A) no power (+12V) to any of the power windows. The easy one here is from a fuse - check that first. Could also come from the wiring between the fuses and the main switch (located in the driver's door). Haven't run into this yet, but it's possible.
B) Bad switch. If a passenger window is the problem, there are 2 switches involved - the 'master' and the 'passenger' switch. If the driver's window works OK, it may be the passenger switch. Usually, playing with a bad switch will get the window to work - a little bit.
C) Bad motor. Had one of these. After replacing a switch didn't solve the problem, replaced the motor w/ built in gearing. (In hindsight, the tired motor may have damaged the switch, since the switch appeared to have overheated contacts.) The window would go down, almost all the time; but it wouldn't go up. Pulling the glass up by hand, and waiting between attempts, would eventually get the window closed (not something to do in a rainstorm!). The motor would run, kinda, but didn't have enough umph to raise the window. I bought an aftermarket replacement for about 1/2 of the dealer part price. I found that I did NOT need to do all the teardown (this on a 96 Astro van) the factory repair manual said! Just drill out the old rivets, unhook the electrical connector, (after removing interior door panel, etc.)connect the new motor, and bolt the new motor in place. Note that you'll need to get the window glass most if not all of the way up (somehow) to do this.
D) Wiring problem between the switch & motor - had some of this with an 85 Suburban. Check for this, before replacing the motor. Wiggle the wiring / connectors while attempting to operate - if something happens, inspect wires / connectors closely.
