Trailer running lights acting up.. Help please :(

I got a 06 TRD sport with the tow packet. there is a problem with my wires on the truck i cant seem to figure out. My running lights will only work sometimes. Brake and signals I have no problem. is the two yellow markers in the front, side markers on top of the tires, the rear lights on the top and the rear tail light on the left that don't work. right rear tail light will work just fine. I had replaced the 7 pin connector wire harness with a new OEM and it worked for half a day. I had the trailer 4 pin connector replaced with a new one, problem continued. I hooked up a new wire harness from the tail lights to see if it would work, problem continued. all the fuses are good, I have not had any of them get blown. I had another trailer connected when it was acting up just to make sure it was not the trailer that had a wire problem, the 2nd trailer did the same thing. when ever the running lights would be turned on, only the right side back light would work, none of the other lights in the trailer would work. Keep in mind this problem is not all the time. some times they work and some times they don't. I had a voltmeter hook up to the pins to make sure it was getting current, it had between 12v and low 13v constant. I was told it could be a ground issue in the truck been that it does it with other trailers also but so far i have not found the problem.

If anyone has an Idea of something else I can try or where to look for the problem please help.

thank you

 

If you had 12V to 13 V at the plug pins and the lights didn't work you have a ground problem.

 

Check the ground at the lights

 

My 7 pin OEM plug is a piece of crap. I have to move the trailer connector around to make sure all lights work. Fortunately I have a 7 pin plug with indicator lights on it.

 

CURT 58270 7-Pin RV Blade Trailer Wiring Towing Vehicle Socket Tester, Black

http://www.amazon.com/CURT-58270-12V-Connector-Tester/dp/B001EOWQY4

 

Check your ground, and NO, the ball is not a good ground, you need a ground wire. Next wiggle the crap out of your 7 pin to 4 pin adapter, those are junk and don't last real long. Yours may be making poor connection.

I always had trouble with the standard lights and the way that the wires just push in, they are always giving me problems. I bit the bullet on my utility trailer and my boat trailer last year and went all LED, I'd did so on my boat too. Well worth the money ..... eBay is your friend for those lights.

If you stay with standard lights, I clean the bulb terminals real good and apply dialectric grease.

 

yeah my trailer already got LED tail lights only the regular running lights are not LED. how about the fact that I connected an aftermarket harness to the tail lights of the truck and it still does the same thing? I did buy a new 7 to 4 connector just to eliminate the possibility + with the direct harness there is no need to use the adapter.

is there a way I can add an additional ground to the trailer or the connectors itself?

Thank you again for the feedback