E28 electrical problems

I've got an 85 528e and it seems like the electrical system was on a time bomb or something. After the warranty expired, everything went haywire. First the fuel gauge always read "E" but the empty light still worked. Then the light for the OBC went out. Then the mirrors stopped moving. then the back passanger window woulnd't go up, followed soon by the rest of them. Then the tach stopped working. Then the power seats stopped moving. Then the revs started to fluctuate at idle, though I think thats the ICV. If anyone could throw some suggestions my way I'd really appreciate it

Hi, Pitbull-
You have about 17 separate problems.
The light for the OBC is an easy one. I bought a whole OBC on eBay for $20 and installed it in about 45 minutes. You can also just buy a replacement light bar and install it. You'll have to take out all your guages, which is actually easy. Put your hand on the plastic in front of the guages. Move your hand up. On the underside of the lip are two screws. Take them out. Telescope your steering wheel as far from the dash, and lower it as much as possible. All the guages will be ready to pop out. Reach your hand around behind the guages and struggle to disconnect the plugs at the back. Make sure you know where they go for reassembly. Once they are unplugged, the whole shittorea of guages can come out. You may have to use just a little bit of force to scoot them to the right past the steering wheel. Once they are out, the screws for the OBC are easy. Take the OBC out, unplug it, and replace the light bar. A replacement light bar costs about $20. Your fuel guage will probably magically work when you get it all back together.

Windows are EASY! Problems of the windows going up are down are entirely due to dirty contacts in the switches. If you just want the window to go back down, swap two of your switches.
The switches aren't screwed in or anything. They just pop out. Dig your screwdriver under the lip of the switch (try not to scrape up your center console), and pop it up. Once it's up, pull the plug out of the bottom side. It will probably be hard to unplug. If you're going to stick something between the plug and the switch to pry, use something non-metallic, you might blow a fuse if you short it out.
Pop up another switch that you know is good, and put attach it to the plug for the window that isn't working. It will work.
If you're really handy, you can take the switch apart and clean the contacts. Be warned that the moment you pop the switch open, two springs will fly out, never to be found again. If you don't catch them in time, you can buy replacement switches on eBay for about $5. Buy a bunch, and the next time you have a problem, replace.
Invite a friend over to watch. It'll be impressive, because this one is so easy, you'll look like you know what you're doing. I once swapped two switches in less than 3 minutes.
Good luck.

The power seats are famous for not working. I have no suggestions there.
Since you say ALL of the windows have quit working, you might have some fuses that are bad. My car, a 1985 535i, had most of the problems you mentioned. Before screwing around with all 17 separate problems, it pays to make sure the fuses aren't screwing you over. Here's the secret: when these fuses get old, they may LOOK fine, and actually be crap. Sometimes they will work, sometimes they won't. I bought a butt-load of fuses on eBay for $10 and replaced every single one of them. 95% of my troubles were over. Spend some money and replace fuses first.
If you can't afford the fuses...well, then you probably can't afford to drive an old BMW. That's the fact. The good news is, once you fix a bunch of this stuff, it stays fixed. If you can't find fuses at a reasonable price, PM me, I've got some leftovers from my own fuse extravaganza.
You can at least open the plastic fuse box, take a fuse out, make sure the ends are clean, and put it back in. You might play with the tabs in the fuse box to make sure they have some springiness to hold the fuse in place.

I was clueless when I got my car, and I got all of my info from this web site:
http://www.unofficialbmw.com/frame_e28.html
Get acquainted with it, especially the FAQ, and you'll save hundreds of dollars in repair bills in the space of a few months.
The idle control valve problems are dealt with in great detail on lots of sites. I'd recommend doing a google search.
Good luck, and welcome to the club!\
Flunky

You should also bone up on battery replacement for the OBC and service indicator board. It's a good thing to do while you have the gauges out. My cousin is pretty good with a soldering iron, so when we replaced those batteries (we made a little battery holder with long wires, so I can replace them myself next time with no soldering), I also had him re-flow the soldered joints on the back of the gauge cluster, which eliminated the problems I was having with my speedo not working.
Lots of these cars have speedo troubles: seldom do I hear about non-working tachometers. That's why I suspect your tach troubles are fuse-related.
Go find a buddy who is good with a soldering iron!
I started out with nearly all of the troubles you described. I'd fix stuff, and fix stuff, and nothing would improve. Finally, when I got replaced the OBC, EVERYTHING started working at once, and it was deeply, deeply satisfying. Hang in there.
Flunky