I bought one of the replacement 7-pin & 4-pin connector adapters for my truck,
the OEM connector had a lot of corrosion.

when I plugged in the new connectors, before it was mounted up, it worked just fine.
It comes with a metal bracket that can be screwed to the rear of a stock truck.
but, my truck has Ranch Hand bumpers...

when I had my new winch installed up front, I asked the Fab Shop to install the new trailer wiring harness. They had to remove the connectors from the Metal Bracket and somehow, get them thru the 3/16ths thick Ranch Hand bumper plate.

I don't think they ever tested it to verify all is good.

when I hooked up to the trailer's 7-pin cord, the Left Turn and Marker Lights are the only things that work.

at first, I thought a fuse was blown, then in a rare moment of insight, got to wondering if the 4-pin connector is good?

Low and behold, the 4-pin connector is good.....
so, what did the Fab Shop do to break the 7-pin wiring?

Now I have to take them out and look at the splice where the harness is made up.

just to be safe, I ordered up a new one, it looks like this:
this one is $49

a Ford OEM version is $165 made in Mexico, not China....
should I buy that instead? gag ... cough...

 

Check the spring loaded contacts are tight.

 

I have a 7-pin tester that I use for a quick test



Here it is showing TM or Running Lights - Trailer Marker they call it


and here the LT blinks, but none of the other pins work.
I have a Lisle Test Lamp probe to see if the other pins are live, they aren't.

 

Move up the chain. See if there is an issue with the interconnect between the truck wire harness and the 7 pin connector wiring.

 

that is my next step,
it is hard to get my big hands on the connector, can't get the release to come apart.

it has a Ranch Hand bumper and huge Tow Hitch 2"x2" tube in the way...

just barely get a hand through the open space, to touch the connector.

need to get it up on car jacks, so I can work with it better.

wish I had a Lift....