W123 Horn Trouble
 

My 1984 300D has developed what appears to be a minor but annoying
electrical problem. When I turn the steering wheel to the max right or
left it sets off the horn. I took the steering wheel cover off looking for
loose parts. I cannot find anything but then again I am not sure what I am
looking at. There are is a wire on the left and right inner side. Horn works fine on each side when the cover is depressed. New contact switch needed?

Try taking off the steering wheel. The brushes might have degraded and there is probably bit of them floating around the contact ring. Also check the ring on the back of the steering wheel for issues.

The wires that feed power to the horn are attached to the turn signal stalk. Maybe they're frayed?