First things first! DISCONNECT BATTERY! Any time you're working with the electrical system in your car, it's best to disconnect the battery to avoid harming you and/or your car
First, you want to take the shift boot out. Squeeze the base of the shift boot on the left and right side and pull up
Should look like this when you pull the boot up. This gives east access to the switches through the console.
Push the window switches up from the bottom until they come out. They sometimes might be in there rather tightly so you may have to use some elbow grease, but be at your own risk.
Hold the base connector and pull the window switch out.
Should look like this when you pull them all out.
Here are all the switches and supplies laid out and ready (missing is the thin flathead screwdriver)
You want to put the screw between the casing and the actual switch itself. Work your way around until it pops open. Be aware of flying parts. It's spring loaded! Here they are laid out
Take the switch apart by putting a small electronics flathead screwdriver between the switch base and the external housing
On the end you are working on, push the base out from the housing. Repeat on all four corners. Notice I still have the other flathead between the housing and the switch base.
These are the contacts on the button that engage the switch to roll the windows down or up. Sand these lightly and put a dab of dialectric grease on there
Sand the corresponding contacts on the switch side and grease them as we'll. You can see where the button contacts if you place the button back on. Be careful not to damage the light bulbs!
Here is the button sanded and greased. Put them all back together and you'll hopefully have working windows again! Refer to the blown up switch photo (step 8) to see how it goes back together.
You're done! Comment if you have any questions or would like to suggest anything for your vintage BMW (besides oil changes and how to change your wiper blades)