wiper motor on a 68

My wiper motor on my 68' T-Bird will not shut off. I have checked the vac. connections at the swtich, and under the dash. Anyone ever had any experience with this type of wiper set up? They are run off of the vac. system and power steering pump.

on my 69 it sometimes stays on, i notice it mostly when ive just started the engine up. the on off is that round turning job , just use more force go from full on fast to off dont go from slow to off it might work or try givving it more revvs when you turn if off to build up the air vacume stuff.

Thanks! I will give that a try.