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Retire Your Old Automotive Test Light

Updated: Oct. 05, 2018

Replace your incandescent test light with a digital LED test light

test lightFamily Handyman
Invest in a computer-safe test light and retire the old incandescent test light. The old one can damage sensitive electronics in your car.

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Buy a computer-safe test light for auto trouble-shooting

Computer-safe test light

This LED test light plugs into the cigarette lighter.

Incandescent test light

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.