Lights, fuses, or connection? XT190

[HarleyChic]

Just purchased our 2010 Fun Finder XT190 RV 10 days ago. At first the electric brake was not correctly installed on the vehicle. A loose wire made the controller give error warnings such as OC even when the trailer was not hooked up. The brakes on the trailer were working and all the lights worked. When the company that installed the electric brake on the car fixed it, we also discovered a blown fuse in the electric brake. We replaced that. Now the driver side tail light on the RV is staying on. It will not blink or go off while hooked to the vehicle. Everything else works though. All of the other tail lights, turn lights, etc. Of course the dealership is closed for the evening and is on the other side of the state from us. They have recommended replacing the bulb behind the LED lights. It still works but only when my alarm on the car does! Any advice will be appreciated.

[LJAZ]

My first guess is that there is a bad ground somewhere. That can result in one circuit finding a path to ground through another circuit like your tail light - causing it to light. If you have a volt meter it's pretty easy to check. Could be other things but that's where I would start.