Auxiliary air valves are part of the cold start system.
The auxiliary air device has a connecting hose from the intake air side of the throttle plate, to its controlling passageway. A return hose then connects from the passageway to the plenum chamber.
The controlling passageway is covered or uncovered by a blocking plate or disc, which is acted on by a bimetallic strip. The strip is heated electrically by a heater coil. The heating current is turned on when the engine starts. The heating effect bends the strip, which turns the blocking plate. As it turns, it changes the cross-section of the controlling passageway, to control the additional air required.
In a cold engine, the passageway is at its maximum set opening. Then, as the engine warms up, it gradually closes.
