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Bizarre windshield wiper issue

Wondering if anyone has any experience with what seems to be a very odd problem.

Our windshield wipers work just fine. They cover the entire surface of the windshield. Not a drop remains.

Until the vehicle starts moving.

At about 15-20 mph, the amount of surface covered by the driver’s side wiper begins to decrease. At full speed (50+), close to half the intended surface is not being cleaned by the wipers. This creates a residual puddling from the region that is not getting wiped.

It’s weird to explain. I tried to illustrate this in an attached image.

Where we live gets 60-70 inches of rain a year - almost all of it between now and March, and so this isn’t really something we can just “deal with.” Rain-X helps, but this is ultimately a safety issue.

It’s also worth noting that we replaced the windshield about a year ago thinking that perhaps a sub-standard factory windshield (Safelite) was to blame. Disappointingly, a couple months after that when we got a rain substantial enough to need the wipers, we realized that the same issue was still present.

Again, the attached image tries to explain this visually.

Look to see that the wiper blade assembly is facing the right direction for the air foil to be working in your favor.
– it sounds as if the blade is either backwards, or has no air foil ( a universal blade ) and the air flowing up the windshield at speed is therefore lifting the blade from the surface on the downstroke. ( they’re hydroplaning )

If you can’t tell by looking , perhaps you’re not sure what I mean by that, ask a good parts house or your local tech to check the direction of your blades.

The fact it touches the entire windshield when you are stopped or going slow suggests to me the windshield is most likely OK when Safelite put it in. What I would look at as a possibly is the spring tension on the wiper arm that holds the entire mechanism down. Rarely is this a problem but it is possible the spring has gotten weak or the attachment pin for the spring has bent and is reducing the amount of tension to the windshield. One more possibility, though I have never looked at a Windstar, is that maybe the arms look interchangeable but in-fact are left and right designed, whereas Safelite might have installed them on the wrong sides. Usually this cannot be done on newer cars but was common on older ones.

Thanks for the quick responses …

@ ken green - the problem has existed for numerous blades over a few years. Or are you referring to the part of the assembly that belongs to the vehicle?
@W30post - I can check this, but Safelite was the factory windshield (we have a replacement now) and the issue is the same now as then. Also the blade size is different for L and R wipers - fortunately a misplacement here should be pretty obvious. But I’ll check.

W30 is refering to the spring inside the arm. The arm being the ‘‘vehicle part’’ and a definite probability.

I’m refering to the wiper blade structure, not the rubber edge but the metal frame and fingers that hold the blade.
The upper portion of the framework should have longer and shorter sides. The longer side should face forward. It is the airfoil or wing that helps the blade stay down as it moves forward on the down stroke against the rushing wind.

el-cheapo blades may not even have that and just be equal sided.
A reverse mounted blade will have a negative effect and lift from the air flow.

Back to the arm portion ;
A wiper arm should have a slight bow to it and not be exactly straight from the pivot to the blade.
An arm that is straight will greatly effect the resulting spring tension on the blade.
If your arm is striaght or if you’re unsure, you can simply bend it some more with your hands.

Where the arm holds the blade…
Check thet the arm/blade attachment is exactly perpendicular the windshield. An arm that is slightly twisted will also effect the downstroke results.
This can also be fixed by bending. you can use a crescent wrench to grab the arm and twist it back correct.

It sounds like an airflow issue. Try some RainX Latitude or Bosch Icon blades. They work real well on my cars.

i think the wiper am might be loosen its spring tension time for a new wiper arm

Your blade is being pushed up off the glass by a layer of compressed air flowing over the windshield. The flow, following the profile of the car, is called “laminar flow”.

Yes, I’ve had the problem. Rubber-booted winter blades are particularly problematic on my car.
The solve the problem, I use blades 2" shorter on the driver’s side (24" instead of 26") and on the passenger’s side 16" instead of 17" to reduce lift, and I’ve also switched to the blades with no frames. They’re a bit more expensive, but they solve the lift probem entirely.

Thanks all.
@doubleclutch - RainX blades are the current ones and the issue persists :frowning:
@ Big Marc - will check that, too
@ the same mountainbike - that sounds like a good solution, too. Thanks!

Are they specifically Latitude beam blades, and if so, did they somehow get installed upside down? (I have to look at mine to see if this is possible). RainX has several different models of blades.

Air is pushing the arms up. Try replacing the arms.