Solenoids

Solenoid operation is as follows:

• A large amount of current, typically in amps, is allowed in the coil of wire.

• As the Danish physicist Hans Christian Oersted discovered, the current in the coil of wire produces a strong magnetic field around the wire.

• The iron center inside of the core is pulled towards the magnetic field.

• The iron center inside of the core is attached to a lever, valve, plunger, etc.

• The movement of the iron center inside the core performs mechanical work by moving the lever, valve, plunger, etc.

REMEMBER - Solenoids use large amounts of current to perform mechanical work.

Examples of commonly used solenoids on vehicles include:

• Starter Solenoid - The spring loaded moveable core of a starter solenoid pulls on a lever which engages the starter drive to rotate the flywheel of an engine.

• Electronic Fuel Injectors - The moveable core of an electronic fuel injector pulls open a spring loaded valve which allows fuel to be delivered into the intake port of a cylinder head.

• Evaporative Purge Solenoid - The moveable core of an evaporative purge solenoid opens a spring loaded valve to allow fuel vapors from the vapor canister to be drawn onto the engine to be burned.

• Fuel Tank Vent Solenoid - The moveable core of a fuel tank vent solenoid opens a spring loaded valve to allow fresh air to be drawn into the fuel tank while the evaporative canister is being purged of vapors.  The fuel tank vent solenoid is also used during evaporative system leak checks.

• Transmission Shift Solenoids - The moveable core of a transmission shift solenoid pulls on a spring loaded plunger which holds a check ball in place.  The movement of the check ball routes transmission fluid to different passages inside the transmission to complete an upshift or downshift.

• Transmission Pressure Control (PC) Solenoids - The moveable core of a transmission pressure control solenoid is pulsed back and forth many times per second to control the hydraulic pressure inside an automatic transmission.

• Transmission Torque Converter (TCC) Solenoid - The moveable core of a transmission torque converter control solenoid is pulsed back and forth many times per second to control the apply and release of the torque converter clutch.