Turn signals activate horn ... sometimes

You know, I looked at all the wires because I was using my butane soldering iron and it throws off a lot of heat. I checked the immediate wires for melting. The insulation was good, but it is 38 years old and dried out. I will have to look further for cracking or splitting. I know I have to do it, but dammit! I just got a Grant steering wheel to go on straight without realigning the front end! Do you know how rare that is? Thanks for the idea!