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Troubleshooting No Runnings Lights After Optronics LED Combination Tail Light Kit Installation


Just installed the kit TLL9RK on my utility trailer per the video on your website. When I plugged it in to my 2019 Tundra, the turn signal, brake and hazard lights all work great, but the running lights do not work. I checked the brown wire connection and took it apart and re-connected it to make sure it was solid. Tried it again and still, no luck. My connection at the truck is clean. My ground wire is solid on the trailer. Any suggestions? Thanks!


Expert Reply:

Thank you for purchasing the LED Combination Tail Light Kit for Trailers under 80" Wide # TLL9RK!

To troubleshoot a certain light function on your trailer you definitely want to start off by checking your connections and grounds which is sounds like you've already done. After that the next step is determining which end of the wiring the issue lies on. To figure this out you can use a tester like the Brophy # F4CT on the vehicle side. For the trailer side you'll need to apply 12V power to the pins with either a different vehicle or directly from a battery.

Once we know which end the issue is on we can look at that a little closer. If it's on the vehicle side check that wiring and any fuses, and if it's on the trailer side you'll want to double check all of your wiring involved and maybe even apply power directly to the wiring on the lights so you know if the issue is the lights or the wiring running from the front of your trailer to the back of it.

Attached is an article that goes over troubleshooting trailer wiring for you to check out as well.

expert reply by:
Jon G

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