Common problems guide

The most common Ikon 40-50 CI problems

The faults most likely to send a Ikon 40-50 CI into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
6 documented codes
6 most common
2 DIY-safe checks
4 engineer needed

The 6 most common faults

01
Neon 1 not lit High DIY-safe

Your boiler is not receiving power, which could be due to a simple external electricity issue or an internal fuse failure.

What to try first

Check if other appliances in your home have powerEnsure the boiler's isolation switch (fused spur) is turned onCheck your consumer unit (fuse box) to see if a circuit breaker has tripped

Est. cost
£90-280
Parts
Internal PCB fuse, Printed Circuit Board (PCB), External fused spur
Full guide for Neon 1 not lit
02
Neon 2 not lit High DIY-safe

Your boiler has switched itself off because it has gotten too hot, likely due to a circulation issue or a faulty internal sensor.

What to try first

Check that all radiator valves are fully openEnsure your system pressure is at the correct level (usually 1.0 to 1.5 bar)Allow the boiler to cool down and try pressing the manual reset button

Est. cost
£90-190
Parts
Overheat Thermostat, Limit Stat, Control Thermostat
Full guide for Neon 2 not lit
03
F1 High Engineer

Your boiler has lost power internally due to a blown safety fuse on the main control board, which has caused the unit to shut down completely.

Est. cost
£120-280
Parts
Internal Glass Fuse (F1A), Printed Circuit Board (PCB), Fan Motor
Full guide for F1
04
F2 High Engineer

Your boiler has likely stopped working because an internal electrical fuse has blown, often because the pump that moves water around your system has jammed or failed.

Est. cost
£140-£280
Parts
Circulating Pump, F1A Fuse, Printed Circuit Board (PCB)
Full guide for F2
05
Neon 3 not lit High Engineer

Your boiler has detected an issue with the ventilation system and has shut down as a safety precaution to ensure exhaust gases are being cleared correctly.

Est. cost
£120-280
Parts
Fan assembly, Air pressure switch, Venting tubes
Full guide for Neon 3 not lit
06
Neon 4 not lit High Engineer

Your boiler is failing to light the gas flame or cannot detect that it has stayed lit, causing the system to shut down for safety.

Est. cost
£120-350
Parts
Ignition Electrode, Flame Sensing Probe, Gas Valve
Full guide for Neon 4 not lit
Parts most often replaced

on the Ikon 40-50 CI

Internal PCB fusePrinted Circuit Board (PCB)External fused spurOverheat ThermostatLimit StatControl Thermostat

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Ikon shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 6-code list for the Ikon 40-50 CI

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →