Did it for a hundred bucks, but if I had access to a junkyard with a minivan tailgate wiper motor, maybe 25 bucks (I already had some old push-pull switch).... These motors like from a backhoe, or a speed boat swing an arc of about 110 degrees. The transmission is part of the unit. I cut the v shaped arm off the back of my wiper motor and welded it to a 1/2 " nut and tapped in a couple of set screws. Slipped the 1/2" nut over the knurled wiper shaft that rocks 110 degrees and kept my vaccuum arms and all the gear under the dash. The rocking back and forth of these type electric motors mimics the action of th vaccuum wiper. I think the system I'm talking about is called a 'self reversing motor'. It works fine, but maybe it's just me.... I enjoy an engineering project to tackle after work.