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orggardn's avatar
orggardn
Explorer
May 16, 2016

Running lights not working - how to troubleshoot?

I had an odd problem when I connected the 7 pin connector to my F150. Usually, I turn my headlights in full "on" mode, so when I'm behind the truck and the connector seats - I see the running lights come on.

On Friday, I tried and no running lights. Must have fiddled with it for 20 minutes, with a sickening feeling that the trip may have to be cancelled. I finally thought, I'll try the turn signals....sure enough turn signals and brake lights worked. No running lights, no tail lights. I checked the dash and the trailer sensor for brakes connected was functioning properly. Since we would travel both directions in the daylight, we went on, without incident.

Now that I'm back, I need to get that resolved, but don't know where to start. In the truck? In the trailer? At the connector? My trailer wiring IQ is pretty low..... so suggestions in newbie terms please.

Thanks.

**NOTE: item of note. I had an electric jack installed since the last time we went out. Is there perhaps a connection there?
  • Check for a trailer connector fuse. It could be located in fuse block under the hood or under the dash. Check the owner's manual.
  • I did take a small file and hit the trailer side connectors with it to get a clean(er) base. I did not do the truck side.

    You know..... seems like I was having to wriggle it a bit a while back to get it work. Sounds like a good cleaning is in order.

    Westend - are you saying your truck has a separate fuse for just the lights? and brakes and signals is on another? If it's a single fuse, then I don't think it's that as I had turn signals and brakes, just no running and tail lights.

    Thanks guys.....
  • Awhile back I had to `drill' out the sockets on my connector due to corrosion. Obviously using a small dia drill soas not to make the opening larger. But it's the only thing I could think of that would clean out the hole.
    I now spray Corrosion X on the contacts when I think of it. Guess I better do that today!
  • Sometimes I have to wiggle my 7pin connector to get everything to work. When was the last time you cleaned the contacts in the plug and the receptacle?
  • Your tail lights and markers are powered by the truck through the towing umbilical cord. A quick check of the truck's socket pins for power is where I would start.

    FWIW, my Ford F250 has a separate fuse for trailer light circuit. The owner's manual should help locate it's position in the main fuse panel.