'95 SC400 plenum is not switching between modes. All the air is coming through the dash vents. I haven't driven the car in three weeks and I believe it was working prior to that. At any rate, it's not working now. I realize it could be due to either a vacuum leak or an electrical problem. I was hoping some of the members here might have some suggestions to help me narrow it down.

 

There is a door actuator most likely not switching.

 

No, both door locks and windows are functioning properly. I have yet to go through the various fuses to see it that could be the cause, but the fact that the display, the fan switch and the recirculation buttons respond correctly, I have my doubts that it is a fuse.

 

Sorry I was not descriptive enough. One of the blend door actuators in the hvac system is stuck, stripped,
or has lost power from the climate control unit. Or the climate control unit has an issue. Most likely the blend door.