Ideal i-mini2 C24 Fault codes & diagnostics

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

Combi Natural Gas 24 kW 2022-present
GC Numbers 47-387-1547-387-1647-387-17
Download the Ideal i-mini2 C24 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. 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.
23 High 3 Medium 1 Low
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
47-387-15 i-mini2 c24 2022–present
47-387-16 i-mini2 c30 2022–present
47-387-17 i-mini2 c35 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.

Just want the most common Ideal i-mini2 C24 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 27 documented codes

Tap any card for details

F 0t

Your boiler has lost communication with its wall-mounted temperature control, meaning it doesn't know when to turn your heating on or off.

Medium DIY-safe £60-180

What to check first

  1. Check and replace the batteries in your wall-mounted room thermostat
  2. Ensure the thermostat is turned up higher than the current room temperature
  3. Check the wireless receiver on the boiler for any red lights and try the 'pair' button if applicable

Parts commonly replaced

  • Room thermostat batteries
  • Wireless thermostat transmitter
  • Receiver unit

Related codes

Full explanation for F 0t
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 two blue-handled valves or a braided hose) underneath the boiler.
  2. Slowly open both taps until you hear water entering the system.
  3. Watch the pressure gauge and close both taps tightly once the needle reaches 1.5 bar.
  4. Press the 'Reset' button on the front of the boiler to restart it.

Parts commonly replaced

  • Filling loop valves
  • Pressure sensor
  • Expansion vessel

Related codes

Full explanation for F 01
F 02

Your boiler has started to light but the flame has gone out unexpectedly, often because the gas supply is interrupted or a sensor cannot detect the fire.

High DIY-safe £100-£280

What to check first

  1. Check that your gas emergency control valve is open and you have credit on your gas meter.
  2. Check if other gas appliances, like a cooker, are working to confirm gas supply.
  3. Reset the boiler by turning the mode knob to the 'RESET' position and holding for two seconds.

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Ignition lead

Related codes

Full explanation for F 02
F 03

Your boiler has detected an issue with the fan, which means it cannot safely exhaust waste gases and has shut down as a precaution.

High Engineer only £250-£450

Parts commonly replaced

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

Related codes

Full explanation for F 03
F 04

Your boiler has lost its ability to measure the temperature of the water leaving the unit, meaning it cannot operate safely and has shut down.

High Engineer only £100-£180

Parts commonly replaced

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

Related codes

Full explanation for F 04
F 04 or L 04

Your boiler's internal sensor that monitors the temperature of the water leaving the unit has stopped working, preventing the system from heating up correctly.

High Engineer only £90-170

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for F 04 or L 04
F 05

Your boiler has detected a problem with the sensor that monitors the temperature of the water returning from your radiators, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for F 05
F 05 or L 05

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, meaning it cannot operate safely or efficiently.

High Engineer only £90-160

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for F 05 or L 05
F 06

Your boiler is having trouble communicating with the external thermometer that checks the weather outside, which can confuse its heating settings.

Low Engineer only £90-180

Parts commonly replaced

  • Outdoor Sensor
  • Sensor Wiring
  • PCB

Related codes

Full explanation for F 06
F 07

Your boiler is not receiving enough electrical power from the grid to operate safely.

Medium Engineer only £0-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • External Voltage Regulator

Related codes

Full explanation for F 07
Showing 11–20 of 27
F 09

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

High Engineer only £280-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for F 09
F 10

Your boiler is unable to create the spark needed to light the gas and start the heating process, meaning it will not fire up.

High Engineer only £140-£240

Parts commonly replaced

  • Spark generator
  • Ignition electrode
  • Wiring harness

Related codes

Full explanation for F 10
F 12

Your boiler has identified that the internal pump, which moves water around your pipes, is stuck or jammed.

High Engineer only £180-£350

Parts commonly replaced

  • Circulation Pump
  • Pump Head
  • Magnetic Filter

Related codes

Full explanation for F 12
F 13

Your boiler's internal pump has stopped working, which means hot water cannot be circulated around your radiators or taps.

High Engineer only £220-£380

Parts commonly replaced

  • Circulating Pump
  • Pump Wiring Harness

Related codes

Full explanation for F 13
F 14

Your boiler has detected that the electricity coming into your home from the national grid is set at too high a voltage, which could damage the internal electronics.

High Engineer only £0-250

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Surge Protector

Related codes

Full explanation for F 14
F 15

Your boiler's internal pump has stopped circulating water, which means your heating and hot water will not work until the component is repaired.

High Engineer only £240-£380

Parts commonly replaced

  • Circulating Pump
  • Pump Wiring Harness

Related codes

Full explanation for F 15
F 16

Your boiler has detected an internal electrical problem with the part that controls gas flow, so it has shut down as a safety precaution.

High Engineer only £220-£380

Parts commonly replaced

  • Gas Valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F 16
F0C

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

Full explanation for F0C
F0U

Your boiler has shut down because it is getting too hot too quickly, usually because the water isn't flowing through the system as it should.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves (TRVs) are fully open to allow water to circulate.
  2. Ensure your boiler pressure is between 1.0 and 1.5 bar on the gauge.
  3. Reset the boiler using the control knob or reset button.

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger (Cleaning/Flushing)
  • Flow and Return Thermistors

Related codes

Full explanation for F0U
L 0C

Your boiler has tried to restart five times in a short period and has locked itself out to prevent further damage.

High Engineer only £100-350

Parts commonly replaced

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

Related codes

Full explanation for L 0C
Showing 21–27 of 27
L 0d

Your boiler has stopped working because its exhaust pipe or drainage tube is likely blocked, preventing it from starting safely.

High DIY-safe £80-220

What to check first

  1. Check the white plastic pipe outside for ice and gently pour warm water over it if frozen.
  2. Inspect the flue terminal on your outside wall for any obstructions like leaves or debris.
  3. Press the 'Reset' button on the boiler control panel once any visible blockages are cleared.

Parts commonly replaced

  • Condensate Trap
  • Spark Electrode
  • Gas Valve

Related codes

Full explanation for L 0d
L 01

Your boiler has got too hot and has shut itself down for safety, meaning you have no heating or hot water until the system cools and is reset.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open to allow water to circulate.
  2. Ensure there is enough water in the system by checking the pressure gauge is between 1 and 1.5 bar; top up if necessary.
  3. Once the boiler has cooled, press and hold the 'Mode/Reset' button for 3 seconds to clear the lockout.

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Heat Exchanger (de-sludge)

Related codes

Full explanation for L 01
L 02

Your boiler has tried to light several times but cannot establish a flame, meaning it has shut down for safety.

High DIY-safe £100-£350

What to check first

  1. Check that your gas emergency control valve is in the 'on' position.
  2. If you have a prepayment gas meter, check that you have sufficient credit.
  3. Press and hold the 'Reset' button for two seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Lead
  • PCB

Related codes

Full explanation for L 02
L 04

Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, causing it to shut down as a safety precaution.

High Engineer only £90-160

Parts commonly replaced

  • Flow Thermistor NTC
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for L 04
L 05

Your boiler has detected a problem with the sensor that monitors the temperature of the water returning from your radiators, preventing it from heating correctly.

High Engineer only £90-160

Parts commonly replaced

  • Return thermistor (NTC sensor)
  • Wiring harness
  • Control box (PCB)

Related codes

Full explanation for L 05
L 06

Your boiler detects a flame when it hasn't actually told the gas valve to open yet, which is a safety conflict.

High Engineer only £120-£350

Parts commonly replaced

  • Flame sensing electrode
  • Gas valve
  • Printed Circuit Board (PCB)

Related codes

Full explanation for L 06
L2

Your boiler has failed to ignite and has locked itself out for safety reasons after multiple unsuccessful attempts to start.

High DIY-safe £100-£350

What to check first

  1. Check that your gas emergency control valve is open and you have credit on your gas meter
  2. Check if other gas appliances in your home, like a hob, are working correctly
  3. Press the 'RESTART' button on the front of the boiler control panel

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Probe
  • Condensate Trap (if blocked)

Related codes

Full explanation for L2
Status & diagnostic codes

6 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

dU Diagnostic Your boiler is currently stuck in a service mode used for maintenance and simply needs to be rebooted to return to normal operation. F9 C Diagnostic Your boiler has lost its internal settings and no longer knows it is supposed to function as a combination boiler providing both heating and hot water. F9 n Diagnostic Your boiler's electronic control board hasn't been properly configured to recognize the type of gas being supplied to your home. F9 SU Diagnostic Your boiler is currently stuck in its startup setup mode and needs to be properly configured before it can provide heating or hot water. oF Diagnostic Your boiler is currently in a setup mode used for programming the control board and is not experiencing an actual operational fault. uP Diagnostic Your boiler is currently in a configuration mode that usually appears when the power is first turned on or after a control board has been replaced.
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.