I had the same problem on my '71 145. The shaft that connects into the gearbox on the wiper motor broke on mine. The end of that shaft has a knurled pattern on it that is pressed into it's location. Eventually it gives up and that shaft comes loose resulting in no power transfered from the motor but it still runs.
My solution was to get a complete working setup out of a donor car and go through the absolutly most miserable car repair experience of my life replacing it.
Hope that helped.
Good Luck.
Wayne