Windshield Wiper Mechanism
Nissan did some strange things with the Z series and this is the strangest of all.
Ready for a mystery? Windshield wipers are pretty basic. You turn a switch and the wipers move back and forth. When you turn the switch off, the wipers stop and "park" at the base of the windshield. Every car has wipers and most of them work the same way. When Nissan began building cars, their wipers worked a little differently. When you turn off the switch, the wipers abruptly stop, then move in the opposite direction, stop again and then finally park. The reversing mechanism itself is contained inside the motor. It's an odd system but seemed to work well enough. However, if you do the popular wiper motor upgrade (like I've done), the replacement motor comes from a Honda Civic which doesn't have that "reverse rotation" feature and it parks the blades at the end of the cycle, just like all modern cars do. However... there's an unusual mechanism at the end of the wiper arms where they attach to the motor. Some people have described it as a "clutch" that is supposed to work in conjunction with the reverse rotation but can't explain how. Others says the mechanism is unrelated but can't explain why it's there. Most Z owners don't know about it or don't care as long as the wipers work. But the more I look at it, the more curious I become. It's a pretty complicated mechanism, especially for 1970, and I doubt Nissan added it because it looked cool or was a demonstration of their design prowess. It has to do something and I want to know what that function is, and so I made this page in the hope that someone will read it and be able to explain the function. Follow along.
This is the crank for the windshield wiper mechanism. The slot is where it attaches to the motor, which slowly spins it around.
The pin is where the wiper arm (that moves the rubber blades back and forth) connects. Typically the arm has a bushing that fits over the pin. As the motor turns, the bushing rotates and the arm moves back and forth. It's a pretty simple method but not for for Nissan.
At the center of the puzzle is this odd, cast piece of steel which resembles a cam of some sort. The hole in the center fits over the crank arm's pin, it it's off-center. There is a large tab at the top. The bottom is flanged.
The cam connects to the wiper arm. Normally a tab like that would somehow lock into the arm to prevent the cam from rotating within the arm instead of around the pin, but it doesn't.
Here's the crank, cam, and wiper arm assembled.
As you can see, the tab on the cam doesn't connect to the arm. Because the hole in the cam is offset, the length of the arm will change if the cam rotates inside of the arm instead of around the pin. The difference is only about 3/16", which isn't much, but why is it needed?
Next is a very odd "washer" with a tab on one side and a notch on the inside. It fits snuggly over the cam's tab, but the washer's tab doesn't connect to anything. If the cam spins inside the arm, the washer will also spin, so what's the purpose of it?
I guess ultimately none of that really matters because when it's all back together the wipers will move back and forth and I'll be able to see out the windshield when it's raining, but the mystery remains. What's the purpose? If you know, please email me