a/c heater control questions

[deathphoenix99]

Does anyone know how the a/c heater control works, like how it engages the a/c clutch. I have a 94 chevrolet s10 with the 2.2 L. I want to add a/c, but I need to know how the switches works. I used a multimeter and the pins are open on the a/c and also on the blend and defrost. So I didn't know if it worked by resistance or how. Also if anyone has any pictures of a 94 switch with a/c on the backside. I want to look at the vacuum hose layout because I know on my switch without a/c, it looks different than those out of a 95 and newer on the backside with the hoses. I wanted to see if they are the same in the 94's whether or not they have a/c. Thanks

[deathphoenix99]

Does anyone have any ideas? or at least a good wiring diagram of the HVAC. Thanks for any input.