Re: 66 chevelle heater cables diagram
The horn question for a 66 I can offer some info on, as my 66 came without at working horn.
I have the two spoke wheel. I bought 3 horn parts kits. None fixed it.
There should be pictures here somewhere, but I would buy the shop manual.
I replaced the turn signal cancelling cam, a major part of the horn. Still no horn. I had power at the spring loaded plunger and if I crossed it to ground with a screwdriver the horn blew....
After six months of messing with it, I figured out that power comes to the horn button via the wiring and to the spring loaded plunger that extends through the tube part of the cancel cam and then through the hub of the wheel It then contacts the against the underside of the belleville spring, (round spring disk thingie) when the horn is pressed.
The round disk thingy goes convex side up. The outer edge sits in a recess in the top of the steering wheel. The METAL PORTION of the recess in the steering wheel where the spring disk thingie sits is the ground path! Mine was nicely painted by the prevoius owner, insulating it. 30 seconds with a pocket knife and I had a horn!
There is also a ground wire that makes the ground across the two parts of the rag joint at the steering shaft connection that need to be clean and conducting.
A picture would explain it better, and if I find one later I will try to make it available.