So last night went to swap trailers with my old man he has 2009 Lowe trailer with like 0 miles on it and since I head to Wyoming in a few days with the boat wanted a good reliable trailer with brand new bearings and tires. Here is the problem. Dad has a 2008 chevy 1500 plugs in the trailer lights all the light come on till he hits the brakes and it kills the left half of the trailer lights. I have a 2010 F150 plug the trailer in right side comes on left side doesnt even turn on. We opened every light on the left side and tested them they all have power but none of them turn on. Their is power at the plug in at the truck and all the way back so why in the hell don't they turn on and why do they shut off when dad hits the brakes and not come on at all on my truck.?????

Go to the Auto Parts house and get you an adapter with LED
test lights - that way you can see if the trouble is on the truck
side or the trailer side....

I have heck getting the round adapter to socket properly and some
WD 40 and thin emory board filing will usually get things lined out...

When the LEDS work the lights should too....

sound likes a ground issue to me...

idk what to tell you i have the same kinda issue.. my trailer running light wont work but the brake and blinkers work so idk..

i'd go with giga on this one

I bought the tester that plugs right into the truck. I hit the brakes the led comes on hit the blinkers they work as well. Hoos the trailer back up and same thing left side is dead. Even bough a new adapter and my truck is brand new so their isnt any corrosion on the plug or the adapter

It is definitly a short or ground on the trailer, has nothing to do with your truck. Trace all the wires out

Ground.
Is the white wire on the trailer plug hooked up? If not run a jumper to the truck and check it out. Rusted hitches and rusty balls do weird things.

That was going to be my next comment

Alright Thanks guys. I'm going to try and run a jumper and see if that does it. It is strange how it has power to the lights but they dont turn on. I'll keep ya posted if I get it fixed.

Get you a solid ground and you'll be good to go. The brake wires rest at ground. When you hit the brakes, the wire goes to 12v. That's why the lights work until you hit the brake...

Anytime 12vdc shit aint makin sense- its the ground

trailer lights are constant pain in the a**.... you my friend have a ground problem somewhere.

Thanks again guys. I know I hate trailer lights. They work when ya plug em it and by the time ya hit the landing they are off. I guess anything electrical you pull in and outta water a few hundred times a year can have some issues.

just a suggestion! my buddies trailer was doing the same thing. and it ended up being the eliment in the left light. i would take the light of the trailer and shake it, if you hear something rattleling in the light its time to get a new one cause it shorting its self out when you hit the brakes. if you cant hear anything in the light element then take your battery charger and attach it to your trailer wires and crank it to 60 amp jump start. then look along the frame or in the tube for smoke! if it smokes thats where your short is!

Just for shits and giggles check the fuse box control center in your truck. I had problems a while back in my Silverado 1500. Left side and right side trailer lights are on a separate fuse as well as tail lights. If one of the fuses is burnt or going bad, it does weird things to your trailer lights.

Trace out all your wires again for a short on the trailer. I had that problem before as will. One small piece was chafed making contact with the trailer and it would ground everything out when you hit the brake lights. Its hard to find but that may be your problem as well.

I had this happe to mine i hooked up a ground to both sides of the ligts with one ground to one side and a jumper going across to the other bolt and they work fine now.

contact cleaner any electric supply house will have it maybe even home depot in the electrical department spray plug on the trailer and truck and do so about three times letting it sit 5 min in between then as said before the way your trailer makes ground is also threw the trailer ball brush it good with wire brush if rusted if not splice in a jusmper to the white wire scrap metal good and screw straight into the couplier of the trailer

It's a ground. Especially if you have power to the lights like you are suppost to. Clean where your lights bolt up or run a third wire to each side of the back of the trailer and you'll have it hooked.

Are sure da light bulbs are not burnt out or dat da contacts on da bulbs are not coroded?

OK so I finally got a chance to check out the trailer turned out to be a very easy fix. I have a trailer with a swing away tongue so you can get it in the garage easier. Turns out when it came from factory the wires were piched inside where it swings away. I have never used the swing away attachment and the trailer is only like a year old. So i opened it up found 3 wires almost fuzed together. So I seperated them reconnected and soddered them back together and walla trailer lights are working great. Thanks again for the help It made it pretty easy to track down