I have a 2000 f150 4x4 ext cab that i have not pulled a trailer with in a few years, so i hooked up a trailer the other day and noticed the female plug on the truck was in rough shape and i had no light except for the right turn signal, so i changed the plug and same thing, so i did some searching on this forum and found out where the harness for the trailer and back of truck light are above the spare tire and i have no power to that harness for the trailer except for right turn, but have power to all the back of truck light and they work. I even checked the wires infront of the harness and same thing, so i don't think the problem is this harness. My question is, Is their another harness somewhere infront of this one for the trailer wires that i should be looking for and if so where would it be located... thanks in advance for any help you guy and gals can offer...
Jim...

 

Did you try checking the fuses for the trailer tow adapter ?

If you do not have power at this conenctor :


My thought would be the fuse is bad.

 

WOW... Do i ever feel like a tool now, I never even thought that the trailer wire would be on their own fuses, looked through the owners manual and sure enough they are, and every one was blown except for the right turn signal, Go figure... Thanks for the heads up SSCULLY...

 

Glad it was an easy fix, and thank you for posing back with your solution. This is missing too often in threads.

Some of the trailer tow circuits also have a relay on them, for future reference.

 

thank you SSCULLY. I have an 03 f150 and I replaced my trailer wiring harness and had no lights at the back of the truck. I started browsing the web for info and finally got to your diagram that showed the coupler above the spare tire. I checked it out and it was unplugged. I must have pulled on the harness and unplugged it. I think the locking tabs are broken so I'll have to zip-tie it together tomorrow. Now I can drive my truck to work in the morning instead of riding my bike. its a little too cold at 4:30 to be flying down the road on the harley

 

Thanks SSCULLY. I was under the impression that the tow lights were all one circuit so having turn signals and no running lights made me think that I was going to be chasing a bad wire. Instead I replaced one fuse. This is why I love these forums. Thanks again