Glow-worm Space Saver Compleheat 30 40 50 Fault codes & diagnostics

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

Regular Natural Gas 8.8-14.7 kW 1988-1994 Discontinued
GC Numbers 41-315-3841-315-3941-315-40

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 Glow-worm Space Saver Compleheat 30 40 50 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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Neon 1 NOT lit

Your boiler has lost power or has insufficient water pressure to operate, meaning it cannot provide heating or hot water.

High DIY-safe £90-250

What to check first

  1. Check that the main power switch for the boiler is turned on
  2. Check your home's fuse box / consumer unit for any tripped switches
  3. If your system has a pressure gauge, check if it is below 1.0 bar and top it up using the filling loop

Parts commonly replaced

  • Main PCB
  • Low water pressure switch
  • Internal glass fuse
Full explanation for Neon 1 NOT lit
Neon 2 NOT lit

Your boiler has switched itself off to prevent overheating because the system is getting too hot or the water is not circulating properly.

High Engineer only £180-450

Parts commonly replaced

  • Circulating Pump
  • Overheat Thermostat
  • Control Thermostat

Related codes

Full explanation for Neon 2 NOT lit
Neon 3 NOT lit

Your boiler has detected that the internal safety fan isn't moving air properly, so it has shut down for safety.

High Engineer only £120-£350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Venturi tubes
Full explanation for Neon 3 NOT lit
Neon 4 NOT lit

Your boiler is failing to light the pilot flame or detect a steady flame, meaning it cannot start the heating process.

High Engineer only £120-280

Parts commonly replaced

  • Thermocouple
  • Pilot injector
  • Gas valve
  • Flame sensing electrode
Full explanation for Neon 4 NOT lit
Red neon on fascia illuminated

Your boiler has detected that the water pressure is too low to operate safely and has shut down to prevent damage.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop, which is usually a silver flexible hose with two small valves.
  2. Slowly open both valves to allow fresh water into the system.
  3. Watch the pressure gauge and close both valves tightly once it reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • External filling loop
  • Expansion vessel re-pressurisation
  • Pressure relief valve
Full explanation for Red neon on fascia illuminated