I can not get my 2002 tj air to blow out of the dash when I want it to. It will blow from the defrost then the floor and sometimes, just sometimes, the dash. I pulled the diaphram from under the dash an it does move when I select different positions on the switch and the flappers move freely under the dash but when I put it all back together it wont change blower positions. How do I check to see if it is the diaphram thing or the dash switch? Assuming I am going in the right direction here? Any advise or suggestions?