70 intermittent wiper switch wiring

Just noticed my 70 intermittent wiper switch has a loose black wire that exits from the front (dash) side of the switch. It has part of a ground lug attached to the end. Schematic seems to show this wire connecting to chassis ground near the turn signal flasher, but the wire is too short for that. Anybody know if this is indeed a ground wire and where it is supposed to get grounded?

OK - the black pigtail wire from the intermittent wiper switch is indeed just an additional ground for the switch that gets grounded to the metal lower dash. My intermittent wipers were working, but the low speed was not. Opened switch to clean and adjust contacts, and now low speed works but intermittent does not. I am seeing 33k to 77k ohms across the potentiometer and my trusty shop manual calls for 6k to 7k ohms. Argh! Anybody got an extra D0ZB-17A553-B?