How to Repair Electrical Shortages in Automobile Headlights

by Paul Vaughn

Diagnosing and repairing vehicle wiring can be a daunting task for a novice. This usually requires knowledge of how an auto electrical system works and the tools used to make repairs. Your vehicle's service manual will provide the essential information to help you make simple repairs to headlights.

Make a visual inspections of the wires in the headlight circuit (use your service manual to help you determine location and color of wire circuit). Any loose or corroded wiring can lead to a short in the headlight circuit.

Determine the gauge of the wire that is damaged and if it is a "hot wire" or ground wire.

Use your digital volt ohm meter to probe the damaged wire for an open circuit, which will show up on the meter as an infinite ohms reading. Determine how much of the wire is damaged.

Cut the wire at both ends and discard the damaged wire.

Determine the gauge of the wire you are working on and select the appropriate size wire connector. Position the wire in both ends of the connector.

Use your wire crimpers with the appropriate slot and crimp both end ends. Follow the same procedure for all damaged wire in the circuit.

Use your DVOM to probe the ground wire (usually a black wire). If the wire is undamaged, the meter should be reading battery voltage (12 volts).

Use the same procedure as you used with the hot wire to probe and locate and repair damaged wire.

Locate your fuse box and the headlight fuse. Probe the fuse by putting the red probe on the hot side and the black probe on the ground side. You should be reading battery voltage (12 volts). If not, the fuse is bad and should be replaced.

Turn on the headlights and see if both bulbs work in normal and high beam. If one or the other is not lit this indicates a bad bulb. Replace as necessary. If both lights are out, check the light socket for corrosion and use a small wire brush to clean the socket and put the light bulbs back in. If all else fails, take your vehicle to your mechanic.

Tip

  • check Make sure your battery is in good working condition before conducting your tests. If it is low it will be difficult to detect shorts.

Warning

  • close Do not check the battery with your DVOM. The meter is not designed to handle that much direct current and could be damaged.

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About the Author

Paul Vaughn has worked in the auto and diesel mechanics field for 10 years and as public school automotive vocational teacher for five years. He currently teaches high school auto tech, covering year model vehicles as old as 1980 to as new as 2007.