Trailer light issue

A buddy calls me to tell me he's putting new lights on his trailer.. it's a 1993 champion boat so who would be the trailer manufacturer?
He has brake lights, turn signal but no marker lights or running lights, any suggestions? Would it be a ground issue somewhere?

Most likely ground or bad connection. As far as manufacturer of trailer possibly TI. Trailers Incorporated.

Eazy loader may have built the trailer. There should be a plate with that info on the inside of the frame.

Run a ground wire directly from the vehicle to the frame of the trailer. This will solve your problem. The trailer is trying to ground from the trailer ball and that usually isn't adequate

if it was a ground problem no lights would work check for power on brown wire from vehical. if no power check fuse.if you have power at plug check down line till u find broken wire.

My buddy is so not mechanically inclined, I am thinking he probably screwed something up... Some of the lights worked before he started the operation. He's trying to swap the old halogen light a for LED. I can only imagine what wire he cut or what?

If he has any lights at all, ground from the truck is good. It should come through the white wire on the plug, not the hitch ball.
When I wired my last trailer, I hardwired ground to every light. If you use ground on the trailer, don't depend on star washers, take it down to bare metal for your connection.

what model and year is his tow vehicle?

if its a Ford f150 2013 or around that year check fuse 67. exact same thing happened to me, actually it continues to happen, go thru 3 fuses a year.

2007 dodge 1500 everything worked until he started working on the trailer except for the lights that were burned out. I think once I'm back in town, I have work cut out for me.

Make sure he did not blow the fuse in the vehicle. The running lights and marker lights are the same circuit. Most of the time when you have a bad ground when you turn on a blinker the lights will dim or they will all flash but having a good ground is important. Sounds like a broken wire, bad connector or a blown fuse on the truck.

Is he just replacing the individual lights or the entire wiring harness? A 1993 wiring harness would be in poor condition by now. I rewired my trailer & it eliminated all problems.

Have you tried disconnecting your trailers lights at the bumper BEFORE you dunk it? I always do this and fuses remain in tact.

I had to do exactly what DTA did. Problem solved. I still have extra fuses in my F150 from the time I was blowing fuses all the time.