Auxiliary Air Valve (Idle Speed): Description and Operation

Thermal - Wax Valve:

The thermo - wax valve, located on the throttle chamber, is used to provide cold engine fast idle. When the engine is cool the special wax in the unit is compacted and as the engine coolant warms the wax, it expands. On the end of the unit is a lever that contacts a group of linkages, through a cam. During cold engine conditions, the lever pushes upon the linkages, opening the throttle valve. As the engine warms the cam assembly rotates, allowing the throttle valve to close, lowering the engine speed.