I don't think it is mentioned on the install instructions that each tail light must have a good ground to the trailer frame. My driver side lights were not fully functioning and I was ready to take the kit back to the store for a refund. I called the manufacturer and was told each tail light must be grounded to the trailer via the two mounting bolts. Once I resolved this issue the lights work fine but I spent several hours trying to solve the mystery.

I purchased these to replace the lights on my trailer. Neither one of the lights in the kit works. The problem being that the contacts inside the socket don't make contact with the bulb. Checked the wiring with my probe and power is at both + contact points, but even after trying multiple bulbs, cannot find one that will make a good connection with the contacts in the socket. Completely annoyed at the quality, they're going back.