Wipers can be powered in different ways. Although most of today’s wipers are powered by an electric motor that goes through a series of mechanical components, which are normally two 4-bar linkages in series or parallel. Vehicles that have air operated brakes sometimes use air operated wipers as well. These are run by a small amount of air pressure from the brake system to a small air operated motor that is mounted just above the windscreen. These wipers are activated by opening a valve that allows pressurized air to enter the motor.
Most wiper blades now operate together with the windscreen washer, which is a pump that supplies the water and detergent from the tank to clean the windscreen through small nozzles that are mounted on the hood or the bonnet or even on some of the wipers themselves.
Some of the more modern vehicles have small windscreen wipers or washers on the headlights. You can also find most vehicles are now fitted with wiper blades on the rear window as well. Rear window wipers are typically found on hatchbacks, station wagons, sport utility vehicles and some sports cars. These were first used in the 1970s but SUVs did not use them until the 1980s.
In the early part of the 21st century, rain sensing windshield wipers appeared. An infrared light is beamed at a 45 degree angle into the windscreen. If the glass is wet, less light will make it back to the sensor and this will cause the wipers to turn on.