“Flame starts then stops” on a boiler does not identify one failed part by itself. Common paths include temporary program/control state, sensor or user-interface input, cable, connector or communication path; the exact model, any error code and measured values determine diagnosis.
Most likely causes
- temporary program/control state
- sensor or user-interface input
- cable, connector or communication path
- control-board/software feedback
Safe checks you can do
- Check only user-accessible items such as the socket, valves, door and external hoses.
- Note any displayed code and the stage of the cycle when the problem begins.
- Photograph the model/product label and do not dismantle the appliance.
If gas is smelled, do not use the boiler. Close the gas valve if safe, ventilate, avoid electrical switches or open flames and contact the relevant gas emergency service. Also stop use for major water leakage, smoke or repeated electrical faults.
What does a technician check?
- stored error history and live sensor values where supported
- power supply, wiring/connectors and related actuator measurements
- functional testing of the relevant mechanical/hydraulic/air circuit
What to send with a service request
Share the brand, exact model/product code, any error code, when the issue started, the operating stage and a short photo/video when useful.
Related error codes
Frequently asked questions
Is a reset enough when the boiler is flame starts then stops?＋
A reset may clear a temporary control state, but a recurring symptom needs diagnosis rather than repeated resets.
Does this symptom always require a new part?＋
No. Settings, blockages, external connections and operating conditions can produce similar symptoms without a failed part.