Need some ac/heater help

[hdff]

I just finished going thru my ac and heater. When I bought the ac cab truck the ac wasn't working and the heater core leaked. I refurbished the heater box and core and evaporator. I also put everything back under the hood, compressor,condenser, all of the hoses and hot water valve. Everything is back together except I have NOT filled it with R12 yet.. While driving with the vent on and outside air selected the air comes thru a little warmer than the outside air as to be expected. When I slide the selector to inside air the air gets hot like the heater it on. Does this sound right? When I slide the selector knob the vacuum opens the vent on the kick panel and closes the one under the cowl, and I assume makes the hot water valve move, but why would it open the hot water valve at this point? If I left the top lever on inside and slid the second lever more to the left to ac I would not think I would want the hot water circulating while the compressors is on trying to cool. Do I have something wrong? Am I thinking right? If not that compressor is going to work really hard to cool that hot air.. Any help will be greatly appreciated.. It looks to good not to work right...