Do any of the windows work by using its on-door switch? There can be power there even when the driver's panel seems dead. When testing the rear windows, remember the child proofing cut-out switch on the driver's panel.

First suspect is that a switch has accumulated dried-up grease and dirt. They can be disassembled and cleaned and re-lubricated.

Second suspect is wiring, that which goes into the driver's door. It is subject to work-hardening and brittleness, also can get frayed.

The relay in the PW circuit is only a cut-out that closes when the key is in Position II (run). It's purpose is security.

Good Luck,

Bob

:>)