Ideal Logic Max Combi Fault codes & diagnostics

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

Combi Natural Gas 24-35 kW 2018-present
GC Numbers 47-349-5647-349-5747-349-5847-349-55
Download the Ideal Logic Max Combi 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.
9 High 1 Medium 7 Unrated
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
47-349-56 LOGIC MAX COMBI C24 2018–present
47-349-57 LOGIC MAX COMBI C30 2018–present
47-349-58 LOGIC MAX COMBI C35 2018–present
47-349-55 LOGIC MAX COMBI C24P 2018–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 Logic Max Combi faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 17 documented codes

Tap any card for details

4.5

Your boiler has detected that the water pressure inside the system is too low to run safely and has switched itself off.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually blue-handled levers) underneath the boiler.
  2. Slowly open the valves until you hear water entering the system.
  3. Watch the pressure gauge and close the valves when the needle reaches 1.5 bar.
  4. Restart the boiler if it does not reset automatically.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 4.5
4.7

Your boiler has stopped working because the internal fan, which safely clears exhaust fumes, is not running correctly.

High Engineer only £280-450

Parts commonly replaced

  • Fan Assembly
  • Main PCB
  • Wiring Loom

Related codes

Full explanation for 4.7
4.8

Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, preventing it from heating your home safely.

High Engineer only £90-160

Parts commonly replaced

  • Flow thermistor (NTC sensor)
  • Wiring harness / connector
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 4.8
4.9

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, likely causing it 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 4.9
4.15

Your boiler is heating your radiators normally, but it is failing to provide hot water when you turn on your taps.

Medium Engineer only £120-£250

Parts commonly replaced

  • Diverter Valve Actuator Motor
  • Diverter Valve Cartridge
  • DHW Flow Turbine

Related codes

Full explanation for 4.15
F4

Your boiler has detected an issue with the sensor that measures the temperature of the water leaving the unit, preventing it from heating your home safely.

High Engineer only £90-180

Parts commonly replaced

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

Related codes

Full explanation for F4
F5

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning from your radiators.

High Engineer only £100-£180

Parts commonly replaced

  • Return Thermistor (NTC)
  • Wiring Harness

Related codes

Full explanation for F5
F7

Your boiler has stopped working because the electrical power coming into your home is at a lower voltage than it needs to operate safely.

High DIY-safe £0-120

What to check first

  1. Check if other appliances in your home are acting strangely or lights are flickering
  2. Contact your electricity network provider to report a potential power supply issue
  3. Once the external power issue is resolved, reset the boiler using the 'RE' dial or button

Parts commonly replaced

  • External mains supply (Power Grid)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F7
L1

Your boiler has switched itself off because the internal water temperature has become too hot, usually caused by a lack of water flow through the system.

High DIY-safe £120-£350

What to check first

  1. Check that your radiator valves are fully open
  2. Ensure your boiler pressure is between 1 and 1.5 bar on the gauge
  3. Reset the boiler by turning the control knob to 'RE' or pressing the reset button

Parts commonly replaced

  • Circulating pump
  • Thermistor (NTC sensor)
  • Main heat exchanger

Related codes

Full explanation for L1
L2

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

High DIY-safe £100-280

What to check first

  1. Check if your gas supply is active by testing another gas appliance like a hob.
  2. If you have a prepay meter, ensure you have sufficient credit.
  3. In freezing temperatures, check if the external condensate pipe has frozen.
  4. Reset the boiler by turning the mode knob to 'RE' and back to your desired setting.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Ignition Lead
  • Ionisation Probe

Related codes

Full explanation for L2
Status & diagnostic codes

2 operating states & engineer diagnostics

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

F9 Diagnostic Your boiler’s internal control board has lost its configuration or is brand new and hasn't been programmed yet to tell it which model it is. P1 Diagnostic Your boiler is displaying a service setting notification to run the pump at maximum speed, which usually indicates an installation or maintenance mode rather than a dangerous mechanical failure.
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