Possible trailer hitch wiring issue

I use my XJ a lot to tow a small-ish trailer (4 ft. x 8 ft), mostly in lieu of buying a truck to haul dirt, wood, stuff that won't fit in the cab, etc.



The trailer lights work great for braking and turn signals, but the trailer lights don't light up when the headlights are turned on. The brakes and turn signals still work fine with the headlights on, but they don't light up like they should so people can see the trailer in the dark. Make sense? Because of this, I avoid towing it at night as trailer lights are required at night where I live. Sometimes I can't avoid it.



The trailer is super basic and the only lights in question are the two brake lights on the rear. It is wired with a 4-way flat plug and the night lights work flawlessly on another vehicle that has a 4-way flat plug on its hitch. My XJ has a round 7-way, so I have to use an adapter between my XJ's hitch plug and the trailer connector. Anyone else run into a similar issue? I've confirmed that another vehicle that has the same 7-way connector is unable to get the lights to work either.



Since this is pretty much the only trailer I ever tow, I'm tempted to replace the 7-way connector to a 4-way flat connector. Thoughts?

Bad 7-way to 4-way adapter? If you have a meter, you can check that you have voltage at the blade on the 7-way on the vehicle, and confirm that your adapter is wired correctly. The brown wire on the 4-pin should be the running lights. If you have voltage, it could be a poor connection too.

It sounds like your "converter" may have gone bad.

RCP Phx said:

It sounds like your "converter" may have gone bad.

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I too thought that was a possibility. We also tried a known good adapter/converter on two vehicles with the same result.

I'm not talking about the adapter plug, I'm talking about the "wiring converter" you should have somewhere behind the driver rear interior panel.

My park lamp pin corroded to the point that it quit making good contact. I ended up buying a new 7 pin socket.

As others have said, I would look into the adapter being bad as well.