Honda GOLDWING GL1800, Service Manual

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TECHNICAL FEATURES
24-2
TECHNICAL FEATURES
IDLE AIR CONTROL (IAC) VALVE
SUMMARY
The IAC valve is the electro-magnetic variable valve that controls the idle speed of the engine by passing air around the
throttle valves when they are fully closed. It controls the fluctuation of the idle speed and adjusts it to the basic idle speed
by supplying air to the intake manifold according to the engine coolant temperature, engine load, and the condition of the
throttle valves. When the coolant temperature is low, the IAC valve functions as the fast idle valve, too.
STRUCTURAL PRINCIPLE
As the IAC valve shaft rotates, the IAC valve opens and closes the air passage to control the air flow volume.
A magnet is mounted at the end of the shaft, i.e., in the oval hole in the iron core. Because the magnet is set at the center
of the oval hole, the magnetic force from the N-pole and the S-pole attracts the iron core of the narrowest air gap part to
the magnet, bringing the magnet to the position shown. The iron core is wound with a coil. Therefore, it turns into an
electro-magnet when electric current flows through the coil.