I had the same as the others. Smelled burning plastic could never find the source, one day no lights or horn. Checked the fuses and all looked good, logged in here did a search and concentrated on the 30 amp fuse. Looked at it again and then I decided to pull it out and check it, It came out but one leg was fused to the box and then I could see a little heat deformation of the fuse. A little work and leg was out and new fuse in and no problems since then.
This site saved me a lot of wasted time replacing and tearing things apart.