Dash Vent Problem

[porscheguy]

The dash vents on my '95 K1500 don't seem to work.

1. The fan works fine at all speeds.

2. The actuator on the driver's side works. It seems to control the flow to the defrost and foot vents.

3. The actuator in the middle, behind the ashtray, doesn't seem to work at all. Is this the one that controls the flow to the dash?

4. The temperature actuator also seems to work fine.

 

Is the center actuator the one I keep seeing advertised as the "blend door actuator?"

 

Is there a way to test it to make sure it is the part that has failed? I don't want to throw parts at this thing while guessing what the cause is.