My car has suddenly started to blow through the defrost or top front vents only no matter what setting I turn the dial to. Any ideas for fixed or what I need to ask the dealership? I live in Canada and really need the foot or lower vents to work. It’s getting cold out there

 

Within the heater plenum is something called the "mode door" which, by its position, directs where the air comes out. It's position is determined by the computer based on the control position you select (assuming you don't have automatic temperature control). The computer sends a signal to a little motor that moves the door to the desired position. So where's the problem? Could be the control switch on the dashboard. Could be the wiring between there and the computer. Could be the body computer itself. Could be the wiring between the computer and the motor. Could be the motor, or could be the door. So there's no easy answer and somebody is going to have to get in there and start ruling out problems.