Bench Testing Trailer Taillight Assemblies To Determine If The Taillight Is Faulty

Published 07/22/2021

Question:

2018 Jayco Jay Feather 19XUD..Tail/Turn/Stop light is dim on right side only. All other lights are the same brightness on both sides and the TV lights are all working normally. Checked wiring at light and where the three wires connect to trailer wiring and all connections are good. Replaced the right side tail/turn/stop light assembly Command 003-619 with part from Command and now with lights on, brake light illuminates all the time and turn not working. Put original light assembly back in and everything works as it should, except all three are still dim. Any help would be greatly appreciated.

asked by: Chris

Expert Reply:

With everything that you have it sounds like the best course would be to first bench test both of your lights. As the lights perform differently when both connected to the same wiring this will help you to determine exactly which taillight is performing properly and it will narrow down the trailer wiring error.

First with each light grounded to a 12 volt battery you will want to add power to the other 2 wire circuits. One will activate the dim running lights and the other will activate the brighter brake light/turn signal. As it does not have the flasher relay it will just be a solid light at this time. With the confirmed working light you will then be able to address the taillight when connected to your 2018 Jayco Jay Feather 19XUD.

Before testing the lights installed on the trailer you will want to use a Test Light # PTW2993 to confirm that your 7-way connector is functioning properly. I have included a picture for the 7-way vehicle side connector to know which circuit to test.

Once you have established that the issue is with the trailer you can test the trailer wiring to determine if it has a short or damaged ground connection that is causing your issue. Jumper wires directly to the ground connector will help you to determine if there might be a ground connection issue.

expert reply by: Bud M