A multimeter is favored over a test light for calculating voltage. Crimp connector crimping tool. Screwdrivers and other tools (as needed for your vehicle). pliers with a wire-cutting feature or wire-cutting pliers. Before beginning your installation, I strongly advise purchasing an inexpensive but delicate multimeter (left), such as this best-selling budget model from Amazon, and a wire crimp tool and wire crimp connectors (right). You'll get professional results, and it'll be a lot easier!