I have a 72 Chevelle Station Wagon. The rear window did not work when I bought the car. I started the repair job today and got as far as the window will now roll down but will not roll back up. I found a pink 18 wire that was cut, that is why it didn't work at all. The wire went to the fuse box on one end and to a relay on the other. What is the working purpose of the relay? Does it designate up or down?? Or is it there just to keep the power up due to the long wire to the back window. The front switch and the rear switch will roll the window down but not up. Anyone have any suggestions??

My 70 SS 454 has power windows, Behind the brake booster, If this is where your talking about. Behind the booster is a " Circut Breaker ", Overload protection for the rear window motor.
The GM window motors are insulated, The up-down switch reverses the ground to give the motor its rotation.
Thats what info I have,, Hope it may help.
Bob ACES--AACA

P.S.
My Red,70 SS 454 Sta. Wgn. Has a "Crank " rear window, I KINDA like that. When I leave the keyboard I am going out to the garage and put the glass back in the tailgate, I installed new Fuzzies in the tailgate and lubed up the gears and pivot points. If I can be of any help with your wagon, Just ask. Click on the blue in Robin-LS-5 thats my driver, As John Wayne would say """ Wagons Yoooooo "
Bob:thumbsup:

I have repaired my 65's rear window twice now, biggest problem with mine is old wiring and a bad ground. I am going to rewire it all the way to the dash this time and run a ground right to the Battery.

On my 69 wagon, the key will roll the window down but not up in the switch on the gate. I've never looked into fixing it.
I do have 2 NOS key switches I managed to find on ebay over the years. I'm thinking that if I replaced this switch, the key would make the window go up and down. Let me know what you find out.
fwiw.....My window works up and down from the switch on the dash. I've giotten into the habit of just using the dash switch to move the gate glass up and dwn.