Glow-worm boiler models and common faults.

Glow-worm ranges we work on

Current ranges: Energy, Ultimate3, Easicom3.

Older ranges we still see: Ultracom (cxi, hxi), Flexicom, Betacom, Compact 80e, Micron, Spacesaver, Fuelsaver, Economy Plus, Ultimate FF.

Model names you may find on the label

Energy combi, system and regular, Ultimate3, Easicom3, Ultracom 30cxi, Ultracom2 35 store, 24cxi, 30cxi and 38cxi, 15hxi and 18hxi, Flexicom 15hx, 18hx, 30cx and 18sx, Betacom 24c, 28a and 30c, Ultimate 30c, Ultimate FF 40, 50, 60 and 120, Compact 80e, Micron 40FF and 60FF, Spacesaver 38 and 45-60, Fuelsaver 35f and 40-50b, Economy Plus 40F and 40B.

This is a guide, not a complete list. The model name is usually on the front of the boiler or on its data label, and a clear photo of it helps us prepare. If your model is not listed, send it to us and we will confirm before you book. Range and model names were compiled from manufacturer and trade sources on 6 November 2026; names and availability change, and parts for older models cannot be guaranteed.

Faults we are asked about on Glow-worm boilers

Glow-worm notes from trade guides

• Flame detection faults. A damaged flame sensor, circuit board fault, blocked burner jet, gas valve issue or blocked flue or condensate pipe can stop flame detection.
• Circuit board replaced or not configured. A replacement board that is the wrong model or not configured will not run the boiler, and may reveal pump or fan faults.
• Pilot light on older models. Older Glow-worm boilers with a pilot light can lose it because of a faulty thermocouple.

Faults common to most gas boilers, Glow-worm included

• Low or dropping pressure. A leak, recently bled radiators or a faulty pressure relief valve are the usual causes. A sudden drop suggests a leak; a gradual drop may only need repressurising.
• Hot water but no heating, or heating but no hot water. On a combi, a stuck diverter valve is a frequent cause of lost hot water. Timer, thermostat and settings (for example after a power cut or clock change) are worth checking first.
• Lockout in cold weather. A frozen or blocked condensate pipe, especially an external one, shuts many condensing boilers down. Low pressure, ignition or flame detection, a fan fault or a circuit board fault can also cause a lockout.
• Kettling, whistling, gurgling or banging. Limescale or sludge on the heat exchanger causes kettling. Air in the system, low pressure or restricted flow cause the other noises.
• Radiators cold at the top or bottom. Cold at the top usually means trapped air; cold at the bottom usually means sludge.
• Water leaking from the boiler. Worn seals, a pressure relief valve discharging or corroded parts are typical. An engineer needs to open the boiler to diagnose it.
• Switching itself off. Low pressure, a thermostat problem, a pump that is not circulating, closed valves or air in the system can all make a boiler cut out.

Trade guides do not tie these faults to particular Glow-worm models, so treat the lists as a guide to what a symptom can mean, not a diagnosis. A displayed code is useful evidence, not a confirmed failed component: the engineer assesses the boiler and the connected heating system before recommending the next step. Fault information was compiled from manufacturer and trade guides (including Which?, Checkatrade, HomeServe, Heatable and Boiler Guide) on 6 November 2026.

Next steps for your Glow-worm boiler

The diagnostic visit is £92.50 for the first 45 minutes. It covers initial fault finding; it does not promise a completed repair or include replacement parts. Once the fault has been assessed, we give you a fixed price for the repair before any work goes ahead. A diagnostic visit is the most reliable way to get there. If you would like to try first without a visit, report the fault and we will message you to ask for photos and a short video of the boiler, its display and the model label. Where those are enough, we can give you a fixed price without a visit; otherwise the diagnostic visit comes first.