How to Wire up Lights in Your Hotrod! Then add in the years of corrosion at connections, wear at the light and dimmer switches and the amount of resistance in the circuit goes way up. So, use the right size wire. (See the lighting diagram below.) Tip: You can buy trailer wire cable to run wiring to the back of Related searches for headlight bulb wiring diagram 4 headlight wiring diagramheadlight switch wiring diagramfour headlight wiring diagramauto headlight wiring diagramheadlight wiring harness diagramheadlight socket wiring diagram3 wire headlight wiring diagramheadlight connector wiring diagram