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There are several types of car solenoids used to perform a variety of functions, from starting the engine to shifting the transmission. Many automobile starters use different types of car solenoids depending on whether or not the vehicle is equipped with a standard or an automatic transmission. There are different car solenoids used to activate a four-wheel drive system, fuel-injection system and even to lock or unlock the doors and trunks on some vehicles.
A solenoid is an electronic device that operates either a push or pull operation, and some car solenoids can both push and pull. The most common use of car solenoids is to start the engine of the vehicle. The starter solenoid can be either attached to the engine's starter or divorced from the starter. In a divorced solenoid application, the solenoid is commonly mounted on the vehicle's fender well or on the firewall. Some car solenoids are used to direct transmission fluid to a certain sector within the transmission to control the gear shifts.
Automatic transmissions commonly use a solenoid to direct the transmission fluid while under computer control. The vehicle's computer will send an electrical charge to a solenoid inside of the transmission. The signal activates the distribution and flow of transmission fluid that will allow the vehicle to change gears.
Other solenoids control the lock-up action of the vehicle's torque convertor to aid in improving fuel mileage by eliminating torque convertor slip while driving. In four-wheel drive applications, a solenoid typically controls the locking mechanism in a vehicle's front axle or transfer case. The solenoid eliminates the need for the operator to shift the transfer case into a specific gear by allowing the operator to turn or push a switch that electronically locks the transfer case when needed.
Some car solenoids are used to open doors, trunk lids and rear hatches remotely. The solenoid used in this application is commonly a push or pull type solenoid and is attached to the locking mechanism by a rod or cable. Another type of solenoid is found in the fuel injection system of a vehicle. The fuel injectors are electrical devices that pulse back and forth releasing a pre-measured shot of fuel on each cycle. Many vehicles also use a type of solenoid to control the flow of heated engine coolant to and from the vehicle's heater, and this flow of heated coolant provides warmth to the vehicle's passenger compartment.