Inconsistent driver side vent temperature

I have dual zone climate control. Recently replaced the compressor, condenser, evaporator, and expansion valve. The system was working well for a couple of months. Now, the driver side vents only blow ambient temperature, unless heat is turned on. The passenger side works perfectly, whether blowing ice cold on A/C, or furnace hot on heat. The only time I can detect any temperature change in the driver side, however, is when maxing out the heater. When the climate control is set less that 85 degrees, the driver side air does not change temperature at all.