Invest in a computer-safe test light and retire the old incandescent test light. The old one can damage sensitive electronics in your car.
This LED test light plugs into the cigarette lighter.
The old style test light can damage auto electronics.
Using a test light to check for circuit voltage is a tried-and-true diagnostic method. But if you probe a computerized circuit with your old incandescent test light, you can fry some sensitive and expensive electronics. Since almost every circuit in a late-model car is controlled by a computer, it's best to say goodbye to your old test light and invest in a computer-safe test light. These don't pull any power from the tested circuit. Instead, they plug into the cigarette lighter. A red LED means the circuit has power. A green LED means the circuit is connected to ground.