Driver's Side Windshield Wiper Head Nut Cover

No, I have NOT had this problem on my car.

It is my conjecture that it is the particular position on one of the six points on the hex of the nut holding the wiper arm to the shaft that breaks off the plastic prongs.

The fact that it happened repeatedly, would mean that the dealer's service department just keeps replacing the cover without examining the root of the problem.

I would suggest that either you or the dealer's service department loosen and then retighten the nut so that the hex points will not likely land in the same position of the circle as before, but another position that would not likely cause the cover's plastic "fingers" to break off again.

 

Do you know if the dealership might have taken the wipers off? It's a requirement to get at some things towards back of the engine bay. The 3rd gen brake booster recall for example. If they had to do something like that it would be in your service records, there would be a paper trail that they'd taken it off at some point. Perhaps damaged at that time?

 

Not likely, unless the tech is a real dolt!

It's more likely the position of the nut, since it would place a particular "stress riser" that bears on a the plastic "finger" that would cause it eventually to snap.

The nut is a J.I.S specification M10x1.25 flange nut with 14mm wide flats on the hex. The plastic cover is must likely made of ABS (acrylonitrile butadiene styrene) plastic first developed by Eastman (under the trade name "Tenite").

Engineering failures are almost always more than one parameter coming together in a "one of a kind" situation.

Repositioning the nut will most likely alleviate the situation.

The fact that it happened twice means that the only "significant" variable is the position of the wiper shaft fastening nut. Not likely, but the nut might have a particular defect in that one of the 60 degree hex corners might have been deformed in either the manufacturing process or its installation. That kind of defect would also place undue stress on the particular plastic "finger" that snapped. Without examining the nut, I cannot be sure.

Not to brag, but to add credence to my suggestion is that I have over 30 plus years of accident and failure analysis in many types of mechanical systems.

 

It would certainly help if the OP posted a macro (closeup) picture of the arm/nut assembly.

SCH-I535