Troubleshooting Various Lights Not Working on Enclosed Trailer

Updated 04/06/2020 | Published 04/04/2020

Question:

I have a 09 Carry On cargo trailer and for some odd reason I have a mix of lights out the actually lights are good but unsure of what’s going on. So the amber lights nearest the tongue the passanger side works but driver side doesn’t the red lights near the tailgate the driver works and the ossangwr side doesn’t. Lastly the the driver side brake light works but passanger side doesn’t and none of the lights at the top are on. My drivers side fender light works but passenger side isn’t there for me to test

asked by: Gary J

Helpful Expert Reply:

Thank you for all of the details! I know wiring can be a bit confusing but once we establish a few quick things about trailer light wiring I think you'll get a handle on it pretty fast.

First thing to note is that your trailer wiring should be separated into 4 different circuits;

Ground
Running/Tail/Side Marker
Left Turn/Stop
Right Turn/Stop

With that out of the way we can move on to troubleshooting. I think you either have some bad grounds, bad wiring connections, or you need to replace some bulbs - these are the most common troubleshooting solutions out there. Basically all of your running lights work aside from the front driver side so check the wiring to make sure it's all connected properly and then use a circuit tester like part # PTW2979 to see if power is making it to the light. If it is but the light doesn't work then you need to replace the light.

Then you'll simply follow this same procedure for all of your other lights as well. Since you aren't getting any stop (and I would guess turn) lights on the passenger side you may need to check the fuses for this on your tow vehicle. You can just as easily use your circuit tester to check the functions of your tow vehicle wiring connector to make sure all is well there.

I have attached some helpful articles on troubleshooting as well as a wiring diagram of a typical trailer for you to check out. If you end up running into another problem I would be more than happy to help out!