The windshield wiper system is easily one of the most crucial systems on your vehicle. Don’t believe me? Just wait for the day your wipers suddenly stop working while you are driving in the rain or a heavy snowstorm. You’ll see what I mean.
Luckily, wiper systems are also one of the easiest systems to troubleshoot and repair. This article will help you learn everything you need to know to quickly find the faulty part. It will also teach you how to fix the problem yourself.
See also: 5 Best Winter Wiper Blades 2020
How Wipers Work
Most wiper systems work the same. Generally, when you turn on the main wiper control switch, the power coming from the battery passes through a fuse to make the wiper relay click. The relay then supplies power to the wiper motor, driving the wiper linkage, and ultimately making the wipers move. Pretty simple right? But, if any of these parts happen to come into failure at some point, it will definitely cause the wiper to stop working.
Main Causes of Wiper Failure
Loose Pivot Bolts
Before trying to diagnose anything, always try to move the wipers with your bare hands first. If you can easily make the wipers move, check that the pivot bolts are tightened correctly. Lots of mechanics every year try to solve wiper problems by testing the electrical side first. They are quick to find out that the pivot bolts weren’t even tight enough and that the pivots were turning inside the wiper arms.
Worth mentioning, some newer car models may be equipped with electromagnetic wiper systems, allowing the wipers to move freely whenever the key is not in the ON position. Remember to always test your wipers while keeping the key ON and the parking brake applied.
Wiper Fuses
Fuses are almost always the first thing to check when troubleshooting any electrical problems. They are the main cause of over 60% of all electrical faults. It’s simply quicker to just take a look and test them for continuity before starting to remove trims and all. Use a test light and test for power coming in and out of the wiper fuses. If a blown fuse is found, replace it and activate the wipers to see if everything is back to normal.
If it works, you may have found your problem but you may not be out of the woods yet. Fuses just don’t blow out for no reason. The main cause of blown wiper fuses is turning on the wipers when they are covered in ice.
If a fuse was blown and you are absolutely sure they weren’t started while being frozen, be sure that some other intermittent problem may be lurking in the shadows. Fuses also tend to blow out when the wiper linkage is about to seize or when the wiper motor is about to die.
If the new fuse blows out again, you may have a short to ground condition. Any skinned area of any positive wire touching the vehicle’s body will cause a short to ground. This will make the fuse blow out instantly. But, finding a short to ground is probably the hardest task to perform on this list. So, we strongly suggest you test the linkage and motor first. That way you don’t end up removing all the trims in your car for nothing.
So it’s not working at all, the blown fuse was probably a consequence rather than the cause of the problem. The most probable reason is that the motor or the linkage might have seized.
Wiper Relay
Incidentally, if the wiper relay sticks or stops doing its job for some reason, the wiper system will also fail. The fastest way to test a relay is to simply put your finger on it while somebody else turns the wiper switch to ON. If you are working alone like I am, tie a long string to the wiper switch so you can activate it while standing in front of the car. Keep your thumb on the relay.
If it’s in good working condition, you should hear and feel a short *click* coming from the inside. So, if that’s the case, the relay is ok. You can safely assume the control switch is also working. If it wasn’t, no power would come to the relay and it wouldn’t do a thing.
If you think the relay might be your problem, try removing it and test for power and ground coming from the connector using a test light. You should have two grounds. One positive and one switched positive. Your test light will only light up when the wiper switch is activated.
If something is wrong with the 2 grounds or the positive, look for a short or open in the wires. So, if the switched power is the problem, the cause has probably something to do with the control switch.
If everything seems fine with the powers and grounds, and the relay is still not clicking, try replacing it with another relay in the fuse box. Test it again. If your wipers are back to normal, you know your relay is burnt and it needs to be replaced.
Seized Wiper Linkage
The wiper linkage is a set of metal bars all linked together by pivot points, transforming the unidirectional motion of the wiper motor into a bidirectional movement. It’s basically what makes the wipers go back and forth instead of just moving in one direction. All the pivot points are filled with grease from the assembly line. But, after a while, water and dirt can cause rust to build up. It ultimately prevents the pivots from being able to move freely.
When something like this happens, you should be able to see it coming. Your wipers should visibly start to move slower and slower for a while until they simply stop moving altogether or blow the main wiper fuse.
To check if linkage seizure is your problem, remove the plastic trim below the windshield to uncover the wiper motor (you’ll probably have to remove the wipers to do that). Push the rod connected to the wiper motor’s pivot point to disconnect the linkage from the motor. When it’s done, the linkage should move freely, without any kind of restriction whatsoever. If it does, the problem is definitely somewhere else.
If it doesn’t, you have found your problem. You’ll need to remove the seized linkage and replace it. Some people would argue that you can disassemble the whole thing. Then, clean it thoroughly, pack the pivots with new grease, and re-install everything. And they would be right.
But, I don’t suggest you do that unless you own a Land Rover or some other expensive exotic car. For such vehicles, a replacement linkage is really hard to find or super expensive. The small retaining rings holding everything in place must be replaced every time they are removed. They are quite hard to find in aftermarket part stores.
Wiper linkage assemblies for common domestic and Japanese cars are usually not that expensive so it’s simply not worth the hassle. Just buy a new one if you can. If you can’t, you can always try to rebuild your linkage. But, be warned, it’s not as simple as it looks. DIY rebuilt linkage doesn’t always last as long as new ones.
Seized or Burnt Wiper Motor
Another frequent cause of wiper malfunction is a defective motor. The wiper motor can seize for the same reasons as the wiper linkage. But because the motor is made out of multiple electrical components, it can also be subject to internal shorts and open circuit problems.
To test for a faulty wiper motor, all you need is a test light or a basic voltmeter. Simply unplug the electrical connector at the motor and test for power and ground. Electrical motors are quite simple and if there are power and ground coming to the motor, it should turn. If it doesn’t, the motor is probably seized or burnt and you need to replace it.
If there is no power or ground coming to the motor, any other electrical component could be faulty. This is where the real troubleshooting starts.
Faulty Control Switch
The next thing to check if there’s no power to the motor is the wiper control switch. It’s also called a combo switch or multi-function switch depending on the manufacturer. The control switch’s main task is to close the wiper relay circuit. This makes the relay click and ultimately supplies the motor with power. If there’s a bad contact at or inside the switch, the relay won’t click and there won’t be any power supplied to the motor.
The fastest way to check your control switch is to locate the relay and see if it’s clicking when the switch is activated. Normally you should have tested that before but just to make sure. Once you have cornered the problem and you suspect a faulty control switch, the wise thing to do is to remove the trims around the steering wheel to access the control switch’s connector.
Power and ground should come at all times into the connector and power and ground should come out of the switch when it’s activated.
If no power or ground is coming to the connector (assuming that you have already tested and confirmed that the wiper fuses are ok), you should check for a short or open circuit in the wiring somewhere between the fuse and the switch.
On the other hand, if power and ground are coming in but one is not coming out of the switch, it’s definitely faulty and it needs to be replaced. If you have access to a shop manual including a control switch operation diagram, you can also locate which pins are controlling the low-speed wiper setting.
Try bypassing the switch by touching both control pins with a paper clip. The wiper should start working at low-speed letting you know that you have correctly pinpointed the problem.
Short to the ground or open circuit
If everything else fails and the fuses are good, the relay is working, all other components seem fine and there’s still no power or ground to the motor, it’s now time to take out your car’s shop manual and find the wiper system electrical diagram.
When every component of a system is in good working condition and there’s still no power to the unit, you can safely assume that something wrong is happening somewhere in the wiring. You now have to remove the trims and find all the connectors. This is where a shop manual with electrical diagrams can come in handy, especially if you don’t have a huge auto mechanic background.
Starting from the fuse, test for power and ground at every connector you can find until you are able to pinpoint where the problem is. Typically the problem should be located between the last good connector you have tested and the faulty one. The wire may be cut or slightly damaged and the uninsulated area comes into contact with the body. This causes a short to ground or open circuit condition.
Once you found where the wire is cut, remove at least 1 inch of wire around it and solder a new one. Theoretically, if you did everything right, things should be back to normal now.
Last words
Every situation where your wipers stop working is a bad situation. But being able to repair or replace the faulty part by yourself and save some money while you are at it will help to ease up the pain. Anybody with some basic auto mechanic knowledge can easily fix most wiper systems using a test light. It just takes a bit of patience, but it’s definitely one of the easiest systems to troubleshoot.
So next time you find you find yourself having wipers problems, put the fear aside, grab your tools, and fix it yourself. You’ll not only save money but you’ll also realize that keeping your car far away from the repair shop might be way easier than you think.
