Left Trailer Brake Light Does Not Work on New Trailer Towed by 2001 Nissan Pathfinder

Question:

i just bought new trailer at lowes, my pathfinder has 7way blade connector. trailer is 4 way flat. park lights and flashers work great. however the left brake light doesnt lite while the right does. as i understand it if the flashers work then the brake lites should as well seeing as its the same filament.? am i in need of a 5wire adapter? someone said it may be because of seperate turn signals and brake lites. lowes was great, they even hooked up to another new trailer and we had the same issue.

asked by: Jerry B

Expert Reply:

The first thing you are going to want to do is test the 7-Way on the Pathfinder using a circuit tester like # PTW2979 if needed. The pins in the 3:00 and 9:00 positions are the turn signal/brake light pins. Have someone engage the left and right turn signals and then the brakes, 1 at a time, while you test with a circuit tester.

If all of the functions are correct on the 7-Way then that indicates a problem on the trailer. If the signals are not correct on the 7-Way then you may have a dirty or corroded 7-Way or there is a missing fuse or relay. Use the owners manual to locate any fuses or relays related to the 7-Way and replace as needed.

On the trailer side make sure that the main trailer connector ground is attached to a clean and corrosion free bare metal surface. Do the same for all of the trailer lights. A weak ground shows up when more load is applied like when the brake pedal is pressed.

This does sound like it is a dirty or corroded connector or a bad ground but it could also be an issue with the 7-Way to 4-Way adapter.

If all of the functions on the 7-Way are working, and everything appears nominal on the trailer then it could be the adapter. It may be pinned wrong, have a bad connection inside, or it could be dirty or corroded. If you are looking at the 7-Way side of the adapter the pin in the 1:00 position is the running lights, 3:00 and 9:00 are turn and brake lights, and 5:00 is ground.

Plug in the adapter to the 7-Way but do not connect the trailer to the other end. Instead, test the pins using a circuit tester. If the functions are not correct coming out on the 4-Way end then there is a problem inside the adapter.

expert reply by: Michael H