel

Related codes

Full explanation for F37
F39

Your boiler has lost signal or is receiving an incorrect reading from the sensor that monitors the outdoor temperature.

Low DIY-safe £70-130

What to check first

  1. Locate the outdoor sensor on your external wall and check for any visible damage or loose wiring.
  2. Turn the boiler power off and back on again to see if the fault clears.
  3. Check if the outdoor sensor has been obstructed or covered by debris.

Parts commonly replaced

  • External temperature probe
  • Wiring harness

Related codes

Full explanation for F39
Showing 41–50 of 52
F41

Your boiler has shut down because the temperature difference between the water going out and coming back is too high, meaning water isn't moving through the system fast enough.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Bleed all radiators to remove trapped air
  4. Reset the boiler using the selector switch

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Temperature NTC Sensors

Related codes

Full explanation for F41
F42 – A42

Your boiler has detected an unusual temperature difference between its internal sensors and has shut down to prevent overheating.

High Engineer only £120-240

Parts commonly replaced

  • NTC Temperature Sensor
  • Internal Wiring Harness
  • Main Heat Exchanger

Related codes

Full explanation for F42 – A42
F43

Your boiler has stopped working because it is getting too hot too quickly, usually because water isn't flowing through the pipes properly or there is trapped air.

High DIY-safe £120-350

What to check first

  1. Check that your radiator valves are open
  2. Bleed all radiators to remove trapped air
  3. Check the central heating pressure gauge and top it up to 1.5 bar if it is low

Parts commonly replaced

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

Related codes

Full explanation for F43
F50

Your boiler's internal computer brain has detected a serious technical failure and can no longer process instructions safely.

High Engineer only £250-£450

Parts commonly replaced

  • DBM23B Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for F50
F51

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

High Engineer only £250-£400

Parts commonly replaced

  • Main PCB (Control Board)
  • DBM23B Controller
Full explanation for F51
F52

Your boiler has detected a problem with internal temperature sensors, meaning it cannot accurately monitor the water heat and has stopped working for safety.

High Engineer only £90-180

Parts commonly replaced

  • Flow NTC Temperature Sensor
  • Sensor Wiring Harness

Related codes

Full explanation for F52
F56 – A56

Your boiler has failed to set its own internal settings correctly or forgot its configuration, which means it cannot operate until it is professionally recalibrated.

High Engineer only £90-180

Parts commonly replaced

  • PCB (Main Circuit Board)
  • Gas Valve
Full explanation for F56 – A56
F61 – A61

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

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for F61 – A61
F66

Your boiler’s main control board has detected an internal electronic failure and can no longer communicate with its own system.

High Engineer only £220-380

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for F66
F67

Your boiler's main control board has encountered an internal electronic error, meaning the computer that runs the system has failed.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

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

Your boiler's internal computer chip has lost connection or has become corrupted, meaning the system cannot safely identify how it should operate.

High Engineer only £120-£350

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Main PCB (Printed Circuit Board)

Related codes

Full explanation for F68 – A68
OPTIMAX HE PLUS 38C

Your boiler has failed to light the flame after several attempts, meaning you currently have no heating or hot water.

High DIY-safe £120-400

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 control panel for 1 second
  3. If you have a prepayment meter, check that you have enough credit

Parts commonly replaced

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

Related codes

Full explanation for OPTIMAX HE PLUS 38C