Hello All! I have a head scratcher for you. I believe that I have located the issue with my courtesy lights on my 1985 300SD. It is circling back to an open ground connection running through a 12-pin connector called C306. The electrical manual says that it is located at the passenger's footwell. There is no picture or further information. This 12-pin plug is used with the anti-theft, courtesy lights, and the alarm function on the central locking system. The door locks do work because the wires routed through C306 are alarm specific. In the passenger front footwell, I have the following under the carpet insert and black plastic panel:

Red plug for air bag
silver bosch box for SRS
black anti-theft control unit (also known as C1 in the electrical manual - it has an 8 pin and a 14 pin plug and it is unplugged as it is in my other car, probably because some point in the car's life it malfunctioned)

Under the right kick panel:
EGR control unit

Below the glove box insert:
Aspirator fan plug - 2 pin
HVAC plug - 2-pin
black bosch box for fan speed control
silver bosch box for climate control

I don't see anything else in this area? Is passenger footwell in the back? I don't recall seeing anything under the front seats or under the carpet. Is this a typo in the manual and is C306 somewhere else?

I am attaching a pdf file with the electrical diagram of the area of interest. The second page is from the back of the manual that says that C306 is in "passenger's footwell area".

I appreciate your thoughts. I was able to rig jumper wires today and got everything to work as it should. If I can find C306 (and I believe that it is unplugged), I will solve my problem.

https://docs.google.com/file/d/0B5mkYIZgTnn6YjNLeFZDLUJOSFk/edit?usp=drive_web

https://docs.google.com/file/d/0B5mkYIZgTnn6Nmd4UmNoZF9lYlE/edit?usp=drive_web