Windshield wipers play a critical role in your car, especially during rain or when driving on a dusty road.
But since this component rarely encounters problems, they tend to be neglected during regular maintenance.
However, you should know that a malfunctioning windshield wiper can cause accidents.
It happens when it can’t wipe off the rain or dust, making them interfere with your eyesight.
Besides, if the windshield wipers turn on by themselves, they will drain the battery, making it not last long.
Luckily, you can find below the things that make them come on by themselves and how you can solve them.
9 Reasons Why Windshield Wipers May Turn On By Themselves
1. Faulty Wiring
The windshield system uses a voltage supplied by the car’s battery. Therefore, its wiring should not be faulty for it to work usually.
But sometimes, due to maintenance by a less skilled mechanic or accidents. For instance, they can allow voltage to pass through even when the windshield system is turned off.
When this happens, the windshield wipers will turn on by themselves.
So, it would be best if you have the windshield wiring checked and fixed by a professional to resolve the problem.
Do the windshield wipers turn on by themselves only during the rainy season or early mornings? If so, it is due to moisture.
Moisture can get into the relay compartment and cause short circuits that turn the windshield wipers on.
Luckily, it is easy to fix the issue since you will have to open the relay box and wipe it using a piece of cloth.
But to avoid reencountering the problem, try to find out how the moisture got into the box and have it sealed properly.
3. Faulty Park Switch
The park switch is a component in the windshield motor that regulates voltage flow to the wipers. If it gets faulty, the current will flow continuously or stop flowing.
If the current flows continuously to the wipers, the windshield wipers will turn on by themselves. It can happen even when the car is off.
But how does this happen? Well, the wipers will draw voltage from the battery.
It is not only irritating but will also result in low battery voltage. Therefore, you should fix or replace the motor to eliminate the problem.
Remember that fixing or replacing it may not be easy since navigating through the steering column. Therefore, it will be best to let a professional handle it for you.
4. Faulty Stalk
The windshield wipers are controlled by a stalk next to the steering wheel. If you want to turn on the wipers, press the stalk once.
But this stalk can also break inside and thus complete the circuit. When this happens, the windshield wipers will turn on by themselves.
Pressing or pulling the stalk will not affect the windshield wipers. Like the park switch, repairing the stalk might not be easy.
It is because you will have to remove the screws and plastic covering. You will also have to disengage some parts of the steering column.
Fortunately, many videos on Youtube will teach you how to do so.
5. Dried Grease
There is a dielectric grease on the relays whose purpose is to prevent electric arcing.
But due to overheating, this grease can dry up, letting the voltage flow through even when the park switch is off.
In such a case, the windshield wipers will turn on by themselves. The good news is that it is pretty easy to spot dried grease.
You open the relay compartment and check if it is still there. If it has dried up, you must smear the correct amount and the proper grease on the relay.
You can use your car’s manual to guide you on how to do it.
6. Bad Relay
If you still can’t figure out the problem, it might be time to examine the entire relay. The relay is an internal switch mechanism in the windshield system.
It is a small box in the hood of your vehicle. It tells the wipers what to do; hence, they might continue moving if they go bad.
For instance, the windshield wipers will turn on by themselves if the last instruction they receive from the relay is to move.
Unfortunately, repairing a bad relay is not easy since it requires a deep understanding of how an electrical system works.
But if you have the time and a passion for electrical systems, you can fix it yourself by following online videos.
7. Malfunctioned Body Control Module (BCM)
If you are using a modern vehicle, the windshield wipers are controlled by a BCM.
But since the BCM is a computer, it can encounter bugs that make it behave abnormally. For instance, it can activate the windshield wipers even when the car is not raining.
Thankfully, this is a temporary problem that you can solve by restarting the BCM.
To go about this, disconnect the car’s battery and wait for about 15 minutes before connecting it back.
It should fix the problem, not unless it was caused by something beyond a temporarily malfunctioned BCM.
8. Faulty Rain Sensor
If your car is modern, you probably have a rain sensor installed inside its windshield.
This sensor calculates the number of reflections when raining and sends signals to the BCM.
Therefore, if it malfunctions, it might send a false signal that will make the windshield wipers turn on by themselves.
In this situation, you will have to examine the rain sensor.
To diagnose if the rain sensor should be blamed, check if all other components are working correctly. If so, you have a faulty rain sensor that needs to be repaired or replaced.
Fortunately, if you are far away from a mechanic shop, you can disable the rain sensor via your car’s infotainment system.
It will shut off the automatic mechanism that uses this faulty sensor.
9. The Rubber Gasket Is In The Wrong Position
Windshield wipers can also turn on by themselves if the rubber gasket is in the wrong position.
The rubber gasket is a transparent component between the windshield and the sensor. Its purpose is to allow the rain sensor to detect the rain without getting exposed to water.
But due to accidents, it can be displaced from its position. It will allow all the infrared light to reach the sensors.
Consequently, the BCM will be activated to turn on the windshield wipers even when not driving.
So, it will be best to check the rubber gasket and reposition it correctly to solve the issue.
The windshield system can malfunction in all car models.
For instance, your car’s windshield wipers can turn on by themselves due to a problem with one of the windshield components.
These components include the BCM, the rain sensor, the park switch, the relay, and the stalk.
But it is also good to know that other things unrelated to these components can also affect the wipers, such as moisture and grease.
It would be best if you thus made an effort to diagnose and fix the real cause of this issue to make the windshield wipers usually work.
Kevin has been hanging around cars and automobile magazines since he knew what a car is. He grew up in his father’s 1995 Mercedes E320 Wagon and Volkwagon Phaeton W12 2004. He rides his first car, a manual 1979 Porche 911SC.
Currently, he owns an Acura Integra GS-R. During his childhood, he showed a keen interest in how things actually work and fix them. This passion transforms into his eternal love for cars and bestows him an ideal position in one of the leading automobile companies; whenever he finds time, he takes out his Acura and opts for the longest possible route to find hidden wholesome pleasure in a road trip.
Want to read some of the articles written by Kevin? Head to our blog section to find out all the articles written by Kevin.