Expansion Valve, yo

Anyone happen to know where and if there is an expansion valve for the a/c on our cars? I might have to work on it to get my a/c working correctly, and couldn't seem to find it nor could I find the evaporator or condenser or anything. Maybe I just wasn't looking hard enough, but the a/c lines just run straight from the compressor up the passenger side fender and through the firewall. I didn't really see anything.