Gas burner lights but goes out when the knob is released.

Safety first: If the burner repeatedly goes out, avoid holding the knob down for long periods. Ensure the area is well ventilated.

Steps to check:

• Clean and align burner: Remove and clean the burner head and cap. Make sure the flame ports near the thermocouple are clear and the cap is correctly seated.
• Observe flame: Light the burner and hold the knob in. The flame should directly contact the thermocouple tip. If not, adjust the cap position.
• Hold time: Keep the knob pressed for 5–10 seconds after ignition to allow the thermocouple to heat. If the flame still goes out immediately when released, the thermocouple or valve magnet may be faulty.
• Thermocouple replacement: Replacing the thermocouple involves accessing the underside of the hob and disconnecting it from the gas valve. This should be done by a Gas Safe registered engineer.