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Like most of its contemporaries, the Datsun 510 came with two-speed wipers-and no, the speeds weren't "Slow" and "Slower." It's a good bet it worked as well as any two-speed wiper of its day. In the decades I've spent working on these cars I must have seen one that actually had a "Hi" speed... but I sure can't remember it.
Maybe you have a wiper motor in your car that does have an acceptable high speed but it's more likely you have the Slow and Slower variety. If you've taken your wiper linkage apart, cleaned and greased it, made sure the ground to your wiper motor is in good shape and still don't have an acceptable Hi speed then I have the fix for you.
 1984 through 1987 Mazda 626s have a wiper motor that is very similar in design to the Datsun wiper motor. Three posts mount it to a plate, just like the Datsun motor. The rotating arm is almost the same as the 510 arm, except for the "stud" that attached to the wiper linkage. You'll find these motors one of two places: either in the engine compartment in approximately the same location as the 510 motor or in a plastic bag tucked into the cowl area. The plastic-bagged motors are usually in very good shape, not having been exposed to the elements at all. Either one will work. In fact, I've taken a motor from an '85 Mazda GLC and that worked fine, too. One of these motors actually faces the other way when mounted, making it a very good swap if you have a 300ZX VG30 intake manifold to clear or any other reason you might want more clearance in that area.
The first step in this swap is to remove the rotating arm from the back of the Mazda wiper motor and hold it up to the Datsun motor mount plate. Depending on which motor you end up with there are two variations of the Mazda mounting "posts." Both require drilling new holes in the Datsun plate. See Photo 1. Each version of the motor has a slightly different hole pattern, but all will fit the Datsun plate and it's easy to mark and drill the new holes. A little file work might be required, but it's a very forgiving modification. One of the motors will also require you to notch the Datsun plate to clear the Mazda motor. Again, pretty simple work with hacksaw and file.
Once the Mazda motor is bolted to the Datsun plate the difficult part of the swap begins. Although the rotating arms from both motors are very similar in design, you can't bolt the Datsun arm to the Mazda motor. It will be pretty obvious why once you look at them. See Photo 2. You do need the "stud" off the Datsun arm to connect to the 510 wiper linkage, obviously. The quickest way to do this is remove the Datsun stud and the Mazda "ball" and weld the stud onto the Mazda arm.
Grind the weld off the back of both arms, flush with the arm itself. Then you can either punch or pry both parts loose from their respective arms. See Photo 3. Nobody cares what happens to the Mazda ball (not even Mazda people) but make sure not to damage the surface of the Datsun stud.
You'll find that the Datsun stud is smaller than the hole created by removing the ball from the Mazda arm. It's not absolutely essential that the stud be welded exactly into the center of the hole, but the closer the better. Take some time and jig up the Mazda arm and Datsun stud to align them well for welding. The small gap between the stud and the arm is actually a good thing for fill welding because you'll be grinding the resultant weld almost flush with the back of the arm when you're done. See Photo 4, below.
 Why grind the weld? Because if you compare the "jog" of the Datsun arm with the Mazda arm you'll notice the Mazda arm is flatter. If you leave the new weld "high" it will actually come in contact with the bodywork when the arm rotates. Grind the weld almost flat (I usually leave about .020 or so) and there is no interference... or at least minimal interference that can be fixed by moving the offending "lip" on the body.
Revising the Mazda motor wiring to work properly with the Datsun wiper wiring was a challenge involving warm wires and melted fuses. I figured it out eventually (and deciphered how wiper motors worked at the same time!) and you'll be able to avoid smoking wires and 20A fuses by simply following the diagram provided. See Figure 1. The wires you see are what exists on the Mazda motor. You don't change a thing on the Datsun harness but every wire in the Mazda plug has to be removed and reinserted into a new location. Once again, follow the picture and you'll be fine.
A very small flathead screwdriver will remove the terminals from the Mazda connector. If you want the "Ultimate" terminal extractor for male and female Datsun terminals check out www.waytekwire.com and buy Item# 422 for $7.65. While you're at the Waytek site look around to find other cool things you might need. I find it a very useful website for wiring supplies.
Once the wiring is done you can plug the motor into the Datsun harness and make sure it operates correctly. You will probably have to ground the motor body to the car since it's not bolted down at this point. Turn the key to the "ON" position and pull the switch. You should have two distinct speeds. You also want to make sure the motor "Parks" when you push the switch off. This is important for the next step.
Disconnect the motor from the Datsun plug and attach the rotating arm to the motor. As noted earlier, it's important that the motor has "Parked" before installing the arm. Place the arm at the angle shown in the Photo 5, Page 5. Notice that the arm isn't quite parallel to the motor but angled slightly. This angle has proven optimal after a number of Mazda wiper motor installations.
Install the motor to the firewall/cowl, attach the wiper linkage to the arm stud (and enjoy installing that screwy clip) and plug it in. In most cases this completes the modification. I've had a few motors that didn't seem to ground properly. If the motor doesn't run once everything is bolted down and plugged in, try adding a ground wire from the motor body to the car chassis. That will probably fix the problem, but unless you want to drive around with a ground clip on the wiper motor you'll need to come up with a permanent solution. I've gone so far as to go into the dash and connect a ground to the black wire in the harness but I've also added a simple ground strap from chassis to wiper motor, too. Rather than tell you how to do this I think I'll leave it as an exercise for the Reader.
With this modification you'll have a wiper motor that looks like it belongs in a Datsun 510 engine compartment and also works as well or better than a new Datsun wiper motor. Enjoy your newfound ability to drive in a downpour!
DQ
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