97 A8 Quattro Power roof, PW, and cruise suddenly not working
 

I recently bought a 1997 Audi A8 Quattro. The windows, cruise control, power roof all worked fine, except the power roof switch was "sloppy" and would occasionally open when the switch was in the closed position.

The lights on the visor vanity mirrors would not light when the mirror cover was opened. I figured this was caused by a fuse and not knowing where to look at the time, I systematically checked (visually) all the fuses. They were all fine but I noticed that one fuse was missing. When I placed a fuse in that position (I did not record the fuse slot) the lights on the visor mirror worked. Awesome, except now the windows, power roof, and cruise control do not work. I was really frustrated because the windows were down. After scouring the web, I found that I could raise and lower the windows with the key in the door. So I was able to close the windows so I could at least use the car in the rain.

I was wondering if anyone here could shed some light on what might be a source of this problem, are the power windows, power roof, and cruise related in any way? What steps can I take to narrow down the root cause?

Also, any suggestions for what I should buy regarding a service manual or should I pay for access to an online service manual?

Thanks in advance for any help.

I can't know for sure without the wiring diagram, but the fact that someone has removed that fuse indicates there is a short in the circuit. If you remove that fuse does everything work again? If not im hoping it didn't smoke the comfort control module or something along those lines, thats the risk you take when buying a used car, you never know what you're gonna get.

As for buying a manual, i recommend every DIY'er buy a bentley manual, but if you're not familliar with engineering schematics you won't understand the wiring diagram. Audi diagrams are stupid confusing, even worse for porsche, so if you're not experienced in this field i would hand it over to the pro.

Oh, and the sunroof switch is what's causing the "lazy" sunroof. Its a potentiometer switch, so the contact tend to get dirty and send crappy signals to the motor. Some folks have had success by taking the switches apart and cleaning the contacts, personally, for $20 i would just replace it.

I'm not great at reading em, but after a quick look at my Bentley manual that includes the 97 wiring diagrams, those systems don't seem to share common fuses or relay locations. Just the sunroof and windows are tied together by the key closing both when all is normal...but cruise control?
I'm totally lost when trying to see what systems share the same wiring harness and/or connectors.
I'm also curious if anything would return to normal if the vanity light fuse was removed.

What auditech said about the sunroof switch is sound. If you do spray it with contact cleaner (the cheap solution) make sure after you cycle it a few times and clean it a 2nd time, you blow it dry with a can of air, otherwise it'll just get gunked up again. drying it after seems to work best, IMHO.

20$ for sunroof switch ?