Tail Light Harness | O'Reilly Auto Parts Order Tail Light Harness for your vehicle and pick it up in store—make your purchase, find a store near you, and get directions. Your order may be eligible for Ship to Home, and shipping is free on all online orders of $35+. Check here for special coupons and promotions.Founded Location: Springfield, MO Tail Light Wiring Harness | AutoPartsWarehouse Take away the old tail light wiring harness afterwards. Step 4: Before installing your new tail light wiring harness on the vehicle, you must fix the wires that need to be attached on it first. Trim a little portion of an electrical wire, which must be able to extend from the actual wiring harness up to the tail light.