Ideal Classic Slimline FF 330 360 Fault codes & diagnostics

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

Regular Natural Gas 8.8-17.6 kW 1994-2005 Discontinued
GC Numbers 41-391-7641-391-77

Replaced by: Logic Heat

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Ideal Classic Slimline FF 330 360 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 5 documented codes

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Loss of system water pressure

Your boiler has lost the water pressure it needs to circulate heat, likely because there is a small leak somewhere in your radiator pipes or the boiler itself.

High DIY-safe £80-250

What to check first

  1. Locate the filling loop, which is a silver braided hose with a valve positioned underneath the boiler.
  2. Open the valve(s) to allow a small amount of cold water into the system until the pressure gauge needle sits back in the green zone, usually between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly to stop the flow and ensure the pressure remains steady.

Parts commonly replaced

  • Pressure relief valve
  • Expansion vessel
  • Filling loop
Full explanation for Loss of system water pressure
Neon I3

This light simply indicates that there is power reaching the boiler and it is switched on.

Low DIY-safe

What to check first

  1. Check that the boiler power switch is on
  2. Ensure no other fault lights are flashing
  3. Monitor the boiler for normal operation
Full explanation for Neon I3
Neon l3

Your boiler is receiving power and is currently standing by, meaning it is ready to operate correctly.

Low DIY-safe

What to check first

  1. Verify the boiler's thermostat or external heating controller is set to demand heat
  2. Check that the radiator or hot water setting is turned on
  3. Ensure radiators are not turned down at the thermostatic valve
Full explanation for Neon l3
Neon SG1

Your boiler is currently trying to light the flame, which is a normal part of its startup sequence.

Low DIY-safe

What to check first

  1. Observe the light to see if it stops flashing and stays on (solid) or turns off once the boiler is running
  2. Check if the gas supply is turned on if the boiler fails to light after several attempts
  3. Press the reset button if the light continues to flash without the boiler firing up

Parts commonly replaced

  • Ignition Electrode
  • Detection Lead
  • Gas Control Valve
Full explanation for Neon SG1
Overheat thermostat

Your boiler has become too hot and has automatically turned itself off to prevent damage or dangerous conditions.

High Engineer only £120-250

Parts commonly replaced

  • Overheat thermostat
  • Pump
  • Diverter valve
  • Heat exchanger
Full explanation for Overheat thermostat