Old Henry,
I understand how a relay works. My question is that with a + ground relay both the primary circuit and secondary circuit can be fed from the same source. Then when you ground the primary circuit with a + ground the switch closes and supplies the negative full power to the load. Meanwhile the full load would not flow thru the horn grounding wire, although still connected. I understand the relays get hot, that is because a lot of amps is flowing thru it. Not a sign of being able to last. Do you ever see how hot the ignition resistor gets and it is on all the time.
My question would be what amp rating is given to horn relays.