How Windshield Wipers Work

Here's how the windshield wipers work to clean the front window on your car.

The windshield wipers move in a repetitive translation sweeping motion across the windshield. This motion comes from a motor, that rotates. Using a crank slider (push pull rod) in addition to a four bar linkage, the repetitive sweeping motion is achieved from the wiper motor.

The wiper motor assembly consists of a spiral gear that engages the drive gear. This prevents the wipers from being forced down by hand. This also provides torque multiplication and speed reduction.

On the back of the drive gear is 3 contacts with a break in it at the home position. When the break lines up, the position of the gear indicates The park position of the wipers, breaks the drive circuit, and thus the motor knows when to come to a stop.

The wiper switch contains all of the electronics for the intermittent function. The motor itself has a resistor for built in hi and low speed control.

A steel wiper blade consists of small linkages that attach the frame to the blade. This helps to distribute pressure across its surface and is called a whippletree mechanism.

Finally, the washer tank, consists of the level sensor and pump. The level sensor is a reed switch, simply a magnetic switch that turns on when the float drops below a certain level to turn on the warning light on the dash board. The pump is a tiny DC electric motor with a small impeller to provide fluid flow from the tank out to the nozzles.

Automatic rain sensing wipers use an infrared sensor on the inside of the top of the windshield to sense rain droplets through reflection. A computerized system then activates the windshield wipers accordingly to keep the windshield clear.

The wiper and washer system in this video was demonstrated in a 2001 Toyota Corolla.