When I picked up the Toy, the seller had indicated the rear window didn't like to go up or down without whapping the panel where the relay sat.
Sure enough, it was recalcitrant at best.
Seeing as I've been getting a lot of input from the Yotatech folks, I shared my solution with them. Far better write-up below.
I managed to get the window down pretty readily, but I couldn't get it to go up for the life of me.
I assumed the problem was related to the "Rear Door" light in the dash being on. That was driving me nuts, it wasn't lit the night I picked the truck up and I couldn't figure out how to make it go off.
Ok, time to pull up the wiring diagram (which you can find online by Googling for the service manual. Most of the Toyota sites have sticky links to them too).
Looking through the Factory Service Manual's wiring diagram, I figured that out right quick.
LOCK the door (err, tailgate)... deerrrr.
I used to have a fullsize Blazer with an electric window and it didn't have a rear door lock, but the window wouldn't go up if the gate wasn't fully closed. I had assumed it was the door sensor that was acting up. And that's how past experience can get you in trouble! LOL
After that, though, it was still hit and miss - which it had been to go down.
The relay is behind the trim panel on the driver's side, and behind the driver's seat - about where a rear passenger's knee would go. Being a West-coast truck, it had zero external corrosion.
However, the [very thick] blue/black strip wire's relay-side connector was corroded, so I had to scrape that clean. The connector in the chassis-side looked fine, but a little blued from heat. Poor connections get hot.
After that, when I left the key on and twisted the relay 90 degrees each way, some of the sub-relays in it clicked on and off. The connection was still not solid.
Pulling/pushing the individual wires didn't help me narrow it down. But taking apart the relay and tracing the leads to the single relay clicking tracked down the wires I needed to pay attention to).
The ends of the connectors in the chassis side looked like they tend to connect with the spring-sides, not the broad flat sides, so I tweaked the ends of the connectors on the chassis connector to give them a slight bow at the front. Now the connection is decent and I can't make the relay click on and off.
Next time I get in there (when I do the front seatbelts), I'll add some dielectric grease to help it long-term.
It beats some of the solutions I saw with cutting open the relays, or creating your own relay array (the big relay box really contains 3-4 smaller relays).
3 weeks later and the rear window is working fine. Eeep! Did I jinx it?!?!