Headlight Control Relay Question for 420SEL
 

I have a friend with a 1989 420SEL and his headlights no longer work, neither on high beam nor low beam. I suspect it is the light control relay, but we do not have a book on the car and the fues box diagram does not specify relay locations. We are told that the long black plastic relay is the light control relay. Two questions: (1) does it sound like the relay would be the likely culprit and (2) does anyone have a pin-out on the relay itself. I have a 12V test bench and can test the relay for function if I can find the pin functions. Any help appreciated.

Thanks,
Lance White