Car basics · Easy · about 10 minutes

Replace Windshield Wiper Blades

Wiper blades are strips of rubber that clear rain and snow so you can see. Sun, weather, and use wear the rubber out, and then it streaks or skips. New blades usually click on in a few minutes.

When to teach it: Watch from about 7, help from about 9, do it alone from about 12.

You'll need

New wiper blades in the right size
A towel
A tape measure

Before you start

Turn the car off. Some cars need the wipers moved to a “service position” first; your owner's manual explains how.
Lay a towel on the windshield in case the wiper arm snaps back.

Step by step

Tick each step as you go if you like; ticks stay on this device.

Get the right sizeCheck your owner's manual or measure each old blade before you shop.
Protect the glassLay a folded towel on the windshield under the wiper arm.
Lift the armGently lift the wiper arm up and away from the windshield.
Release the old bladeFind the tab, button, or clip where the blade meets the arm. Press or lift it, then slide the blade down and off the hook.
Attach the new bladeSlide the new blade onto the hook until it clicks. Close any clip or latch.
Tug testPull gently on the blade to make sure it's firmly attached.
Lower it gentlySet the arm back down slowly. Don't let it snap onto the glass; that can crack or chip the windshield.
Repeat and testReplace the other blade the same way. If you used the service position, turn the car on to bring the wipers back. Spray washer fluid to test them instead of running them on dry glass.

Physics

How it works: Why old wipers streak

A wiper works like a squeegee. Its rubber edge presses against the glass and pushes water off as it slides. The friction between rubber and glass depends on how hard they press together and on the two surfaces.

New rubber has a sharp, square edge that bends to fit the curve of the windshield. Over time, the sun's ultraviolet rays, ozone, very hot and cold weather, and grit wear the rubber down. The edge gets rounded, and the rubber dries out, hardens, and cracks.

A rounded or cracked edge can't press evenly on the glass, so water slips past and leaves streaks. Also, the grip needed to start something sliding is usually a bit bigger than the grip while it slides. A stiff blade that isn't gliding smoothly may stick and then jump, which you see as skipping or hear as chattering.

friction force = μ × N (μ depends on the two surfaces; N is how hard they press together)

Try it: Wet a bathroom mirror and pull a clean rubber spatula across it. Then press harder on one end so the edge doesn't touch evenly. Where the edge lifts, a stripe of water stays behind, just like a worn wiper leaves a streak.

Keep learning: Science

Teaching it to your kids

Let your child measure the old blades and write down the sizes.
Have them hold the towel and lift the arm while you watch.
Run a finger along an old blade and a new one to feel the difference in the edge.
Talk about why seeing clearly in rain and snow matters for safe driving.

Tips

Check your blades about every six months. Many mechanics and blade makers suggest replacing them every six months to a year.
Wipe the rubber edge with a damp paper towel to remove dirt and oil.
Clear ice with a scraper or the defroster, not the wipers.
Keep gasoline, paint thinner, and other solvents away from the blades.

Common mistakes

Mistake	Instead
Letting the bare wiper arm snap onto the windshield	Keep a towel on the glass and lower the arm gently.
Buying the wrong size	Check the manual or measure each old blade before you shop.
Running wipers on dry or icy glass	Spray washer fluid first, and clear ice with a scraper or the defroster.
Not clicking the blade all the way in	Tug gently to make sure it's locked before you lower the arm.

Safe habits

Lower the wiper arm gently. If it snaps back, it can crack or chip the glass.
Replace blades once they streak or skip. Worn blades make it harder to see in rain, snow, and dust.

When to call a pro

If new blades still skip or don't touch the glass evenly, the wiper frame or arm may be bent. Have a shop check it.

Sources

Free how-to guides for families, with nothing to earn, pass or send in. They follow U.S. rules and sources; your owner's manual, product labels and state and local rules come first.