Wiper motor wiring (park function)

[rix313]

I’m in the process or rewiring my race car and I have come up at a bit of a loss with the wiper motor. I’m using a modular fuse and relay box and plan to only have slow and fast functions via two switches on the dash. I have a BMW diagram however I think I’m missing the last link to make use of the park function. The small black/red wire which is supposed to operate the park and from faffing about in tests it seems this needs to be switched to earth once the wiper is in motion? Is this correct? I have spent what feels like an eternity searching online but haven’t found anything relevant to the E30 or similarly wired motors.