The pot-metal piece with the cam has broken in at the end of the slot. I don't think further repair is an option.

The P/N is: 004 545 0824

This one has the 3-position wiper speed switch and looks like it was the last version on the W115 going to the end of the series.

I do find a couple of other variants used on the W114's:

004 545 3224; 004 545 7624 & 004 545 7524

I don't know what the differences are.

I'm interested if anyone has a switch that will work. Functionally the switch also has headlight dimming (forward/back) & momentary flash brights (all the way back against a spring).

I am familiar with the worn cam syndrome the requires filing to fix; been there several times.

Interestingly enough, among those P/N's cited above, price new ranges from ~$170 to $300. This makes me even more curious about the functional differences.