Ideal INDEPENDENT C35 Fault codes & diagnostics

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

Combi Natural Gas 2010-2016 Discontinued
GC Number 47-348-70
Download the Ideal INDEPENDENT C35 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 11 High 2 Medium 1 Low
Fault codes

All 15 documented codes

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5 Boiler Resets in 15 minutes

Your boiler has shut itself down five times in a short period, which means the safety system is repeatedly blocking it from running to prevent potential damage or a safety hazard.

High Engineer only £150-350

Parts commonly replaced

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

Related codes

Full explanation for 5 Boiler Resets in 15 minutes
BCC Activation Fault

Your boiler's internal computer is struggling to communicate with a secondary plug-in component, preventing the system from starting safely.

High Engineer only £150-300

Parts commonly replaced

  • Boiler Control Card (BCC)
  • Wiring harness

Related codes

Full explanation for BCC Activation Fault
BCC Fault

Your boiler is experiencing a communication error with its internal computer, meaning it cannot properly read its own programming and has safely shut down to prevent incorrect operation.

High Engineer only £150-300

Parts commonly replaced

  • Boiler Control Card
  • Wiring harness

Related codes

Full explanation for BCC Fault
c0

Your boiler has lost communication with its electronic control system, meaning it cannot start up safely.

High Engineer only £150-300

Parts commonly replaced

  • BCC (Boiler Control Card)
  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for c0
c2

Your boiler's electronic memory card is not being recognised, which prevents the system from starting up safely.

High Engineer only £150-300

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Main PCB
Full explanation for c2
False Flame Lockout

Your boiler has detected a flame when it shouldn't be burning, so it has safely shut itself off to prevent a potential hazard.

Emergency Engineer only £150-300

Parts commonly replaced

  • Flame rectification probe
  • Gas valve
  • Printed Circuit Board (PCB)
Full explanation for False Flame Lockout
Fan Fault

Your boiler has detected a problem with its internal fan and has shut down as a safety precaution, meaning you will not have any heating or hot water.

High Engineer only £250-£450

Parts commonly replaced

  • Fan assembly
  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for Fan Fault
Flame Loss

Your boiler has detected that the flame inside has gone out unexpectedly and it cannot stay alight, so it has safely shut itself down to prevent gas from building up.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap
  • Flame rectification probe

Related codes

Full explanation for Flame Loss
Flow Thermistor

Your boiler's temperature sensor is providing faulty readings, causing the system to stop operating as it cannot safely monitor how hot the water is getting.

High Engineer only £120-220

Parts commonly replaced

  • Flow NTC Thermistor
  • Wiring harness

Related codes

Full explanation for Flow Thermistor
L2

Your boiler has locked out because it either failed to ignite or detected a blockage in the pipe that removes waste water.

High DIY-safe £90-£180

What to check first

  1. Locate the plastic condensate pipe running from the bottom of your boiler to the outside wall or a drain.
  2. Check if the outdoor section of the pipe is frozen during cold weather by pouring warm (not boiling) water over it.
  3. Reset the boiler using the reset button once you are sure the pipe is clear and unfrozen.

Parts commonly replaced

  • Condensate trap
  • Ignition electrode
  • Gas valve

Related codes

Full explanation for L2
Low Mains Voltage

Your boiler is struggling because the electricity supply coming into your home is weaker than the level required to operate the unit safely.

Medium Engineer only £120-250

Parts commonly replaced

  • PCB
  • Wiring harness
Full explanation for Low Mains Voltage
Low Water Pressure

Your boiler has stopped working because the water level 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 one or two taps on the loop until you hear water flowing.
  3. Watch the pressure gauge on the screen until it reaches 1.5 bar, then close the taps tightly.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for Low Water Pressure
Outside Sensor Failure

Your boiler is struggling to detect the outdoor temperature, so it is running on a default setting instead of adjusting automatically to the weather.

Low Engineer only £120-200

Parts commonly replaced

  • Outside temperature sensor
  • Wiring loom/connection
Full explanation for Outside Sensor Failure
Return Thermistor

Your boiler is struggling to read the temperature of the water returning from your radiators, which prevents it from heating your home efficiently.

Medium Engineer only £120-220

Parts commonly replaced

  • Return NTC Thermistor
  • Wiring harness

Related codes

Full explanation for Return Thermistor
Unconfigured PCB

The computer brain of your boiler has not been told which specific model it is installed in, so it cannot safely start the system.

High Engineer only £120-200

Parts commonly replaced

  • Electronic Control Board (PCB)
Full explanation for Unconfigured PCB