Glow-worm EnergySaver Fault codes & diagnostics

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

Regular Natural Gas Discontinued

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 EnergySaver faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 3 documented codes

Tap any card for details

APS neon lit

Your boiler has detected an issue with the airflow system, which is preventing the burner from lighting for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube
Full explanation for APS neon lit
High neon light

Your boiler's status light indicates it is running at its maximum heating power, but if the light remains off while the boiler is struggling, there may be an internal electrical communication fault.

Medium Engineer only £90-180

Parts commonly replaced

  • High/Low Switch
  • Wiring Loom
  • Control Thermostat

Related codes

Full explanation for High neon light
Low neon light

Your boiler is struggling to maintain a strong flame, which is why it keeps turning off or failing to heat up properly.

High Engineer only £120-350

Parts commonly replaced

  • Gas valve
  • Ignition electrode
  • PCB
  • Burner
Full explanation for Low neon light