1999 Suburban HVAC broken

hey guys i really need some quick feedback on this one. i'm working on a 1999 or 2000 Suburban that our shop did a while back. the customer came back in and said the vents won't switch from defrost to dash vents or floor. i noticed that the antenna had been taped off but an extra pair of RCA's had not. i think they probably touched the open circuit board on the HVAC switch. does anyone know how to test to see which traces are bad since i don't see any burnt traces on the board? any help on this would greatly be appreciated. thanks.

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"I cannot teach anybody anything, I can only make them think."
-Socrates-

I could be wrong, but aren't those vents vacuum controled? I would look for a vacuum line knocked loose during the install.

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There is no such thing as free installation!

well, they actuators that actually change the vents around but it is a common problem for the hvac controls to have problems if you don't tape off anything metal behind the radio because GM thought it would be cute to leave the circuit board open on top. anyway, i have seen this a couple of times and haven't been able to fix one yet but was hoping someone here had seen the same thing and know how to fix it. well, turns out on this vehicle if you turn the knob all the way to the left and slightly press in on the switch it would switch over so i don't know if that was from the install or not. anyway, if you anyone knows how to fix these boards please post some tip action here. thanks.

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"I cannot teach anybody anything, I can only make them think."
-Socrates-