Poor Air Flow

I have a 90 LeSabre. The air flow through the car isn't very strong. In fact on occasion, the fan doesn't come on at all. I then open the hood and wiggle the connector to the fan motor which causes it to work. But not the way I've come to expect HI should or has been. In fact there seems to be a lot of air moving around inside of the dash but not through the vents, which leads me to believe that a lever is not opening fully. Any suggestions are greatly appreciated.

Check all of the lines that come off the fan for leaks :)