Ariston boiler models and common faults.

Ariston ranges we work on

Current ranges: Alteas ONE Net, Genus ONE Net, Clas ONE Net, Clas ONE R, Clas System ONE, E-Combi ONE, E-System ONE.

Older ranges we still see: Genus HE, Clas HE, E-System evo.

Model names you may find on the label

Alteas ONE Net 30 and 35, Genus ONE Net, Clas ONE 24, 30 and 38, Clas ONE R, Clas System ONE, E-Combi ONE 24 and 30, E-Combi 24, 30 and 38, E-System ONE, Genus HE 24 System, E-System evo 24 and 30, Clas HE System evo 18, 24 and 30, Clas HE 24 Regular.

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 Ariston boilers

Ariston notes from trade guides

• Failure to ignite. Faulty ignition leads, an airlock, a blocked burner, a spark generator fault or low gas supply can all stop ignition.
• No pilot light. On models with a pilot, a flue draught, faulty thermocouple, blocked gas valve or flue blockage can put it out.
• Circuit board, fan and air pressure switch faults. Loose wiring, water damage, a fan not receiving power or a faulty air pressure switch can each lock the boiler out.

Faults common to most gas boilers, Ariston 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 Ariston 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 Ariston 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.