Relay Wiring Diagrams | the12volt Dozens of the most popular 12V relay wiring diagrams created for our site and members all in one place. If you need a relay diagram that is not included in the 76 relay wiring diagrams shown below, please search our forums or post a request for a new relay diagram in our Relay Forum. Light Switch Wiring Diagrams - Do-it-yourself-help Multiple Light Wiring Diagram. This diagram illustrates wiring for one switch to control 2 or more lights. The source is at SW1 and 2-wire cable runs from there to the fixtures. The hot and neutral terminals on each fixture are spliced with a pigtail to the circuit wires which then continue on to the next light.