Wire Function? 64 C10 horn relay-ignition

[Fredthecat]

What is function of the unfused 20ga wire run from horn relay 12V+ to ignition switch??

Wiring diagram for 1964 with V8 (page 379 of 60-66 Factory Assembly Manual) shows:

20 gauge black w/white stripe wire from horn relay (with 12ga Red) to Generator Harness Connector at engine bay firewall….

….then on cab side of connector a 24ga Brown w/white wire to ignition switch AND a 20ga Brown wire to instrument cluster connector ….to GEN lamp.

I have gauges so GEN wire may not apply.

What is function of the 20/24 ga wire run from horn relay to ignition switch??

Wire run is unfused. Mine is TOASTED on engine bay side...relay to connector!! Melted to a hard blackened mess. Yet worked.

Is larger wire needed? Any known short cause?

Thanks
Fredthecat