Here's some info gleaned in part from a German-published manual covering mid-60's vintage VW wipers and wiring terminal designations. The VW switch and setup for pre-'67, 6-volt VW's appears functionally the same as on 12-volt 544's as shown on the factory wiring diagram in my Scandcar CD of it. The VW manual explains the system rather well. And I got lots of experience in 1968 with the innards of the wiper motor on my 61 VW, which has a SWF-brand wiper motor visually matching the one in my late 544.

Features apparently in common: First, the wiper motor unit always has power connected to it, and always has a ground (earth) from it, regardless of the switch position. These are terminals 53a and 31 respectively, for the 544 motor. Second, there is a cam-operated switching feature internal to the wiper motor's geartrain that, when the wiper arms are in the parked position or nearly there, disconnects from the motor armature the power always supplied to terminal 53a. This provision is what keeps the wipers going after you switch off the wipers, until the arms are in the parked position. That internal, position-sensitive switch in the motor unit is part of what the so-called "brake" consists of.

The feature in common that gets the wiper motor going when you want it to, and keeps it running full-time regardless of arm position, is another wire (the blue one) from switch to motor that becomes live only when the switch is on, and the power is routed inside the motor unit so as to bypass that cam-operated parking switch. This blue wire on the 544 connects terminal 54d at the switch to 53 on the motor.

This leaves the green wire running between terminals 31b on both switch and motor, and the black wire running between terminals 31 on both switch and motor. The black wire is always connected to ground. The green wire is disconnected inside the switch when the switch is on, but when the switch is off AND when the wiper arms are also in the parked position, it grounds the other brush on the motor armature. I surmise that this helps the flywheel-like motor armature to stop quick so the wiper arms don't overshoot and get powered up again-- an electrical "brake". Otherwise what use would it have?

The internal switch failed on my 61 VW so as to short out the whole unit. The device includes a hard copper leaf spring that is pushed by the cam between two contacts-- the always live one when the arms are not parked, and to the 31b wire when the arms pass into the parked position. This copper leaf broke off and fell so as to blow the fuse and disable the wipers when I had to go from San Diego to El Centro (Cal.) on a rainy night, when the route was two lanes across the mountains. My later "repair" consisted of removing the copper leaf and doing without the self-parking feature, switching off as the wipers were a half-stroke above parked. Rob's 544 wiper motor could likewise be operated by a simple on-off, single pole, single throw switch, but the wiper arms would then coast to a stop like on my old VW.

I can't tell enough about the 120 car system from the wiring diagram alone to tell how the self-parking provisions compare with the 544 setup. It appears that the 120's have multi-speed wipers but the 544's clearly do not. I take it that "WS" feeds the washer and "P" is the power source terminal equivalent to 54 on the 544 switch. I reckon that "A" is connected to "F" internally in the switch when the switch is off. (This can be tested with an ohmmeter or other continuity tester.) If so, these two may be part of the park circuitry. Beyond that, I would test the 120 switch's terminals to find out what gets live, what grounds out, and what interconnects, in various positions. From the results maybe a partial equivalency to the 544 setup can be discovered and made to work.

Hope this helps some.