Need help diagnosing odd Power Window Issue

When I got my 99 with 80k miles, both power windows didn't work from either the drivers or passenger side switches. Power locks, memory seats, heat all ok. Now that I've sorted all the other larger issues with the car, I'm tackling the small stuff.

Here's what I've done so far:

-Removed drivers door panel
-Disconnected wire harness to drivers power window motor
-Used a multi-meter to check if drivers window switch is sending power to motor. Tested up and down on switch. Confirmed 12volts up and down. Switch seems to tests ok. Assumed motor is bad
-Ordered new power window motor
-Installed new motor, still not working.
-Disconnected window motor harness, used alligator clips to test window motor with a spare battery. Window moves up and down perfectly and smoothly.
-Again test switch and express down module with meter and harness to motor disconnected, all seems ok. I get up/down voltage, and hear relay clicks from module. Now I'm confused.
-Reconnect wire harness to motor, test, nothing. No clicks from express module, nothing.
-Use meter to test up/down on switch while harness is connected to motor, I get low up/down voltage.

Seems odd. Seems as when you connect the harness to the motor, you get no voltage from switch, and no clicks from express module. I repeat this testing multiple times, and I consistently get 12v up/down from switch, and hear relay clicking from express down module when harness is not connected to motor.

For reference, I test the removed stock drivers motor, and it tests ok.

What could it be? Bad express module, bad switch?

Weird one.

By Jove, I think I've got it!

- Do you have shop manuals, and therefore schematics, yet?
- Did you use that meter to do a continuity check on the Ground wire in the switch-connector?

My bet is that you'll find a broken wire in the "bending zone" going from the door to the dash - and of course the driver's door gets opened waaaaay more often than the passenger's...  It would explain all your symptoms & test results, because they wanted to save a dime on wire and didn't give the RH window switch it's own ground - it piggybacks on the lines coming from the master switch.  When you used a spare battery to test the motor, you provided your own ground.

I asked about keeping the express-down module because you have the door apart at the moment, and you've never had use of your windows...  If you look at my signature info, you'll see that removing that module is one of the many "Factory Annoyances" that I got rid of on my car.  Every other car I've seen with express-down uses a separate detent in the switch so you can push halfway for 'normal' and all the way for express.  These geniuses decided to simply go into express-mode after the switch is held for -get this- "more than 0.3 seconds".  Thus, it basically kicks in every time you want to move the window more than 2 inches.  
EDIT:  I found my original post:  I didn't remove the actual module, just 1 WIRE from its connector. 
(If you're interested, it also contains the procedure to delete the Brake-to-Shift function...)
https://rivperformance.editboard.com/t5428-delete-brake-to-shift-express-down-24hour-power-port?highlight=mirror

Even better, I went into my long-disused Flickr account to add a photo for the ashtray light and found the window schematic!   https://www.flickr.com/photos/24229483@N07/5328570671/in/album-72157618540359112/
It might look blurry when small, but it is sharp when you blow it up to full size.

Finally, depending on what you spent, it is still probably a good idea to keep that motor you bought "on the shelf".  

Mark

Thanks for the tips Mark, let me verify and test grounds/continuity on the switch.

Yes, I have the 99 Service manuals.

To quote Ted Knight in Caddyshack:  
WELLLLLL....  We're WAITinnnngggg!

Eldo wrote:

To quote Ted Knight in Caddyshack:  
WELLLLLL....  We're WAITinnnngggg!

Just got back from a 2 week vacation in California, I haven't had a chance to look much at it yet, will do this weekend hopefully. I'd like to get it fixed, as I have the drivers door panel off. Drives me nuts to have things apart, and not finished.

Ah, that explains it. What part of California?
I was down in the Bay after Christmas, just as the "atmospheric rivers" were starting to flow...

Eldo wrote:

Ah, that explains it.  What part of California?  
I was down in the Bay after Christmas, just as the "atmospheric rivers" were starting to flow...

We flew into San Fran (from Miami, FL) and stayed a few days there.  I picked up a 2022 C8 rental car (great experience), we drove to Napa, few days there, then on to Santa Cruz, Monterey, Pacific Grove, Carmel, Big Sur, San Jose. We were having lunch at the Post Ranch Inn (Sierra Mar) the day of the Bomb Cyclone. Crazy windy there.  Had a great time, and got to enjoy almost 1,000 miles in the new C8 Corvette.

Cool!  If you took 101 to Napa, you drove right through my home town on the way: San Rafael, with the blue-roofed Frank Lloyd Wright civic center.  From SFO, though, you may have taken the 'new' Bay Bridge...  I'm a little jealous, too.  You hit all the spots that I - just like the proverbial New Yorker who's never been to the Statue of Liberty - never got down to!     (Once Dad built the first cabin @ Tahoe, none of us ever seemed to go south across the Golden Gate.)

Update - Fixed the issue. I got a bit frustrated, and let the car sit for a couple of months. With a clear head this past weekend I further trouble shot. Turned out, is was simply a bad 25 amp circuit breaker in the fuse box. Even though I had months ago tested for continuity, and it tested ok, there was way too much resistance, and the circuit breaker wasn't allowing enough amperage to pass. Simple $9 GM part fixed it.

Now my power windows, and sunroof work perfect. I was also able to find (miracle) a brand new NOS drivers side door water deflector to replace the crumbling one. Got the car all back together now, and took it for a nice long drive. What a relief.