That IS weird. Right turn only? Would have to be an electrical issue, since both blend door actuators (motors) are gear driven and are oriented with a front/rear axis. In other words, the doors don't rotate sideways, but rather front/back, so a turn couldn't physically open or close them. But I can't think of anything electrical that would be tied to a hard right turn.
I agree with alrock; run the calibration procedure and see if both blend doors rotate fully during that process. You can look up under the dash on the driver side and see both of them (there's also a third actuator, higher up near the top, that controls the output direction (dash, floor, defrost), but the two lower ones are the temp control.