Hi folks im new here so be gentle. I have a 2010 f150 with the trailer package. I have power on the 4 prong connector but when I plug the trailer in I have no lights whatsoever, no running lights, no break lights and no signal lights. The issue is not with the trailer as 5 different trailers have been tried and all have the same issue. All fuses are tested and good. Also the trailer had no issues on my previous vehicle or on my friends GM vehicle where everything works fine. The issue I have is I have power on all pins of the 4 prong connector with no trailer plug inserted. If there is power on all the pins, I have tested with a vom and all pins work for running lights and turn signals yet when I plug the trailer in nothing. I am at a total loss as to where to begin as if there is power from the ground pin to all other pins the lights should work. Any and all advice would be helpful as I have never had so much trouble figuring something like this out. It is most definitely a truck issue as like I said everything works fine on my buddys GM truck. HELP

 

Did you confirm your ground? Are the pins dirty or corroded?

 

Is your ball really rusty?

 

^^lol^^ he said rusty ball. It's a ground issue

 

Some trailers use the ball as a ground. IMO total pain. Sand off the ball rust

 

posts are clean, trailer hitch is the slide in type and the receiver is rusty but the holder is new with paint on it, I can grind that off and neversieze it before installing it. Also I thought the white wire was a ground so in theory shoudnt it work without the trailer being hooked to the truck as both plugs have a ground to them, just asking. Also my trailer is an aluminum trailer so rust is not an issue as all bolts are stainless.

 

Does the 4 and 7 pin plugs share the same ground wire ? Plug a 4 to 7 pin adapter in the 4 pin and see if you get lights... might help lead in one direction or another.

Thad said, I know very little about electricity, but I tow a lot

Good luck !

 

Maybe my reading comprehension has taken a dump, but did you say you had power on your ground? That shouldn't be.

Take a jumper from your trailer tongue, and ground it to a spot on the truck. That will eliminate the ground pin in your 4 way. Then go from there.

 

To clarify I have 14 volts from the ground ( white wire) and the brown wire with running lights on. With signals on 14 volts between the white wire and the yellow wire for left and 14 volts between the white wire and green wire for right turn signals. These voltages were taken directly at the 4 prong connector on the truck without the trailer hooked up. On the trailer I have continuity from the white wire of the plug to the trailer body as checked by a VOM and continuity from the truck white wire to the body of the truck. This is why I am so confused as everything says with continuity to ground and power to the hot wires it should work. My next step is to plug trailer in and put pins in all the wires to see if the voltage is being lost when plugged it. I will also try to run a separate ground wire from the truck to the trailer body to eliminate any grounding issues. I am no plug when it comes to electricity but this issue has even me stumped. Thanks for all the advice I greatly appreciate it. I am also thinking that it is a grounding issue as the wiring is correct coming from both connectors.

 

I've had problems with the 4 ways myself. On one truck, I gave up, and bought a 7 to 4 pin adapter. It worked, and now I just leave it on that trailers pigtail. I've found those flat 4 pin connectors leave a lot to be desired. They almost seem like corrosion magnets.
Please post what you find out, but my money is on the ground pins for the truck/trailer connection. Those things seem to turn green just by looking at them.