R50 rear wiper won't stop, one-speed only

[MinisterofDOOM]

I've got a 1997 R50 Pathfinder I recently bought. It is in great shape mechanically, but the body is a little rough and the rear wiper is mostly unusable.

Specifically, the rear wiper turns on, but only runs at full speed, won't turn back off, won't run at intermittent speed, and doesn't "park" correctly.

I've replaced the switch, I've cleaned all the contacts, I've watched the thing run, but the only external positioning sensor I can find appears to handle the park position sensing (little matsushita tact switch).

Anyone familiar with this issue? Should I just replace the motor? I can't find a relay dedicated to the rear wiper anywhere (either physically or in schematics). Is there one I'm missing somewhere?