Jeep Wiring | Quadratec The wiring that comes along with those accessories can get out of hand quickly. Get your wiring under control with complete switch and wiring kits. If you have an older Jeep, companies like Painless Wiring make complete wiring, fuse and relay kits to replace every wire in your Jeep from the front to the back.Wiring Harnesses · Fuses & Relays Jeep Chassis Wire Harness - Engine & Transmission Wiring The purpose of a Jeep YJ wiring harness is to deliver electrical and other information to places your rig needs it. Many of the Jeep's systems have their own wiring harnesses. For example, your rig has a Jeep transmission wiring harness and an engine wire harness assembly. Unfortunately, over time, wiring harnesses can wear out.