I'd have this problem licked already if MB supplied proper wiring diagrams, however so far I've been unable to find a circuit-based wiring diagram for this car.

I know that the seat belt relay is bad (had courtesy light wires slammed in door) with all the usual symptoms of a failed relay, however all of the lighting is working normally from the passenger door, rear doors, and trunk lid.

Fuse box says Fuse # 11 controls Parking/Tail light right, warning buzzer, headlamp cleaning unit, illumination, license plate, instrument control elements.

Fuse #11 is fine, until I switch on the headlight switch, then it immediately blows, I can confirm a short to ground probing the fuse box with the headlight switch turned on. So far though, I haven't found the actual short!

I have the FSM on CD, but I'm not finding what I need there.

Is it possible for the seatbelt relay to be the culprit? I haven't pulled it yet, but it seems to be the only common link. I haven't read of anyone else having it cause a short or pop a fuse though. Before the wires were slammed in the door, I didn't have this issue, but a lot of other work has also been done to the car (window regulators, seat controls, etc), but nothing related to this #11 circuit.

I have disconnected the tail light assemblies and the license plate light wire harness. No change. I've also disconnected (removed) the warning light module in the fuse box with no change (supposedly this is a common failure point).

Has anyone else ever had this type of issue? Know where to find a better wiring diagram? Things to check?

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)