Does that lever actually do anything?

  My van is an 84 without air conditioning.  I've got the other levers
figured out and they seem to function as intended.  Weird Logic that the
designers used to configure that system, but the bottom one has no
detectable effect on anything.  It is supposed to be controlling the rear
overhead vents, right?  But does it really?  Or is it something like the
heater control on an Air Cooled bus used to be..."wishful thinking"...
  Or is mine somehow disconnected?  Should I be feeling something inside the
van when I change that from open to closed..?
  Don Hanson