Guages not working
 

All my guages dont' work. The speedometer runs, but because it is hooked via cable to the tranny. No tach/oil/gas guages move at all. When you turn the lights on, the guages do light up, but there is no needle activity. The PO did some stuff to the fuse box... it has some fuse spots not in use, some other wiring b/c of a sound system. I looked in the manual, but it doesn't say which fuse actually runs the guages. Any help would be greatly appreciated.

Oh, it's a 1974 911S 2.7

sender for gas is at the tank, sender for oil pressure is on the engine...check below and to the right of fan, should see the wire for it. there used to be a wiring schematic for the car here on the pelican board...just checked and couldn't find it.
ryan

Yes, everything is hooked up, but I figure there's no way that ALL the guages would break. Even the tach doesn't work. There must be a fuse or something similar that powers the guage units, not the senders.

Turned out that it was the fuse for the rear windsheild defroster... like I said, the fusebox has been cheaply modified for subs and other stuff. I found this wire diagram though, which did help: http://members.rennlist.org/911pcars/WiringDiag.htm although I didn't find one for my exact car. I recommend you print a copy so that you will have it, even if you don't need it know, b/c it may be hard to find on the net when you want it.

that fuse is in the engine compartment right? the windshield defrost fuse.

No, it's in the trunk [front]. Its for "Relay for rear window defogger, fresh air blower control light of the rear window defroster."
You were right to assume the rear window defogger fuse is in the engine compartment, as it is.