Troubleshooting Trailer Blinkers that Both Blink When Either is Applied

Updated 05/08/2018 | Published 05/05/2018

Question:

I need an answer. My trailer works fine with other vehicles but not the Curt harness on my 2006 Toyota Rav 4. Both tail lights blink at same time when turn signal activated

asked by: John

Expert Reply:

First thing you should do at this point is test the 4-way of the wiring harness with a circuit tester part # PTW2993 for voltage on all of the right pins when the taillight signals are being applied. Just like in the video I attached.

I think there's a short between the stop/turn circuits which is causing them both to activate when either is turned on.

If the problem is on the vehicle side then I would first recommend you double check how the harness is installed on your vehicle, make sure all of the connections are good and tight. You should check all towing related fuses and relays as well. What you described can sometimes be due to the converter box shorting out.

What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the # 3808 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test the output side of the box to see if the current is making it through the converter. If not then the problem is that the converter box has shorted itself out and would need to be replaced.

Before you replace it you will want to inspect the wiring of your trailer to see if you can find anything that would cause the box to short out like corrosion or cut/exposed wiring. These boxes don't usually go out unless there is a short on the trailer that takes it out.

expert reply by: Jameson C