That's what I'm suspecting as well, the only thing I've got no is a "bulb-OK"-indicator... It is connected through the fusebox and to a connector with constant plus (also on the fusebox btw), I guess one of these are faulty/wrong then...
My car is an 84 (which is why I had to retrofit seatbelt-restraints as well), but the airbag-kit is from a 91..
About your light; It is most likely due to A) You've had the steering-wheel or belts disconnected with ignition on OR B) A wire is broken. Your car should have a diagnostic plug in the passengerside footwell where MB can check for errors as well as to put out your light (will of course come right back on if error isn't mended).
