Glow-worm Space Saver Fault codes & diagnostics

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

Regular Natural Gas Discontinued

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8 High
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The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 8 documented codes

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Neon 1 NOT lit

Your boiler appears to have no power reaching it, which is likely caused by an external electrical issue or a blown fuse inside the unit.

High DIY-safe £80-180

What to check first

  1. Check if your home's main fuse board (consumer unit) has tripped and flip the switch back if necessary.
  2. Locate the fused spur switch near the boiler (usually a wall switch with a red light) and ensure it is turned on.
  3. Check if other appliances in the house are working to rule out a general power cut.

Parts commonly replaced

  • PCB Fuse
  • Printed Circuit Board (PCB)
  • External Fused Spur

Related codes

Full explanation for Neon 1 NOT lit
Neon 2 NOT lit

Your boiler has switched itself off because it has reached an unsafe temperature or a safety sensor has detected a fault.

High DIY-safe £90-180

What to check first

  1. Locate the overheat reset button under the boiler control panel
  2. Press the button firmly to reset the trip
  3. Ensure all radiator valves are open to allow water to circulate

Parts commonly replaced

  • Overheat Thermostat
  • Control Thermostat
  • Circulation Pump

Related codes

Full explanation for Neon 2 NOT lit
Neon 3 NOT lit

Your boiler has stopped working because it cannot confirm that the internal fan is safely clearing waste gases from the system.

High Engineer only £120-300

Parts commonly replaced

  • Fan motor
  • Air Pressure Switch
  • Venturi tube

Related codes

Full explanation for Neon 3 NOT lit
Neon 4 NOT lit

Your boiler has failed to light the pilot flame or cannot verify that the burner is safely lit, resulting in no heating or hot water.

High Engineer only £120-280

Parts commonly replaced

  • Thermocouple
  • Pilot Injector
  • Gas Valve
  • Ignition Lead
Full explanation for Neon 4 NOT lit
neon1

Your boiler is not receiving the correct electrical power, meaning it cannot start the ignition process to provide heating or hot water.

High DIY-safe £90-180

What to check first

  1. Check your home's main fuse box or consumer unit to see if a circuit breaker has tripped.
  2. Ensure the boiler's isolation switch (usually a fused spur near the boiler) is turned on.
  3. Check if other electrical appliances in the house are working to rule out a local power cut.

Parts commonly replaced

  • External fuse
  • Printed Circuit Board (PCB)
  • Wiring harness

Related codes

Full explanation for neon1
neon2

Your boiler has likely stopped heating because it has reached an unusually high internal temperature and has shut down as a safety precaution.

High DIY-safe £90-180

What to check first

  1. Wait for the boiler to cool down completely.
  2. Locate the overheat reset button on the control panel or underside of the unit.
  3. Press the reset button firmly to see if the boiler restarts.

Parts commonly replaced

  • Overheat Thermostat
  • Pcb
  • Pump

Related codes

Full explanation for neon2
neon3

Your boiler has detected an internal electrical communication error, meaning it cannot safely confirm the fan is working to clear waste gases.

High Engineer only £180-350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Air Pressure Switch
  • Yellow Wiring Harness

Related codes

Full explanation for neon3
neon4

Your boiler is unable to light the pilot flame, which means it cannot fire up to provide heating or hot water.

High Engineer only £180-350

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Pilot Gas Valve Solenoid
  • Wiring Harness

Related codes

Full explanation for neon4