Voyager air vents to blowing
 

Hi all first time on the forum. I hope you guys can help me Voyager 2.8crd, front console and passenger and driver side air vents not blowing anything out but dash is o.k small side vents o.k and floor o.k. Car is in for full service on Monday but i would like to know what might be the problem before i have to take mechanics opinion on what the problem is. :confused:

HELP