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What are wipers/what do they do?

Wipers are a standard safety feature in cars and can be positioned on both the front and rear windscreen of the car. Most cars have two wipers on the front windscreen, one on the driver side and one on the passenger side. Rear windscreens tend to have just one long wiper that sweeps across the whole of the windscreen. The driver needs to look through the front windscreen to see the road ahead, and through the back windscreen to see the traffic behind, so it is imperative that the windscreens are in perfect, clean condition.

The wiper consists of a wiper arm and a wiper blade. The wiper blade is made from rubber and as the arm is powered to move across the windscreen, the rubber blade moves the water and debris from the surface of the windscreen, clearing the screen to enable a clear vision of sight for the driver.

Getting into the details of the wipers

A wiper linkage is the mechanism responsible for movement of the wiper arms. Driven by the wiper motor, the linkage is moved back and forth by cams. The motor and linkage mechanism is located beneath the bonnet, generally concealed by a plastic scuttle panel. The wiper arms are normally bolted or attached to the linkage on studs or splines that protrude through the scuttle panel. Arms can often be difficult to remove by hand as the splines are mostly tapered. Special universal tools can be used to lever off the arms.

The driver can decide at what speed the wipers move, usually from a choice of three speeds, depending on the weather conditions. The driver can operate the wipers by selecting the desired speed on the wiper switch stalk, which is usually mounted on the steering column. This activates the wiper motor switch, which operates with a wiper motor relay.

Many car windscreens are also fitted with a windscreen washer. Powered by a windscreen washer motor, it pumps out a spray, which works with the wipers to clean the windscreen.

What if something goes wrong with the wipers?

An old and worn out wiper blade will be ineffective and need to be replaced as soon as possible. Signs that you need to buy new wiper blades include streaks of dirt left on the windscreen; inability to remove sufficient water from the windscreen in heavy rain; a screeching sound from the wipers when in operation; and wipers being lifted off the windscreen by the wind when driving along.  Broken or worn out wiper arms will not function properly and will also need to be replaced. If the motor and linkage mechanism wear out, the wipers will not work and replacement parts should be fitted. If the wipers are not working or only working intermittently, there could be a problem with the wiper switch stalk. If wiper problems strike, it's a good idea to consult your mechanic to identify which specific part needs replacing.

A car's windscreen washer and wiper systems should ensure the windscreen is clean and clear enough for the driver to be able to drive safely in all weather conditions.