Immediate popping of 25A fuse for the windows.
 

Any good diagnostic threads?

Don't tell me to search, did that. :rolleyes:

When this happened to me, some wires were touching behind the door panel, causing a short. I pulled the switch out and spotted the offending wires.

wires are touching a ground or each other. Start at the switches (pretty tight cluster and easy for a problem) and then where they go thru door etc.
Could be the switch itself....try the opposite switch in its place.

Has to be a dead short. Could be the wires worn through making contact with each other (most likely) or it could be the switch.

Any work done prior to this symptom or was it all of a sudden?

Window shares the same circuit as the power seats. I my case my power seat motor was grounding out on the steel frame after some work on my seats. Insulated it and all is well now.

one of the Window switches failed, had exact same problem a month ago.

I agree with all that there is a faulty window switch or there are wires in contact with each other or with ground. The cluster of wires is very tight where it connects to the switches, making it easy for unwanted contacts, I applied shrink tube to insulate the wire ends on mine to avoid a similar problem.
Here is a link with schematics that were usefull to me the last time I dealt with these switches: http://forums.pelicanparts.com/porsche-911-technical-forum/288567-power-window-switch-schematic.html
Jose

Yes, replaced rubber squegees a month ago. Do I have to remove the door panels to get the switches out or do they pop out?

The switches pop out, but I prefer to remove the door panels to gain working space and to avoid damaging the door panels. Once the door panels are out it is easy to push the switches out.

Had same problem. Cut ends of wires at window switches... placed new female spades... and heat shrink insulated up to spade. No more fuse replacing.

Ended up being an internal short on the passenger side switch. Put in another from "Brando's" garage queen. Tossed him some bucks, will buy another from our host.

Congrats!

Was able to fix w/o removing the panels. Brando had a cool tool that popped the switch out.

Funny, now my radio has a clock function that I didn't know about. Gotta find the idiot book as it is three hours off and displaying a March 14th date.

To add my 1982 911SC window-fuse issue findings to an old thread (that helped me, thank you!) to hopefully help someone else in the future:

Issue: windows fuse immediately popped when ignition was turned on (no chance to roll any windows up/down). Tried replacing the fuse and, new fuse popped immediately. I suspected a short somewhere and started with the easiest approach: the switches.

I was able to pull the three door window switches (two drivers door and one passenger door) without pulling the door panel (pretty easy to do). I made notes of the wire colors/connections before disconnecting them to test.

But, before testing the switches, I took a close look at all of the wires I had just disconnected and found two wires on the passenger door had a tiny bit of bare metal showing just below the connectors (the wires had rubbed together apparently and were now shorting together). I was pretty sure I'd found my issue!

I taped the wires, reinstalled the switches (without pushing them back into the door yet), installed a new fuse and, success! I now have working windows again for $0!!! I cleaned up and went for a drive.

So, as somebody mentioned before, take a close look at the wires after you pull the switches. My short was very small but, it was enough to cause the issue.