DIVERTER VALVE IN MID-POSITION FOR SERVICE
Ideal Independent C24 Fault codes & diagnostics
24 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Replaced by: Independent Combi
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Severity at a glance
Each cell = one fault code. Hover to identify.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 |
|---|---|---|
| 47-349-24 | INDEPENDENT COMBI 24 | 2016–present |
| 47-349-27 | INDEPENDENT + COMBI 24 | 2016–present |
| 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 24 documented codes
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F1 Your boiler has stopped working because the water pressure inside the system is too low to operate safely.
Your boiler has stopped working because the water pressure inside the system is too low to operate safely.
What to check first
- Locate the filling loop (usually a silver braided hose with one or two valves underneath the boiler).
- Open the valve(s) slowly to allow mains water into the system while watching the pressure gauge on the front of the boiler.
- Close the valve(s) tightly once the needle reaches the green zone, typically between 1.0 and 1.5 bar.
Parts commonly replaced
- Filling loop
- Pressure relief valve
- Pressure sensor
Related codes
F2 Your boiler's internal computer is having trouble communicating with its configuration settings, meaning it cannot safely start up.
Your boiler's internal computer is having trouble communicating with its configuration settings, meaning it cannot safely start up.
Parts commonly replaced
- Boiler Control Card (BCC)
- Wiring Harness
Related codes
Flame Loss
F3 Your boiler has detected that the internal fan is not spinning correctly, which prevents it from safely venting gases, so it has shut down to protect your home.
Your boiler has detected that the internal fan is not spinning correctly, which prevents it from safely venting gases, so it has shut down to protect your home.
Parts commonly replaced
- Fan assembly
- Wiring harness
- PCB
Related codes
F4 Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside it, causing it to shut down for safety.
Your boiler has stopped working because it is unable to accurately measure the temperature of the water inside it, causing it to shut down for safety.
Parts commonly replaced
- Flow NTC Thermistor
Related codes
Flow Thermistor Fault
F5 Your boiler is struggling to read the temperature of the water returning to it, so it has turned itself off as a precaution to prevent overheating.
Your boiler is struggling to read the temperature of the water returning to it, so it has turned itself off as a precaution to prevent overheating.
Parts commonly replaced
- Return NTC thermistor
- Wiring harness
Related codes
Return Thermistor Fault
F6 Your boiler is struggling to detect the current outdoor temperature, which means it cannot automatically adjust your heating to match the weather outside.
Your boiler is struggling to detect the current outdoor temperature, which means it cannot automatically adjust your heating to match the weather outside.
Parts commonly replaced
- Outside Air Temperature Sensor
Related codes
F7 Your boiler is struggling to operate because the electricity supply from your home is too weak or unstable.
Your boiler is struggling to operate because the electricity supply from your home is too weak or unstable.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Wiring harness
Related codes
PCB UNCONFIGURED OR FAULTY
NEGATIVE DIFFERENTIAL FLOW OR RETURN THERMISTOR FAULT
FLAME LOSS
DIFF GREATER THAN 50°C
L1 Your boiler has lost communication with its internal memory chip, meaning it cannot operate safely until the settings are restored or the component is replaced.
Your boiler has lost communication with its internal memory chip, meaning it cannot operate safely until the settings are restored or the component is replaced.
Parts commonly replaced
- Boiler Control Card (BCC)
- Wiring Harness
Related codes
L2 Your boiler has detected that it is getting too hot or cannot move water through the system, so it has safely shut itself down to prevent damage.
Your boiler has detected that it is getting too hot or cannot move water through the system, so it has safely shut itself down to prevent damage.
Parts commonly replaced
- Central heating pump
- Flow sensor
- NTC thermistor
Related codes
L4 Your boiler has detected that the flame inside has gone out unexpectedly, so it has shut itself down to keep your home safe.
Your boiler has detected that the flame inside has gone out unexpectedly, so it has shut itself down to keep your home safe.
Parts commonly replaced
- Ignition lead
- Electrode assembly
- Gas valve
Related codes
FLOW THERMISTOR FAULT
L5 Your boiler has attempted to restart itself too many times in a short period due to an underlying fault, so it has now locked itself out for safety.
Your boiler has attempted to restart itself too many times in a short period due to an underlying fault, so it has now locked itself out for safety.
Parts commonly replaced
- Printed Circuit Board (PCB)
- Ignition Electrode
- Flame Rectification Probe
Related codes
RETURN THERMISTOR FAULT
L6 Your boiler has detected a flame when it shouldn't be there, so it has safely shut itself down to prevent any risk.
Your boiler has detected a flame when it shouldn't be there, so it has safely shut itself down to prevent any risk.
Parts commonly replaced
- Flame rectification probe
- Printed Circuit Board (PCB)
- Gas valve
Related codes
Boiler has attempted to restart 5 times within 15 minutes
FLAME LOSS