its not to bad of a job to repair but you may have to remove the heater box to get too it,id check the vacuum supply to it first and see if the line has came off or the blend door is actually trying to move on it,a lot of times the line will come off and cause that to happen,it could also be the main control switch for that one that's causing that too happen,i see that more than i see the blend doors not working ,good luck on it.
