My air conditioner stopped blowing through the a/c vents,if i switch it to defrost and turn the knob to the cold side I get cold air coming from the defroster also if I get cold air from the floor if I switch it to that mode. I'm not getting any air from the a/c vents even if I just turn it on vent. Any clues? I did a search and read about a vacuum line being off but I checked mine and they all seem to be intact.