Any ideas on where to start. One whole side of my trailer lights stopped working. The brake and turn signal lights on that side still work but no running lights. Please advise. Thanks.

first check the ground wire then go from there. u might also want to change the bulb. something in those lights go out on me too every once in a while.

I have lights on one side. Wouldn't they all go out if it was a ground issue? I also have multiple running lights on the right side and they are all out so I don't think it is the bulb.

the brown wire on the side thats not working is cut, broke, or not makeing a good connection, get a test light at the light see if you have power there if not work your way up to your plug, the brown is your running lights good luck

Check your wires

what make of vehicle are you towing with.

I have just the oposite problem, my running lights work on both sides but I have a break light on the right that does not work? Please help

If you have the folding tongue look inside of there for a cut wire. Its real easy to pinch a wire and not know it when you close the tongue back up.
Johnny

Bad bulb??

Guy's alot of trucks today have fused circuits for the trailer lighting so i would also suggest for you to check those fuses also,just because the truck lights work does not mean the trailer lights will if you have a blown fuse for the trailer.

on a 02 for f150 wonder which one that would be

cause my left side blinker and brake dont work i hooked up a a tester and it said that sides not working where would i start on the truck? fuses?

Check your fuses under the passenger side kick panel.

k thanks just gotta figure which one it is

Under the hood, driver side, behind the main fuse box and just in front of the firewall check for a small box. It will be not much wider then the mini fuses and only long enough to hold 4. You may or may not have it on an 02. On my 98 150 it is there and there is no documentation anywhere about it but it controls many the lights on the trailer.