Wednesday, January 30, 2008

Under hood Maintenance: Windshield Washers and Wipers

Wiper Blades

The windshield wiper system is another area that requires periodic service. The wiper blades are inspected and replaced when they are worn out. The windshield washer fluid reservoir is inspected and refilled when it is low. The technician who performs these services should have a basic understanding of how the system works.

An electric wiper motor, located under the cowl panel, provides the power for the system. When the wiper switch is turned on, the motor begins to move a linkage system back and forth. This motion is transferred to a set of wiper arms on the outside of the windshield. Wiper blades attached to the arms move back and forth across the windshield.

When the windshield needs washing, the driver can turn the wiper switch to activate the washer system. The washer system consists of a reservoir, pump, hose, and washer nozzle. The reservoir contains windshield washer fluid. An electric pump in the reservoir pumps cleaning fluid out of the reservoir through a hose to the washer nozzle. The nozzle is located below the windshield and directs a spray on the windshield. When the washer is activated, the wipers are also activated so the wiper blades move the fluid across the windshield to clean it.

The windshield washer fluid reservoir is a plastic bottle. The reservoir is located under the hood in the engine compartment. The level of washing fluid can be observed through the container. Washer fluid is available in containers from automotive parts stores. Always check the owner's manual for the recommended type of fluid.

The wiper arm is attached to the linkage from the wiper motor. The wiper blade assembly is the part that contacts the windshield. It has a metal support that holds a rubber wiper blade. The support holds the rubber blade in the proper position against the windshield.

Inspect and Refill Windshield Wiper Fluid

The windshield washer system must have enough windshield washer fluid to properly clean the windshield. Anytime you service the windshield wipers or are under the hood, inspect and refill any lost windshield wiper fluid.

Windshield washer fluid is available in automotive parts stores. The fluid is often colored blue so that it is easy to see in the washer system reservoir.

Open the hood and locate the washer reservoir Typically, the reservoir is transparent so the fluid can be seen through the reservoir. Inspect the fluid level. Some reservoirs have a "full" line, but most are filled all the way to the top. If the level is low, remove the cap on top. Place a clean funnel in the cap opening and pour in the washer fluid until it reaches the correct level.

WARNING: You will need to add windshield washer antifreeze to prevent the washer fluid from freezing in cold weather conditions.

WARNING: Never use dirty fluid or a dirty funnel in a washer system. Dirt in the system can clog the tiny jets that spray the fluid on the windshield.

Remove and Replace a Windshield Wiper Blade

The rubber wiper part of a windshield wiper blade deteriorates from contact with sun and smog. It wears from contact with the windshield. Worn windshield wiper blades will not properly wipe the windshield. They could create a safety hazard for a driver in bad weather. A wiper blade can get so worn that the rubber part separates from the metal part. The metal part could then scratch the windshield when the wipers are turned on. Consequently, the wipers should be inspected regularly and replaced as necessary.

Worn wiper blades may be replaced in two ways. You can buy an entire wiper blade assembly or just a rubber insert . The insert is less expensive and a good choice for a newer car. The wiper assembly is a good choice on an older car in which the metal wiper parts are corroded or damaged.

To replace either the blade assembly or just an insert, remove the blade assembly from the wiper arm. There are many types of retaining systems used between the arm and blade. The most common is the release lever. You release the arm from the blade by lifting up on the tiny release lever.

Often the insert is held with spring clips called bridge claws or lock tabs. A button may have to be pushed to disengage some types. You will have to squeeze or pinch other parts to release the lock tabs.

Be careful not to lose the small parts during disassembly and reassembly. Always compare the replacement parts with the new ones. When you have installed the new blade assemblies or inserts, test the system. First clean all dirt or dust from the windshield. Pour water on the glass and turn on the wipers. Check to see that they do a good job wiping the water.

WARNING: Never operate wipers on a dry or dirty windshield. The blades could rub the dirt over the windshield and cause scratches.

SERVICE TIP: Never disassemble both wiper assemblies at the same time. Do one at a time and use the assembled unit as a guide for correct assembly.


How often should I replace my wiper blades?

Wiper blades are one of the most neglected components on vehicles today. Many blades are cracked, split, torn, brittle, worn or otherwise in obvious need of replacement. Others may look okay, but do a lousy job of wiping when put to the test.
Ninety percent of all driving decisions are based on a clear unobstructed view of the road, which means good visibility is absolutely essential -- especially during wet weather when vision may be obscured by water, road splash, sleet or snow on the windshield. But good visibility requires wipers that are in good condition. If the wipers are chattering, streaking or otherwise failing to wipe cleanly and consistently, you need new blades -- NOW!

Most experts say wiper blades should be replaced every six to twelve months for optimum performance and driving visibility. That's because wiper blades don't last forever. Natural rubber deteriorates over time. Halogen-hardened rubber as well as synthetic rubber provides longer life. But eventually all blade materials fall victim to environmental factors. Exposure to sunlight and ozone causes the rubber to age, even if the wipers aren't used much.

As a set of blades age, they lose much of their flip-over flexibility and they're less able to wipe cleanly. They may develop a permanent set (called "parked" rubber) or curvature which prevents full contact with the windshield. This tends to be more of a problem on vehicles that are parked outside in the hot sun all day. The sun bakes and hardens the rubber. Then when the wipers are needed, they streak and chatter because they've taken a set and won't follow the curvature of the windshield. It can be very annoying as well as dangerous.

Cold weather can affect blade life, too. Freezing temperatures makes rubber hard and brittle, which increases the tendency to crack and split. The holders can also become clogged with ice and snow, preventing the holder from distributing spring tension evenly over the blade. The blade "freezes up" and leaves streaks as it skips across the glass.

Heavy use can be hard on wiper blades, too, because dust, abrasives, road grime and even bug juice wear away the edge that the blades need to wipe cleanly. As the blade loses its edge (which is precision cut square to maximize the squeegee effect), water gets under the blade and remains on the glass. The result is reduced visibility and poor wiping action.

Any blade that's chattering, streaking or doing a lousy job of wiping, therefore, is a blade that's overdue for replacement. The same goes for any blade that is cracked, torn, nicked or otherwise damaged.


A simple check is to try your windshield washers. If the blades are not in good condition, you'll see why when they attempt to wipe the washer solvent off the glass. Streaking, chattering or any other problems will be clearly obvious.

This test also gives you the opportunity to check your windshield washer system. Do both squirters work? If not, a nozzle may be plugged with dirt or a hose may be kinked or loose. Does the spray hit the windshield where it is supposed to? If not, the nozzles need adjusting. Does the washer pump deliver an adequate stream of solvent? If not, the vehicle may have a weak washer pump, or a clogged, kinked or loose hose. Most washer reservoirs have a screen to filter out debris that could clog or damage the pump. If this screen itself is buried under debris, it can choke off the flow of solvent to the washers.

After you've checked the windshield wipers, check the rear wiper too if your vehicle has a rear wiper system. Many sport utility vehicles, vans, minivans, station wagons, hatchbacks and fastbacks do. After all, it's just as important to see what's behind you when backing up in the rain as it is to see what's ahead. You can use the same test (try the rear windshield washer, if so equipped), or simply spray some water onto the glass with a squeeze bottle and see how the wiper performs.


How well the wiper blades perform also depends on the condition of the wiper arms and holders. A blade's wiping ability is affected by the amount of spring tension on the wiper arm, the number of pressure points or claws that hold the blade, and the design of the blade itself. If the springs in the arms are weak (which is more apt to be a problem in older vehicles), the wipers may not be pressed against the glass firmly enough to wipe cleanly. Replacing the blades won't make any difference because the problem is weak arms not bad blades.

If the blades can be pulled away from the glass with little resistance, it's time for new arms. Most vehicle manufacturers publish tension specs for their arms. If the arm doesn't meet the spec, it needs to be replaced.

Remember to check the tension on the rear wiper arm, too, because rear wiper arms are often damaged by drive-through car wash rollers.

Wind lift is another factor that can interfere with good wiping action at highway speeds. Many windshields are steeply sloped to improve aerodynamics. But steeply raked windshields with a lot of glass area direct more wind against the wipers. This can lift the blades away from the glass at high speed unless the wiper system and blades are designed to counter the aerodynamic forces. Some blades have specially designed vents and airfoils to minimize lift and/or generate downforce to keep the blades in constant contact with the glass as speed increases. If your original equipment blade holders need to be replaced, be sure the replacements have the same anti-wind lift design.

Another factor to keep in mind is the design of the blade holder. A blade holder needs to distribute the tension of the wiper arm evenly over the blade while also allowing the blade to flex as it follows the changing curvature of the glass. The better quality replacement blade holders typically have six to eight claws to spread the pressure of the wiper arm over the blade. More claws also increases flexibility so the blades don't lose contact at the sides of the glass.


You can usually replace wiper blades yourself, and can replace just the blade with a refill or the entire blade assembly. Refills will save you money. If you're installing a blade assembly, most come with some type of adapter to fit the arms on your vehicle. The old blades pull or push off the arm by pressing a release button or pin on the wiper holder.

If you are replacing the blade only with a refill, the old blade can be removed by squeezing the locking tags in at the end of the blade so it will slip out of the holder. Make sure the replacement blade is the same length and claw width as the original. A blade that is too long may create interference problems, while one that is too short may not fit the holder.

For cold weather driving, you might consider installing a set of "winter blades" on your vehicle. These have an enclosed holder that prevents ice and snow from building up and interfering with the wiper's ability to do its job.

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