climate control question

[cuda_dude]

is it normal for an air hissing sound to come out of the temp/fan/ac controls on the dash every time you turn one?

[4onFloor]

do all of your heating and ac controls work? some of the vent doors use a vacuum servo to open close them. one of the lines may have fallen off or broken. 9 times out of 10 it's the damn defrost.

[cuda_dude]

i think they all work.....but its every time you move any knob...so it shouldnt make that noise? and where are all of the lines located at? do i have to take apart the dash etc?

[4onFloor]

cant tell ya for sure, you'd have to look at a service manual

[89IROC&RS]

my car did this, what it turned out to be was the vacume valve on the back of the mode selector switch, it will start to seperate, and as you turn it, vacume will leak out around the seal. it needs to be replaced. you can test it by pulling the head unit out of the car, turn the knob till it starts hissing, and then push on the back of the valve assembly with your finger, to press the two havles together, and the hissing should stop, if it does, you found the problem. if it dosnt, then its one of the lines, unplug them one at a time, and cover the vacume port on the valve body, if the hissing goes away you found the line that has the leak. now find the point where its leaking, have fun