I can't figure it out.  I have a 93 s15 jimmy with push button 4wd.  When I
press the button, nothing happens, no blinking lights, no clicking.  It
doesn't even try.  If I am in revearse and push it, hi and lo blink, clicking
by glove box, but still no 4wd.  I changed the vacuum switch at the transfer
case.  No help.  Found a hole in vacuum tube at actuator under battery.
Replaced it and it worked fine.  A few hours later, started it, and it is not
working again.  Doing the same thing.  Anybody have any ideas??????