I rebuilt this box probably three years ago and just got the mechanical s under the hood working. Had a problem with the heater control connection but have since replaced with a good one and tested with a NOS part. Both are responding the same. Issue is on OFF, both actuators close. On DEF, both actuators extend, and I get good air out the left defrost outlet, not the right side. Pushing the HEAT, the left actuator pulls in but little to no air in the floor vents. When I removed the heater control from the parts car, I believe I replaced the vacuum hoses on my car with the same configuration that was assembled on the parts car but not 100%. The hoses and actuators tested good with a manual vacuum pump. I have tried switching the hoses on the center actuator with no change. There are 7 vacuum pins coming off the heater control. This reduces to 5 vacuum lines a few inches along. Two with white stripe, two with red stripe and one vacuum source line. I am hoping its a vacuum hose issue and not something I may have missed upon reassembly. As I recall, there wasn't much to screw up inside the box however I still have success in that department at times.