theair only blows out if the top and bottom but not the vents. i have checked all vac lines and they are all working good. i have partillay taken apart the dash and found the heat blend door is operated by vacum and the recurculate is elictric, but could not find where the things are that change the air flow. is there anyway i can manually change it to vents for the summer and back to defrost for winter ? how can i fix this ? does anyone have a diagram of the airbox ?