I just picked up an 88 S15 Jimmy from a family member who's owned it since
new.  I noticed tonite the heater blows lots of hot air, but the vent
adjustment (from defrost to floor) doesn't work at all.

Its one of the vaccuum based units, and nothing seems to happen when you
move the slider - adjusting the heat setting works great, just not the
vents...

Now its stuck sort of between the floor and defrost, with the majority going
to the floor.  In winter you can see the dilemma I have  :)  Its not
important to me that the vent settings work again, but i'm more interested
in finding a manual way to force the diverter door over so that it directs
ALL the heat to the defrost.

Any insight on the easiest way to do this?  Or is there a known/easy fix for
getting the vaccuum driven divertor door to work again?  Either way will
work.  Is there an external lever that a vacuum actuator moves that I can
just disconnect and move manually?

I had this issue in my 91 K1500 with cable driven divertor - there was slop
in the lever so if you put it all the way to vent, it got "stuck" there and
had to get up underneath and manually push it back.

Your thoughts on how to get the most heat up on the dash as possible are
appreciated!

b