this is my first post here, i hope its in the right spot. I just bought a 2004 f150 SuperCrew. I plan on pulling my boat with it, and when i went to hook up the trailer lights i noticed that who ever owned it before me had cut off the original factory round trailer plug-in on the truck, and instlled a different one that is now broken and needs to be replaced. The original flat four hook up is still there. My question is .. i plan on replacing the broken round plug with a new one again but when i try to use both the factory 4 and and current round one i cant get any power through the yellow wire that runs the left brake and blinker. i have checked all the other wires with a tester and they all work but the yellow one. I have looked around and can't see any places where the wire could be broken or anything because its still wraped in the factors plastic.im stuck and hope i can get some help.. THANKS in advance...

 

Check the fuses yet ?

Sticky at the top of the Hauling and Towing forum:
https://www.f150online.com/forums/sh...d.php?t=184757

Left is F42, 10A

THis sticky also has part numbers for the 7 pin round harness ( from the trailer tow connector to the connector along the frame rail, ~ where the spare tire is, driver's side. Easiest to drop the spare tire to see it.

good luck, let us know what happens

 

THANKS A MILLION!!!!!!!!! i got it to work now.. It was the fuse, i must have over looked it 10 times in the book. i didnt know there were different fuses for each side. thanks again..

 

You notice I forgot to put a red block around it in the sticky also It happens

great it is working now.

 

If you have problems with fuses, pick up some breakers instead. I got mine at NAPA, but the angle by the pins is different from the fuses. The fuses have a narrow taper where the breakers are more of a wedge shape. Took a nice sharp wood chisel and shaved a little off the fuse surround and they stay in place real nice. You have to trim the strip inside the cover as well.

 

Fuses aren't the problem, wiring and overloading is the problem. Try instead to add separate relays if you have too much load. cut the load off the fuses.

 

That is what the factory trailer tow adapter does. This might have been a short to ground blowing, vs. an overload protection blowing of the fuses.

 

grounding out is a part of "wiring and overloading"

 

True, but adding a relay isn't going to do anything for this. I was pointing out that the trailer tow adapters already have a separate fuse, and relay for them.

Adding another relay to the relay that is run from the truck's lighting circuits, isn't going to help with a short to ground problem.