I just noticed the other day that the front passenger air vent in the middle of the car (right above the radio) is not moving very much air at all. When I have the heat on, the driver side middle vent moves quite a bit of hot air out but the passenger side middle vent isn't moving much hot air out at all. It is still blowing a little, but much less than the driver side. Could this be due to a leak in the system somewhere or a bad fan? I know nothing about the vent system in the car but I do know that it was working fine and then a day ago I turned on the heat and noticed the disparity. Would this be easy to fix?