Just bought 1990 dakota extended cab, & here's the problem. The heater blower works, & the heater works, but I can't feel any air movement, or, no matter which button I push on the control panel, does the air direction change. Is the air deflection controlled by a vacuum, or electrical signal. I found another control panel under the seat, so I suspect the previous owner was working on this very problem. I don't want to tear it apart, right now, as it's pretty cold where I am. Just trying to get a little more educated, before I start working on for real.

 

It is controlled by vacuum. Check the vacuum hose under the hood.