I've got a 7 Way Round To A 4-Way Flat LED Test Light Adapter that has the bottom light on, I don't have my instructions so I don't know what it means, it's on when the trailer is unplugged, Can anyone help?
I believe that just means there's power. You should be fine. I have the same one, but I don't remember what they are. But there is different leds to test different functions on the truck. Blinkers, reverse lights, brake lights etc. It's just telling you that your truck is working.