Originally Posted by dobrodan

You seem to be discovering all of the quirks of an ageing 111 at the same time. The horn honking is caused by the horn contact ring under the steering wheel shorting because the nylon bushings - Mercedes calls them seal rings - in the shift guide pivot are worn, or probably disintegrated. This lets the guide pivot rise too high in the column and contact the horn ring. This is an easy fix. The part you want is 111 997 12 40 (x2). You might as well replace the ball socket bushing on the shifter at the same time (111 268 03 92). Remove the steering wheel and shifter, horn ring, directional switch, etc and replace the bushings. You will likely have some old grease and nylon bits to clean out. Should take about an hour. Just don't lose the small c-clip in the steering column. No special tools are needed.