No ideas, other than a defective switch. Here are some diagrams for a 69, if you don't already have them: http://www.firebirdnation.com/forums/topic/246341-1969-pontiac-firebird-wiring-diagrams/

 

yep could be also be a blower relay but definatly sounds like the the switch

 

I have pulled the master switch and the blower motor switch out of the car. I pulled apart the master switch and cleaned it up. I am now able to adjust the speed on the blower motor, and turn it completely off.

But i'm still not able to engage the AC clutch.

Does anyone have a wiring diagram where of a 68 firebird with AC.
Or at least knowledge at where the wires go...

2 of the wires go to the blower switch (gray and yellow). The power wire from the switch, and then there is a fourth wire (green) that goes back into the dash. Something happens (theres another switch back there....and somehow this green wire comes out looking tan. Can anyone tell me what happens back inside the dash at least?

 

Here is a link to an installation guide for a/c into a 68 Firebird/Camaro. It has a partial wiring diagram and lots of photos. Might help.

http://www.classicau...-1055Manual.pdf

Edit: another diagram with green and tan wires...this is probably what you need. It was apparently drawn by some avid 68 owner who is good at making diagrams. I think the item you are having trouble identifying is either the low temperature cutoff switch (performs a defrost operation) or the diverter flap switch (makes sure the flap/door is in position to allow the evaporator to get air flow). One has a dark green wire and the other has a light green wire. I was confused as to what he means by "low blow", but I think that is just his term for a/c cooling.