What’s the function of a windscreen wiper motor?
This compact electric motor is responsible for powering the car's window wiper system to wipe your windscreen clean of grime, mud, dust, snow and rain. It is therefore critical for maintaining visibility, especially if you live somewhere with a wet or snowy climate. When you switch your wipers on, the control module sends a 12-V current to the car wiper motor. The motor generates torque by rotating a shaft containing gears. This torque is then transferred to the wiper linkages via a crank. Once actuated, the linkages move the wipers back and forth across the windscreen.
To produce the necessary force needed to move the blades across the glass at a rapid pace, the motor is used in combination with a worm gear reducer. The gear reducer is able to multiple the torque by up to 50 times without increasing the rotation speed of the motor. This ensures that the motion of the blades is controlled and prevents the parts from wearing too quickly.
Types of wiper motors
There is a wide variety of car windscreen wiper motors available on the market, varying in terms of voltage rating, the magnet or coil used and where they are installed.
Voltage rating
- 6V
Usually only found on older vehicles. Due to the lower voltage, more power is needed to generate the torque required.
- 12V
The most common type of motor found in cars today, powered by a 12V car battery. Provides a sufficient amount of power for most applications.
- 24V
These are considered to be more efficient than the standard 12V components as they can generate the same amount of torque using less current.
Make sure to check the voltage rating of the factory fitted wiper blade motor before purchasing a new one.
Location
- At the front
Devices used for the front windscreen wipers are typically located in the engine bay beneath the wiper cowl.
- At the rear
Rear wiper motors are installed at the rear window and normally operate the wiper blade directly instead of via a crank.
The two types cannot be used interchangeably because of the way they are constructed.
Magnet type
- Permanent magnet
The vast majority of modern vehicles feature this type of motor due to the fact that they are quiet and efficient. Permanent magnets are also relatively cheap to produce.
- Field-wound magnet
You can generally find devices that use field-wound magnets on classic vehicles manufactured before the 1970s or around that time. However, as technology has advanced, these electromagnets have become outdated.
To find the right aftermarket wiper blade motor for your car, you can search online for a particular model, e.g. “Renault Clio wiper motor”. For more specific results, you can search using the VIN or the device’s OE part number.
Common window wiper motor problems
- The wipers are too slow or won’t move
Sometimes the motor or wiper transmission can get clogged up, causing the arms to move slower than normal or stop moving altogether.
- The wipers won’t ‘park’ correctly
Wiper motors usually have what’s known as a park limit switch. When this switch goes bad, the wipers may stop in the wrong place, preventing them from cleaning the glass effectively.
- A noisy motor
If the motor is making metal clunking or grinding noises, it could be due to a loose nut or wiper arm. A worn motor may produce a low humming sound.
- Speed won’t change
If the wiper switch isn’t changing the speed of the wipers, the cause could be a defective motor or control module.
Windscreen wiper motor repair and maintenance
In some cases, it may be possible to repair the component by replacing specific parts, such as worn brushes or a blown fuse. To keep the motor in working condition for as long as possible, you should avoid using the wipers when they’re frozen or when the glass is dry or covered in snow and ice. Make sure to top up the car screenwash fluid when necessary.
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