Sometimes relays have a schematic on the parts box or molded/printed on the relay. If not there, maybe someone at http://www.aircondition.com/wwwboard/
has a schematic, or the relay manufacturers page might have schematics. I found several manufacturers schematics in German for various Klima relays, but nothing that applied to MBs. Good luck!
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E