Ideal Independent COMBI2 C24 Fault codes & diagnostics

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

Combi Natural Gas 2022-present
GC Number 47-387-09
Download the Ideal Independent COMBI2 C24 manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 23 High 2 Medium 1 Low

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
47-387-09 INDEPENDENT COMBI2 C24 2022–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.

All 27 documented codes

Tap any card for details

dU

Your boiler is confused about whether to send hot water to your taps or your radiators because an internal valve is stuck in the middle.

High Engineer only £150-300

Parts commonly replaced

  • Diverter valve cartridge
  • Diverter valve motor
F 0C

Your boiler's hot water sensor is not working correctly, meaning your taps might not get hot or the temperature could be inconsistent.

Medium Engineer only £90-160

Parts commonly replaced

  • DHW Thermistor (NTC sensor)
  • Wiring harness connecting to the sensor

Related codes

F 0t

Your boiler has lost communication with the wall thermostat, meaning it cannot receive the signal to turn your heating on.

Medium DIY-safe £80-220

What to check first

  1. Check if your wall thermostat has run out of batteries and replace them if necessary.
  2. Ensure the thermostat is turned up higher than the current room temperature.
  3. If using a wireless model, ensure the receiver box is powered on and within range of the thermostat.

Parts commonly replaced

  • Thermostat batteries
  • Room thermostat
  • RF Receiver unit

Related codes

F 0U

Your boiler has detected that the water leaving the unit is far too hot compared to the water returning to it, so it has shut down to prevent internal damage.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Heat exchanger

Related codes

F 01

Your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.
  2. Slowly open the small tap(s) on the filling loop to allow water into the system.
  3. Watch the pressure gauge and close the taps once it reaches 1.5 bar, then restart the boiler.

Parts commonly replaced

  • Filling loop
  • Pressure sensor
  • Expansion vessel

Related codes

F 02

Your boiler has stopped working because the flame inside went out and could not be successfully restarted.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap

Related codes

F 03

Your boiler has detected that the internal fan is not working correctly, which prevents it from safely venting gases, so it has shut down to protect your home.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • PCB

Related codes

F 04

Your boiler's temperature sensor is providing incorrect information, causing the system to stop working as a safety precaution since it cannot accurately regulate how hot the water is.

High Engineer only £120-200

Parts commonly replaced

  • Flow thermistor
  • Wiring harness

Related codes

F 05

Your boiler is struggling to accurately measure the temperature of the water returning to it, so it has stopped working as a safety precaution until the faulty sensor is replaced.

High Engineer only £120-200

Parts commonly replaced

  • Return thermistor sensor
  • Wiring harness

Related codes

F 06

Your boiler has lost communication with the weather sensor installed outside your home, so it is temporarily running as if it were a standard system without outdoor temperature compensation.

Low Engineer only £120-200

Parts commonly replaced

  • Outside Temperature Sensor
  • Outdoor Sensor Wiring

Related codes

Showing 11–20 of 27
F 07

Your boiler is not receiving enough electrical power from the grid to operate safely and has shut down as a precaution.

High Engineer only £0-250

Parts commonly replaced

  • Main PCB
  • Voltage Regulator

Related codes

F 09

Your boiler's main control board has suffered an internal electronic failure and is no longer able to manage the heating system.

High Engineer only £280-450

Parts commonly replaced

  • Printed Circuit Board (PCB)

Related codes

F 10

Your boiler is unable to create the spark needed to light the flame, which means your heating and hot water will not work.

High Engineer only £140-£240

Parts commonly replaced

  • Spark Generator
  • Ignition Lead
  • Printed Circuit Board (PCB)

Related codes

F 12

Your boiler has stopped working because the internal pump that moves hot water through your pipes is jammed or stuck.

High Engineer only £180-350

Parts commonly replaced

  • Central Heating Pump
  • Pump Head

Related codes

F 13

Your boiler's internal pump has stopped circulating water, which means the system cannot deliver heat to your radiators.

High Engineer only £250-£450

Parts commonly replaced

  • Circulation Pump
  • Pump head
  • Wiring harness

Related codes

F 14

Your boiler has detected that the electricity supply from the national grid is currently too high for it to operate safely.

High Engineer only £0-350

Parts commonly replaced

  • Main Printed Circuit Board
  • Voltage Regulator

Related codes

F 15

Your boiler has detected a problem with the internal pump, meanining it cannot move heated water around your system to warm your radiators.

High Engineer only £220-£380

Parts commonly replaced

  • Central heating pump
  • Internal pump wiring harness

Related codes

F 16

Your boiler's gas valve is not communicating correctly with the control board, meaning the unit cannot safely manage the flow of fuel to create heat.

High Engineer only £220-£380

Parts commonly replaced

  • Gas Valve
  • Control Lead / Wiring Harness
  • Main PCB

Related codes

F 17

Your boiler's internal pump is unable to circulate water around the system, meaning your heating and hot water will not work.

High Engineer only £220-£380

Parts commonly replaced

  • Central heating pump
  • Internal pump wiring harness

Related codes

F0U

Your boiler has detected that the water leaving the unit is far too hot compared to the water returning to it, so it has shut down to prevent internal damage.

High Engineer only £150-300

Parts commonly replaced

  • Central heating pump
  • System filter
  • Heat exchanger

Related codes

Showing 21–27 of 27
L 0C

Your boiler has temporarily locked itself out because it had to restart five times in a short space of time.

High DIY-safe

What to check first

  1. Switch the boiler off using the power switch or main isolator switch.
  2. Wait for approximately 30 seconds to allow the system to fully reset.
  3. Turn the boiler back on and check if it fires up normally.

Related codes

L 0d

Your boiler has stopped working because it cannot safely get rid of exhaust gases or water waste, so it has shut down to protect your home.

Emergency Engineer only £120-250

Parts commonly replaced

  • Condensate trap
  • Flue seal
  • Fan assembly
  • Air pressure switch

Related codes

L 01

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

High Engineer only £150-£300

Parts commonly replaced

  • Pump
  • System filter
  • Heat exchanger
  • NTC sensor

Related codes

L 02

Your boiler is failing to light the flame needed to generate heat and has safely shut down to prevent gas buildup.

High Engineer only £120-250

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead

Related codes

L 04

Your boiler has lost the ability to read the temperature of the water flowing through it, so it has safely shut down to prevent overheating.

High Engineer only £120-200

Parts commonly replaced

  • Flow Thermistor/NTC Sensor
  • Wiring Harness

Related codes

L 05

Your boiler is struggling to accurately detect the temperature of the water returning to it, so it has shut down to prevent potential overheating.

High Engineer only £120-200

Parts commonly replaced

  • Return thermistor
  • Wiring harness

Related codes

L 06

Your boiler thinks a flame is present before the gas has even started flowing, which is a safety conflict that prevents the system from starting.

High Engineer only £120-£350

Parts commonly replaced

  • Ionisation probe
  • Gas valve
  • Main PCB

Related codes

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