Floridaguy80

Just got my new trailer and realized that the wiring harness on the hitch is not working like it should.
Whenever I turn on my parking lights in the truck the parking lights on the trailer light up. Whenever I apply my brakes, put either turn signal on or put my emergency flashers on the lights on the trailer do not correspond to what the truck is doing. I bought one of those little trailer harness test kit adapter for a few bucks that has four LEDs on there. The only Led that lights up is the one for the parking lights.
It is a factory hitch with the tow package so the harness is factory as well

What could be the issue here? Ford won't be able to get my vehicle in for about a week to look at it

Floridaguy80

Okay I just put a voltmeter up to the wiring harness, both the seven pin and four pin on the back of the truck. The right and left turn signals and brake lights are all dead the only thing that gives me 13 V is the running lights.
I checked the fuses in the engine compartment according to the manual The fuses are in location 37, 38, 39, and 73. They all appear to be intact and seated properly into the distribution box.

Facio

There should be some connections for the trailer harness by the rear of the truck, just follow the wires from the harness. At times these connections let moisture in and corrode over time, happened to me with no left side turn signal or brake light, finding the problem and installed a new piece of wire and good as new. Good luck.

Feathermerchant

Also I think there are relays between the trailer tow fuses and the wiring. So the signals, brakes drive the relays and not the actual trailer lights. Probably 2 relays.

Floridaguy80

How so you check for a bad relay?

Feathermerchant

Pull it and test it. 12V on the coil and it should click as it closes the contacts.
If you can find out which relays, you can use your test meter to check the circuit integrity from the relay socket to the trailer connector.

benchwarmer4203

What year is your truck? Is this the first time you've ever tried to use the 4 or 7 pin receiver?

Floridaguy80

2013 screw eco. I bought the truck used to weeks ago but it only had 6000 miles on it.
Yes this is the first time I'm using the trailer 4 pin adapter.

benchwarmer4203

Are you checking the turn signal voltage with the truck running, or at least with the key in the "on" position?

Feathermerchant

You can also check them without the truck running if you turn on the emergency flashers.