Baxi boiler models and common faults.

Baxi ranges we work on

Current ranges: Baxi 100, Baxi 200, Baxi 400, Baxi 600, Baxi 800, EcoBlue (Advance, System, Heat), Duo-tec Combi, Platinum, MegaFlo System.

Older ranges we still see: Combi Instant 105 e, Combi 105 HE, Combi 80 e, Combi 133 HE Plus, Duo-tec 28 HE, Solo (PF, PFL and HE), Bermuda.

Model names you may find on the label

Combi Instant 105 e, Combi 105 HE, Combi 80 e, Combi 133 HE Plus, Duo-tec Combi 28 HE, Solo 2 PF 40, 50 and 60, Solo 3 PFL 40, 50, 60 and 80, Solo 15, 18 and 24 HE, Bermuda 401 and 552, Baxi 100 HE, Baxi 100 Combi, Baxi 400 Combi, Baxi 200 Heat, Baxi 400 Heat, EcoBlue Advance, System and Heat, MegaFlo System.

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 Baxi boilers

Baxi notes from trade guides

• Ignition and gas supply lockouts. Baxi codes separate gas valve faults, interrupted gas supply and flame failure, so the code helps narrow the area.
• Temperature sensor faults. Central heating and hot water NTC sensor faults are reported on Baxi combi models.
• Pressure, circulation and fan faults. Water pressure too high or low, circulation faults and fan or flue faults each have their own codes.
• Safety thermostat. An operated safety thermostat points to overheating that needs investigating, not just resetting.

Faults common to most gas boilers, Baxi 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 Baxi 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 Baxi 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.