Car trailer lights??
 

2004 F350 diesel/2007 open car trailer.

Seven pin wiring connector.

I've got emergency flashers, turn signals and brake lights,
but no running lights on the trailer.

Am I missing a bad fuse on the truck? #6 on the fuse block
is for the trailer wiring and it is a good 20 amp fuse.
#37 is for trailer parking lights and that fuse is good too.

Open to comments and opinions.

Re: Car trailer lights??
 

Look for a second fuse for the trailer running lights under the hood. Not a Ford but my Suburban had the same issue and replacing the underhood fuse was all it took.

Re: Car trailer lights??
 

Philip -

Look for a brown wire coming out of the 7-pin trailer plug. If you've got voltage there, somewhere on the brown wire is a/are splice(s) into the tail and running lights on the trailer. If not, it'll be on the truck side of the connector.

Hope this helps!

Lew

Re: Car trailer lights??
 

Had the same problem with an enclosed trailer. Everything worked except the running lights. Turned out it was a short in the trailer wiring.

Re: Car trailer lights??
 

Is there power at the brown wire when the lights are on? They most likely have a relay somewhere to insulate the regular circuit.

Re: Car trailer lights??
 

Phil
Just tape flashlights to the trailer fenders. I've been doing it for years.
Just remember to turn them on. But if you don't like that there is a relay/fuse under the hood.
Mike

Re: Car trailer lights??
 

Dealing with the same thing right now... Replaced all trailer lights with LED's back in February, and everything was perfect until a month ago. Started blowing the trailer parking lamps fuse in the truck. I found a section where it looked like the wires may have rubbed inside a metal channel, so I insulated them, problem fixed. ...for about a week. Replaced that section of wiring, problem fixed. ...for about five minutes ...PER run time! That I *really* don't get. Trailer lights work, then going down the road, they'll go out, then blink on if you go over a bump (for awhile, then they quit completely). Jiggle what you will, nothing. Next day, turn on the switch, and you've got lights again, without touching anything. I could understand something overheating over time and blowing a fuse if something was shorting, but how do they just stop working w/o blowing the fuse?

Same deal, though... all the other lights work. It's just a parking lamp issue. Been turning the parking lights on in the race car if it's dark on the way home.

Thinking I'm going to have to do a complete re-wire from scratch to solve this one. Hateful!

Re: Car trailer lights??
 

Michael
Don't know if this will help but I had lights thet were on and off so I ran a seperate ground wire from truck to trailer with a single plug and the problem was solved. Quick, easy and cheap to try.

Re: Car trailer lights??
 

Happy 4TH of July to all on the board, sad to see that my
house is the only one on my street flying an american flag.

Thank you all for the informative responses.

I have checked and I have power for the running lights at
the back of the truck (seven pin plug).

Tomorrow I'll try adding a temp external ground wire from
the truck to the trailer and see if that makes any difference.
If not then I will be in the same boat as Mr Beard and need
to rewire some on the trailer.

Mike Graham, as much as I like your suggestion about the
flash lights I have to believe that is a Arizona only type fix,
not something that would go over very well here in LA LA
land. Of course the CHP does not seem to see my rig when
I'm out on the road. Too busy chasing down those bright
colored mini box's flying past me on the freeway.