Baxi 102005 Honeywell Thermocouple

The Baxi 102005 is a thermocouple supplied under the Honeywell Q309A2721 reference. It is a flame-sensing device built from two dissimilar metals which generate a small electrical charge when the tip is heated by a pilot or burner flame. That charge energises an electromagnet inside the gas valve, holding the valve open so gas can continue to flow while a flame is proven.

As a Baxi spare, it belongs to the manufacturer's range of gas appliance safety and ignition components and is classified as a thermocouple within the thermocouples spare part group.

• The pilot flame lights but goes out as soon as the control knob is released.
• The appliance repeatedly locks out or shuts down shortly after ignition.
• The pilot will not hold at all, even when the knob is held down for an extended period.
• Flame failure faults appear intermittently, with the appliance running normally on some attempts and dropping out on others.
• The thermocouple tip shows heavy sooting, corrosion or a damaged lead, and cleaning the tip does not restore reliable flame proving.

• This part is fitted to a gas appliance; installation must be carried out by a Gas Safe registered engineer.
• Confirm the appliance model and, where available, the GC number against the compatibility list, as thermocouples are not interchangeable between all models.
• Check the part number on the existing component or in the appliance's service documentation matches BAXI102005 before ordering.
• Inspect the pilot assembly and its seals at the same time, as a worn injector or disturbed seal may need attention alongside the thermocouple.