Mine runs but won't shut off. WAG is that whatever seals off the vacuum is toast. The mechanism that the cable connects slides easy. From reading here, not sure I want to take mine apart. I might look into some kind of ball valve that will cut the vacuum off and be able to operate under dash. I currently have bigger issues with the truck to get it road worthy.
That's probably just an issue with the slide switch on top. It just switches the vacuum to a different port to make the motor go to the park position and stop. If it isn't sealing correctly, or the port is plugged, then that might be the issue. Taking the switch off the top isn't that sketchy. But opening the body is not for the faint of heart. That usually doesn't go back together well.
