i just put a heater core,blower and fan switch in my camaro and now my air only comes out the defroster (barely)when i open the flap by hand i can hear what sounds like a vacuum.i do you think i disconected something by accident?i didnt have to take the dash out so i can not see in there to good.gm dealer wants $300.00 so i would like to fix it myself.any help would be appreciated.thanks don winters