An Unobstructed View

| September 29, 2004

Don’t let failing wiper blades, arms or motors put you in danger.

A great fastball pitcher will tell you his secret is “they can’t hit what they can’t see.”
But in a truck you can hit what you can’t see. And it can hit you.

A clean windshield is critical in any weather but more so in wet and stormy weather when you need a clear view of the road even more than usual. But you can’t keep your windshield clean if your wiper blades, arms and motor aren’t in good working order.

We visited Kenworth of Pennsylvania in Kutztown, Pa., to get the advice and help of service manager Terry Meitzler. He showed us the simple process of wiper blade and arm replacement, jobs most truckers could perform easily. He also demonstrated wiper motor replacement on a 2004 Kenworth W900L, a job well within the capabilities of most truckers with a little experience in doing mechanical work. (We have used this model as an example. Work on your model may be different. Consult your owner’s manual or a mechanic.)

The location of the wiper mechanism high on the cowl of the truck demands a solid place to stand when you work. Use a good stepladder and follow sensible safety rules as you work.

Using the ladder is much safer than trying to stand on the frame rails or engine parts. Always use the ladder to get up and then check to make sure your footing is secure before stepping off the ladder.

Replacing the blades
Wiper blades are made of soft rubber, and truckers know that soft rubber quickly gets brittle and may crack. The result is pools of water on the glass that block your view.

Fortunately, if still new, poor performance may be caused only by accumulated grit along their edges. This keeps the soft but sharp rubber edge from contacting the glass the way it should. A careful wiping with a wet paper towel is often all that’s needed to restore performance. If grit is determined to stay, you may need to use mild detergent and water to get them clean. In this case, rinse them thoroughly to keep the windshield from developing a soap film.

Indications of worn wiper blades include a loss of pliability. This hardness may show up as edges that are permanently bent over, meaning they clear effectively only in one direction, especially after a long dry spell. Other symptoms include worn, uneven, feathered edges that produce streaks of water on the glass.

Fortunately, once the blades have lost their pliability or sharp, even edges, they are easy to replace.

The wiper arms should allow you to easily pull and retain the wipers off the windshield for service. Just gently pull them away from the windshield, and then insert a 1/8-inch drill bit into the hole in the side of the arm. When you release the arm, it will be locked 6-8 inches away from the windshield.

The blade itself consists of a flat, rubber insert with metal edges on either side incorporating a locking mechanism at the outboard end. To remove the insert, just use a pair of needle-nose pliers to squeeze together the metal edges at the indentations on the outer end. This will unlock the blade, allowing you to slide it out of the claws that hold it in several locations across the blade retainer. Slide the new blade insert into the outboard retaining claw with the insert turned so the locking grooves will go in last. Feed it carefully into each of the retaining claws across the blade retainer and then slide it in until the indentations at the outer end lock on the outboard claw. Pull the arm outward slightly and remove the drill bit, then release it.

Arm replacement
Wiper arms can sometimes get bent due to various kinds of road abuse, requiring replacement. They may also exhibit limited spring tension, causing the blade to fail to ride consistently against the glass. Also, wiper arms are sometimes replaced in order to use a different type of wiper blade and retainer.

Arm replacement is simple, but you have to be careful to restore the original alignment.

  1. Run a piece of chalk or crayon along the upper edge of the blade where it rests on the windshield.

  2. Pull the arm away from the windshield and install a 1/8-inch drill bit into the hole to lock the arm away from the windshield. Then install a socket wrench onto the acorn nut. Hold the arm with your other hand to prevent all the torque from being transmitted to the wiper linkage, and loosen the nut. Finally, remove the nut and washer.
  3. Carefully slide the arm off the splines and remove it.
  4. Install the drill bit to lock the new arm in the withdrawn position.
  5. If necessary, transfer the old blade and retainer to the new arm.
  6. Slide the end of the arm just over the end of the linkage driveshaft and then rotate the arm to align the blade properly with the mark on the windshield. Once it looks like it’s at the right angle, slide the arm onto the driveshaft splines. Remove the drill bit to release the arm and then check alignment. If necessary, reinstall the drill bit; then pull the arm off and turn it in either direction, and reinstall it to get the alignment right.
  7. Install the washer and then start the acorn nut onto the linkage driveshaft. Tighten the nut with a socket wrench while holding the arm against the torque with your other hand. Remove the drill bit.

Wiper motor replacement
After many miles, a wiper motor may fail, sometimes on only the speed you have used the most. But, before replacing a motor, make sure that’s actually the problem, as a failed fuse, switch or wiring could also stop it. A bad switch or certain wiring problems could also make the motor stop on only one speed. If the motor won’t work at all, always check for a blown fuse first and replace the one for the wiper circuit if it’s open before going further.

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