How to Fix Your Windshield Wiper Motors

Fixing balky windshield wipers can be as simple as a little grease, or as complex as installing a new motor.

By Mike Allen
November 9, 2010 11:54 AM

'Tis a beautiful day. Well, except for that one dark cloud that looms ahead, directly in your path through the countryside. Relax, it's a short summer cloudburst, and you'll pass through it in a minute or two. Raindrops dance on your windshield, forcing you to turn on your wipers. The blades, however, only twitch. Uh-oh. A few seconds later, the now indispensable rubber strips make a low-speed swipe across the glass, smearing the bugs and grit into a translucent paste, groaning and squeaking every inch of the way. And then the coup de grâce: The blades stop cold directly in your line of vision. The good news is that you manage to safely steer to the curb and wait out the shower. But now you've got a problem—your wipers have quit.

First Things First

Did you check the fuse?

Okay, Sometimes It's Not That Simple

Actually, a wiper assembly that refuses to move might have a simple blown fuse. But usually fuses don't blow on their own. Even at full stall, the current draw of the motor should be well below the fuse's rating. If the fuse is blown, odds are there's something else wrong, like a shorted wiper-motor armature or faulty wiring anywhere along the harness between the motor and the switch. Even a mechanical problem like a seized bushing can make a fuse eventually fail.

The fuse is okay, or you've replaced it with one that has the appropriate amp rating. There's still no action? With the wipers and ignition on, whack the motor assembly with the handle of a screwdriver or a rubber mallet. If that gets things moving, you've got a bad commutator or an open winding on the armature. When the motor parks, if the brushes are sitting on the bad segment, no current flows. Whacking the whole business smartly can sometimes jolt things into motion. Because there are often a dozen windings on the armature, the motor runs fine until the next time it comes to rest on the bad spot.


The mechanism on windshield wipers is as simple as could be. Inside that gearbox on the motor is a simple worm gear, spinning a ring gear and bellcrank that translate the motor's circular motion to a linear one, back-and-forth. Simple joints attach the transmission arms to the ­wiper pivot shaft, which is fixed to the cowl by some sort of pillow block. Lack of lubrication, ice buildup or simple corrosion takes its toll and can slow things down. A loose joint will leave lost motion, which can cause the blades to either flop around or, worse yet, catch each other and get tangled. The bad news: Sometimes it's difficult to access the area under the cowl. Worse news: If you go to the trouble of buying an aftermarket service manual in the hope that it will provide some guidance—any guidance—as to how to remove the cowl, it probably won't. Cars are complicated enough that not every single thing that needs to be taken apart can be fit into a bound book, and straightforward stuff like bodywork often fails to make the cut. (Think about it: Is it ultimately more important to know the torque values for the connecting-rod bolts or where all the screws to the cowl are hidden?)

A favorite friction point is the bearing surface between the wiper shaft and its mounting block, which is often nothing more than a steel shaft running through a hole cast in plastic. A cor­roded steel shaft can swell up and bind. It's not a bad idea to dismantle the mechanism, wire-brush off any corrosion and reassemble the whole thing with a generous dollop of silicone grease.

Disintegrating rubber mounting blocks and crumbling nylon bushings can leave slop in the linkage or cause excess friction that makes the wipers run as though they're coated with molasses. There's no recourse but to replace these. Unfortunately, some of these parts have no part number from the dealer, requiring you to replace an entire expensive assembly—or improvise. We bought a transmission arm, complete with bearing block and pivot, at NAPA for a fifth of what the dealer wanted.

Putting It All Together >>>

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