If I remember correctly those type motors park circuit only work with the right type of switch that puts power to the park wire only in the off position. Then a switch internal to the motor assembly opens when the motor gets to the park position. So ya you'll need to make sure that park circuit stays dead when your in the intermitent mode. Years and years ago I put a universal intermitent kit into an F100 I had. If I remember it was a little box with a pot knob that hooked between the trucks wiper switch low speed wire and the motor. You'd switch into low then adjust the speed with the knob from full normal to one swipe every 15 seconds or so. It was a cheap pos that only lasted a couple of months before it stopped working and I had to rip it out in order to get the low speed working again. Good luck with your project it sounds interesting, keep us posted.
Dave
