Gas Tank Conversion
I´m pretty sure your 89 is the same as my 88. On the back of the little black box on the window motor (opposite side from where the wires go in), there is a cap that can be pried off. Inside the box, there are two spade/bayonet connectors that can be taken out the back. Must be a french made motor, the bayonet connectors work backwards, you push where the wires go in and they slide out the back. Can be replaced with standard bayonet/spade connector and run out the back, where the cap was. And the wires, tied up, to clear the window and door opening/locking rods. If you hook up the wires backwords, the switch will probably work in reverse. If your worried about water getting in the box, just fill the whole thing up with a little silicon. I made a small loop and tied the cable to the motor with cable ties, so it wouldn´t break again in the same area.
The whole operation, could be really hard with the motor in the door. A 1/4 inch drill, will drill out the rivets pretty quick. For the motor and the small brace across the opening. There is one nut on the window bottom that has to be removed (don´t over tighten when reinstalling). A handfull of 1/4 inch nuts and bolts and a few lock washers will put things back together again. Getting the motor out, with the cable and tube is doable, it´s just a little like a puzzle and requires some time trial and error, gently. I didn´t have to bend anything. The book says one window rail (front) has to be removed, I got mine out without removing the window rail and/or messing anything up, just took a little while.
I think they changed the window motor in 91, pretty sure you have the same as my 88.
P.S. I made a little hook out of welding rod to hold the window up.