Oil pressure Gauge and Parking brake light stay on...

Since your alternator warning light isn't also wrongly "on", I'd say that that's a good sign for the ignition switch not being the problem. Do the windows also work when those lights are wrongly "on" (and the key is "off")? If so, you might try using a different ...113 relay in the relay U (relay for key controlled services) position (bottom row, far RH side) as an easy test (i.e., first just remove the existing relay U and see if those lights go out; if so, then replace the existing relay U with maybe the horn ...113 relay to see if that fixes the problem). If a different ...113 in the relay U position has the same issue = not a good sign for the fuse-relay panel itself.

(All of the gauges also seem to be wrongly "on", too.)

 

Don't get the point of your key picture, but I'll repeat: relay U (relay for key controlled services) position (bottom row, far RH side) -- see the fuses and relay page in your OM.

 

Yes, that's trouble. If you have no wiring modifications, and the correct relay set installed, it almost has to be some sort of trace-to-trace short on the fuse-relay panel itself. It will take some $s, but having a better Guido, or GTCarParts, etc., fuse-relay panel isn't a bad upgrade for any Mondial. Good Hunting!

 

Yes, there's a battery rotary cutoff switch knob near the battery -- see page L3 of your OM (but, on the Motronic-equipped models like yours, this is a bit of a hassle to "relearn" things when reconnected).

Another very remote possibility is that a piece has broken off inside one of the relays controlled by relay U, and is shorting +12V onto the circuit that is normally +12V only when the key is "on" and relay U is closed. You could try unplugging each relay one at a time to see if it affects your problem (but the unreliability of the Mondial fuse-relay panels is well-known -- and unplugging/replugging a relay is such a violent act that it can wiggle things enough to alter an intermittent condition).

 

should replace all relays if still the metal Bosch originals, what they look like on the outside is what they look like on the inside...