By taking the time to learn how your switch wiring system works, you can reduce your risk of electric shock or fire when working with switches. Tips Once you know how to wire a light switch, you ...

87 (red wire) connects to the positive wire on the electric fan. 30 (other red wire) needs constant 12-volt power from the battery. 86 (gray/white wire) goes to the ignition switch.

The diagrams and photos show how to wire up the fuel pump and oil-pressure switch to a commonly available, industry standard, ISO-type "1 Form C single pole/double throw" (SPDT) relay.

Neutral wire smart switch vs. no neutral wire smart switch Several of the best smart switches still need a neutral wire to complete a given circuit and stay powered 24/7.