When I plug up a boat or camper trailer, I get the exact opposite reaction that I should from the lights on the trailer.

For example, break lights are on then go off when I press the break.

Needless to say, it's very frustrating because I feel it's a grounding issue but I am not sure where to start. Should I replace the wiring harness? That seemed pretty easy to do tonight, but it appears I am going to have to remove the spare tire to do that.



Any advice or help is greatly appreciated.

 

Sounds like the stop lamp and running lamp wires are mixed up...

 

I hadn't thought of that. How hard (or easy) is that to correct?

 

Do you have a 4 way flat or a 7 pin connector on your trailer?

Also what year model?

FordMasterTech

 

FordMasterTech

It appears to be 4-pin.

It's a 1997 F-150, 4.6, auto, swb

While screwing with it, I accidentally shorted it out, so I found the fuse in the box under the hood that I need to replace. But after I do that, I am still going to be stuck with old problem.

I also noticed last night that turning my headlights or parking lights on has the same affect.

Oh, and the lights stay on the trailer stay on, even if the truck is not running or break peddle pressed.

I need to try to fix this tomorrow because I am supposed to pick up a camper about 7 hours away.

Your advice is greatly appreciated!

 

Did the plug come wired from the factory or is it a plug that has been installed? Who installed it? Was it a splice-in plug or did wires have to be tapped?

If it was installed at the foctory, I doubt that its mis-installed, but if some other place/person installed it, the potential for mis-installation is great.

Have you tested it other than on one particular trailer... maybe the trailer is mis-wired?

WalMart has a little tester block that plugs into the plug and has little LEDs on it that you can look at while activating certain lights and it will verify proper wiring of the plug.

 

1997 and up ford trucks have Alum. bolts in the hitch to the frame and they do not ground good put a strap on the bolts and that will take care of it.

 

And the saga continues...

I decided to replace the entire factory 3 flat wiring & no one (Wal Mart, Autozone, Napa nor TSC) stocked it...they had it for pre 97 f150s.

I am going to try to re-ground it...lowered spare & checked everything out to make sure it was connected...wiring harness is grounded to the of the truck.

Thanks for your replies & any more suggestions i will go out right now to the garage & try!

I am heading to Atlanta tomorrow to get my new camper, so I will have to live with break lights on while i drive, then go off when I press the breaks...If I haven't figured this out by Tuesday, I will have to turn it over to my friend @ the Ford dealership & he will have it fixed in 2 mins and make feel real DUMB!!

 

Just disconnected ground from frame and (as expected) lights did not work @ all. Cleaned spot where ground makes connection to the frame, tightened & still have same prob.

So now I am leaning away from a grounding prob and more towards something more serious.

 

After having experts look @ the prob & consulting with the pros, I have for now (and maybe forever) given up on fixing the prob with the factory installed trailer lighting & just installed an entire new setup by tapping into my rear breaks.

It works perfectly so I may just live with it like this, as much as I hate to not use what was intended.

But I got the trailer home (400 miles) and now prepping it for a week of vacation in the Great Smoky Mtns.

Thanks guys for your help!

 

I wouldn't recommend tapping into your wiring harness to "fix" your problem. The reason all F-150's come with a flat 4 trailer hookup (even without the trailer package) is to avoid people doing just that. Newer vehicles with all of their computer controls are just to sensitive to the way things are hooked up electrically to have folks messing with important wiring like that. You may have fixed one problem only to create a more serious - and maybe costly - one down the road.

Oh by the way, tapping into a wiring harness with Scotch Locks and other quick tap methods usually leads to all sorts of problems with bad (corroded) contacts down the road. I refuse to use them on anything I install. I'd have a professional look into your problem and fix it right. Good luck!