Beaumontguru! Thank you very much for your quick reply! "Grueling" does not sound like its going any fun at all! But its got to be done. Maybe it wont be as bad as it sounds. I'll let you know. Too bad it wasnt designed as a manual hand crank. Ok well thanks alot.

Sounds like you need to try to do everything humanly possible to jumper that motor first.

Here's some images I garnered from the Body manual,

 

In image 9-18, perhaps if you can get to the sash channels (2) you could unbolt them (2 bolts each) and allow the glass to slide down. Then you can get the gate open to remove the panel completely to troubleshoot.

Regulator

Those body manual scans are extremely valuable!  Good stuff, Mark!

I'm hardly an expert on this subject.  I've never even owned a Pontiac wagon, but I am lazy.  Being lazy means I don't want to do extra work if I don't have to, so I would ask myself a number of questions before I start ripping things apart (I tend to screw things up once I tear into them, so the ideal situation for me would be to diagnose the problem before I get the wrenches out, if possible).

First of all, do you know the history of the wagon rear window operation?  i.e. Was it not working when you bought the car, or did it stop working for you one day after making a funny noise or giving off a burning smell, or did it work when you put it into storage, but not work when you took it out?

With electric motors, the first assumption I always make is that there is corrosion at one of the contacts, or there's a bad switch (again, it may be easier to deal with those than to rip the motor out).  If you didn't witness some physical/mechanical problem with it (like a noise, the motor slowing down/labouring, smoking, etc.), I always assume the motor is good, and start going after grounds and contacts.  Like Mark said, it may be best to bypass all the other stuff and get a jumper directly to the motor, if you are able.

The safety switch piqued my interest, as it looks like something that would take power from the system if it's not satisfied (i.e. closed or open, depending upon how it's set up).  A wiring diagram might be handy, if you have access to that sort of thing.  If nothing is making any noise anywhere (like no relays clicking, etc), then it might be something to look into.

Anyhow... just trying to be helpful.  I'm sure experienced mechanics are chuckling at their keyboards right now, but the above is usually how I go about it, for better or for worse...

Best of luck with it, however you do it!! 

Good tips here about this window issue. If someone tried to open the tailgate with the window up I wonder if one of the latches my be partially opened causing the safety switch to be open also. Maybe push in on the tailgate to make sure its fully closed. Also if the motor is faulty you could try going for a drive and hold the window switch in the down position. A bit of shaking from a rough road may allow the motor to work if it has sticking brushes or a connection problem. At least if the window goes down enough to open the tailgate it will be a lot easier to diagnose.

Paul

I own 3 69 wagons so I've run into this a few times. Without knowing the circumstances of when it stopped working Id proceed in the following order

1 Check both power sources into the circuit (tailgate window motor needs power from BOTH the fused connector and the circuit breaker connection on the fuse block). Problems here would typically be a bad relay, circuit breaker or fuse. both have power with ignition to run or accessory move on to

2 Test for power coming into the dash switch for the window, in accessory or run you should have power coming in on the orange wire, pushing the switch up or down should then power one or the other of the two remaining wires.

3 Not sure about your particular year but you should be able to access the rear body harness in the rear near where it enters the tailgate behind the gas tank or by removing the driver side side panel. If so flex and giggle the wiring harness as close to the tailgate while someone operates the switch.

4 Now you have to remove the inner panel to access the mechanism. It is doable with the gate closed

5 Test power to the window motor, if power to the motor then bypass the safety (ground) switch and try the control switch.

6 If all the above are good than you have a defective motor. Be very careful removing it. Lock window in place with very tightly attached vice grip on a lever arm or cam that prevents movement. Remove motor assembly and replace with new unit. If you have two people you can, after removing      motor, press together on window from inside and out, remove vice grip carefully and then lower the window enough to open tailgate making reassembly easier.

Working in the tailgate is a bear and doing so with the gate closed is a bigger bear but not impossible