How to Troubleshoot Tail Lights and Turn Signals

by Justin Cupler

Faulty turn signals and tail lights are not only dangerous, but they can also lead to a stop by the police. There are several reasons these lights can stop working. The most common reasons are: blown bulbs, faulty wiring, bad fuses, bad sockets and bad switches. You will learn how to troubleshoot each of these items and what repair is needed to remedy your automotive lighting problems.

Check all the fuses related to lighting. Replace any blown fuses and recheck.

Remove the bulbs and check for any blown bulbs. Replace any blown bulbs and recheck.

Check the voltage coming from sockets; excessive corrosion or breakage causes a low voltage condition and will not allow the lights to reach full brightness. Replace any broken or corroded sockets and recheck.

Inspect the connection between the wires and the sockets. A bad connection can keep them from working. Repair any connection issues and recheck.

Use the wiring schematic to follow the wires and check for any breakage or burnt wires. Repair any breakage and recheck. Check all grounds in the circuit as well; a faulty ground can cause total loss of lights.

Check the brake light switch near the break pedal. Use a voltmeter to make certain the voltage is correct with switch engaged and disengaged. Check the grommet that depresses the switch as well. Repair any issues and recheck.

Check the headlight switch for proper voltage coming from it. Low voltage from this switch can cause the tail lights to not function properly or at all. Replace the switch is any issues are detected and recheck.


  • close Disconnect the negative terminal of the battery any time you are working on an electrical component.
  • close Do not cross positive and negatives as this can cause major electrical problems.

Items you will need

About the Author

Justin Cupler is a professional writer who has been published on several websites including CarsDirect and Cupler has worked in the professional automotive repair field as a technician and a manager since 2000. He has a certificate in broadcast journalism from the Connecticut School of Broadcasting. Cupler is currently studying mechanical engineering at Saint Petersburg College.

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