Mike- how many miles on the truck and what area of the country are you
from.  Reason- if you have some miles on it and are from an area where
moisture could have gotten on driver side floor area- I believe that
the wires run under foot on the drivers side.  Thus if you've got power
at fuse block and find nothing at the switch then you've lost it
between the seat and the fuse block.  On the S series Blazers(which
specialize in) this is a frequent problem and there are issues with the
wires that run under foot.  So in conclusion...power at the fuse block
and none at the seat-trace out the wires under foot.. May have to cut
out the bad and in with the new.  A wiring diagram would be helpful but
not mandatory.  If power at the seat then...possible/probable switch
problem. Good luck and Merry Christmas...Jerry@peru-motors.com