Ferroli i25 Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2017 onwards
GC Number 47-267-64
Download the Ferroli i25 manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

The fault code is already on your display

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

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 17 High
Versions & GC numbers

Which version do you have?

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

GC number Appliance (register name) Produced
47-267-64 i25 2017–present

Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.

Just want the most common Ferroli i25 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 18 documented codes

Tap any card for details

A01

Your boiler has failed to light the flame, which means you currently have no heating or hot water.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to confirm your gas supply is on.
  2. If it is a freezing day, ensure your external condensate pipe is not frozen and blocked.
  3. Press the 'Reset' button on the boiler control panel to attempt a restart.

Parts commonly replaced

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

Related codes

Full explanation for A01
A02

Your boiler thinks a flame is burning even though it is supposed to be turned off, which causes it to shut down for safety.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation Electrode
  • Flame Sensing Cable
  • Main PCB

Related codes

Full explanation for A02
A03

Your boiler has switched itself off because it has detected that the water inside has become dangerously hot or a temperature sensor has failed.

High Engineer only £90-180

Parts commonly replaced

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

Related codes

Full explanation for A03
A06

Your boiler is failing to keep the flame lit after it starts up, which is usually caused by an issue with the gas supply or a blocked internal part.

High Engineer only £120-280

Parts commonly replaced

  • Gas valve
  • Electrode
  • Condensate trap
  • PCB

Related codes

Full explanation for A06
A09

Your boiler has detected an issue with the fuel supply component that controls the gas flow, meaning it cannot safely start your heating or hot water.

Emergency Engineer only £150-300

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • PCB

Related codes

Full explanation for A09
A15

Your boiler is struggling to clear exhaust gases safely, so it has shut itself down to prevent any risk.

High Engineer only £150-250

Parts commonly replaced

  • Air pressure switch
  • Venturi
  • Flue fan assembly
  • Pressure sensing tubes

Related codes

Full explanation for A15
A16

Your boiler has detected an issue with the valve that controls the flow of gas, meaning it cannot safely start up to provide heating or hot water.

High Engineer only £180-350

Parts commonly replaced

  • Gas valve
  • Wiring harness
  • PCB

Related codes

Full explanation for A16
A23

Your boiler's computer system has detected a settings error that prevents it from starting up correctly.

High Engineer only £150-300

Parts commonly replaced

  • Main control board (PCB)
  • EEPROM chip

Related codes

Full explanation for A23
A24

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

High Engineer only £100-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)

Related codes

Full explanation for A24
F07

Your boiler has stopped working because it cannot properly detect the flow of air and exhaust gases through the system.

High Engineer only £120-280

Parts commonly replaced

  • Air Pressure Switch
  • Flue Fan
  • Venturi Tube

Related codes

Full explanation for F07
F10

Your boiler has stopped working because it is unable to accurately measure the temperature of the water being sent to your radiators or taps.

High Engineer only £120-220

Parts commonly replaced

  • NTC delivery sensor
  • Wiring harness

Related codes

Full explanation for F10
F11

Your boiler's internal thermometer that monitors the temperature of the water leaving the unit has stopped working, meaning the system has shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • NTC Flow Sensor
  • Wiring Loom

Related codes

Full explanation for F11
F34

Your boiler is failing to start because it is not receiving enough consistent electrical power from your home's mains supply.

High Engineer only £100-250

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for F34
F35

Your boiler is struggling to read the stability of the incoming electricity supply, which is preventing it from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Main printed circuit board (PCB)

Related codes

Full explanation for F35
F37

Your boiler has stopped working because the water pressure inside the system has dropped too low and needs topping up.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath the boiler.
  2. Slowly open the small valve handles until you hear water entering the system.
  3. Watch the pressure gauge and close both valves firmly once it reaches 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Water pressure switch
  • Expansion vessel

Related codes

Full explanation for F37
F43

Your boiler has switched itself off because the water inside is getting too hot too quickly, usually because the water isn't moving through the pipes properly or there is trapped air.

High DIY-safe £120-£350

What to check first

  1. Check that your central heating valves and radiator valves are fully open
  2. Bleed your radiators to remove any trapped air from the system
  3. Ensure the system water pressure is between 1.0 and 1.5 bar on the gauge
  4. Reset the boiler by pressing the 'Reset' button

Parts commonly replaced

  • Central heating pump
  • Automatic air vent
  • Main heat exchanger (if scaled up)

Related codes

Full explanation for F43
F50

Your boiler's internal computer has detected a serious electronic error and has shut down as a safety precaution.

High Engineer only £250-£450

Parts commonly replaced

  • DBM32B Printed Circuit Board (PCB)
  • Earth Wiring Harness

Related codes

Full explanation for F50
F51

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

High Engineer only £250-£450

Parts commonly replaced

  • DBM32B Printed Circuit Board (PCB)
  • Earth wiring loom

Related codes

Full explanation for F51
Boiler cover options

Avoid the next call-out bill

Monthly cover means no unexpected bills when your boiler breaks down.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.