Trailer Wiring Wiggle Tester Instructions

Trailer Wiring Wiggle Tester Instructions


When you have a lighting issue on your trailer, be it a fuse that keeps blowing or lights that flicker or stop working intermittently, it can be very difficult to find the source of the issue. Intermittent faults are tricky to troubleshoot when the issue comes and goes at random. You may suspect a short or a bad connection is causing the issue, but pinpointing the location of the problem can be challenging with wires routed through so many inaccessible areas of a trailer. That's where the Olsa Tools Trailer Wiring Wiggle Tester comes in!

How it works

Olsa Tools’ 4-Pin Trailer Wiring Wiggle Tester works by detecting small changes in the trailer’s lighting circuit: normally the resistance in the lighting circuit should be perfectly unchanged, but if there is a bad connection or an exposed wire occasionally getting shorted, the "wiggle tester" will detect it. Simply wiggle the wires along the trailer and when you wiggle an area near a bad connection or a short, the change in resistance will cause the tester to beep, helping you to pinpoint your issue so you can repair the problem.


  1. Disconnect the trailer connector from the vehicle and replace any blown fuses.
  2. Connect the top side of the tester to the vehicle and the bottom side to the trailer. Don't worry, the two circuits are now isolated so any faults in the trailer will not blow a fuse in your vehicle.
  3. Turn your vehicle marker lights on. This will provide power to the tester. There will be an audible beep and a visible indicator light when the tester turns on.
  4. Press the SELECT button to cycle through the three circuits (Marker, Left Turn, and Right Turn) until the indicator light is beside the circuit you wish to test.

Note: There is no separate circuit for brake lights as braking is indicated by turning on both Left and Right turn signal lights simultaneously.

Note: The trailer lighting will not illuminate while using the tester. To prevent any further damage, the tester provides only a small voltage, similar to a resistance tester on a multimeter, which is enough to detect a problem, but not enough to illuminate the lights.

  1. Wiggle and shake the wires, connectors, bulbs, and all electrical components on your trailer. If you wiggle an area where there is an intermittent short or a poor connection, the tester will make a loud beep and the light will flash indicating that you may have found the location of the issue.
  2. Once you have located the issue, disassemble this area of your trailer and repair or replace the faulty wire or connector.

If you have any questions or issues, please reach out to us at or call us at 1-877-252-OLSA (6572)

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