It is behind the glove box, so you need to open the glove box and then take it out.
Open the window ecu and look for broken solder joints.
Clean with rubbing alcohol and a Q-tip, apply flux and use a low temp pencil solder to redo all the joints.
If you have never soldered a circuit board before you must use a low temp soldering pencil and do NOT touch the circuit board with the pencil.

 

and that is instead of buying the $15 repair kit? So I take out the glove box and open the ECU and resolder what joints? This is just to fix my rear windows, I need some pics to get an idea, if possible

 

Driving a DIsco on a budget I would try and re-solder the joints first.
If that doe not work then order the repair kit.
No I do not have any pics, sorry.

 

i dont even know where to put the repair kit, where does it go? I dont like messing with the ECU, especially soldering the joints in the ECU, sounds risky business

 

all of your windows are wired to individual harnesses... are you positive that just the window switch is not bad? take out the switch for the window that for sure works and plug it into the harness for one of the rear windows... eliminate the obvious before you go tearing into more complicated fixes...

 

Good advice. When one of my back windows would not lower, it turned out just to be a bum switch. While I was replacing it, I decided to buy two front window switch's from a guy that was parting out his Disco ($5 bucks each). Now I have single touch lowering of all 4 windows. I also changed the positions of the front and rear windows since the 'upper' locations seemed a lot more intuitive to me for lowering the front windows since they were nearest to where my hand hangs when an arm its on the armrest. Now when other Disco guys get in mine and go for the window switch - they end up lowering the back windows. When they find out that it's a 5 minute job to swap locations, they swap their front window switch's to the 'upper' location as well.

 

This is assuming that you have ruled out everything else.
Once you get the repair kit it will have instructions.

 

well, the main switch in the middle console as well as the switch in the actual door doesnt work, so that means thats not the problem, since the other rear window doesnt work as well