Dont know about the Bonneville switches but we had alot of problems with the switches on our LeSabre. They are truely magnificent pieces of junk. Poor contacts. Id try a jumper wire in the switch plug first. Figure out which is hot wire and then jump around to see which is the up connection. It will throw a good spark when you touch the ground. If you have a tester locate that one also to avoid this. Multi meters are not that expensive and easy to learn how to use. Check for hot wire at 12 volt or 0-20 or 50 volt setting. Find ground wire by checking for continuity with ohm setting and touching ground (car chassis)with one wire and into plug with other wire. I think ground is black anyhow. The big wires probably RED are the hot ones. Then all the others are for up and down of all the various windows. Jump hot to a wire and see what happens. If nothing it may be up for a window thats already up so dont just sit there with the power connected move on right away until you figure out which function each wire controls.
Sorry to bore anyone that already knew this.
You can get used window assemblys out of any 86-91 Delta 88, LeSabre, Bonneville or 85-90 Regency, ParkAvenue, Electra. The junk yards may be full of them but they are crushing them pretty much right away because there is not much demand for older car parts anymore. You'll need a drill to remove the rivits and the whole thing will come right out. It can be put back in with bolts. Just make sure they are short so they dont interfere with movement.
Rear window assemblys are different they only open half way right ? If you need the little oval thingy that goes in the bottom of the window track and the arm of the lift , the ones from a used car on the rear windows will have the least wear - theoretically.