2000 Buick Lesabre Hot air on driver's side

With my a/c on, I get warm air on the driver's side and cool air on the passenger side. With the whole bottom of the dash out, the heater core is very hot. I can't find the heater control valve. I can't figure why one side is different than the other. A/c seems to work fine, but it is blowing the cool air past the hot heater core.