As you can see in the schematic the 12V battery (or use other voltages) is connected with the plus at terminal T1 and minus at terminal T2. The contact 1 and 4 are connected together as 2 and 3 are ...

For some reason, dual horn relay wiring harness kits are difficult to find lately. The Eastern Beaver dual horn relay harness (review) that I’ve used before is no longer being made, unfortunately. But ...