This is a re-post, As no one had so much as a "Too Bad" the last time.
My '88
560SL blows the 8 amp horn fuse at seemingly random times. The fuse circuit feeds the horns and the mirror heaters as well as the position control motor in the right hand mirror. I have disconnected one horn, leaving one (new) horn, and still have the problem. I have traced the wiring as best I could, looking for shorts & found nothing. I fear the problem may be in th sliprings at the steering wheel or in the wheel contact itself. MB runs power through the sliprings, and no relay is involved, unlike American cars which use the horn contacts as a relay ground. (A better way?) The car does have a remote start accessory added, but I cant find any interconnect that might cause my problem. Any horn experience/help out there? Appreciate any help.