Trailer Still Messed Up

I posted the other day that I ripped my Trailer plug off my trailer. Im still having issues with it and haven't got it straightened out. When I hot brakes on truck or controller in truck I have power at three poles in the plug. two our the same signals that light up when you turn the turn signal on the other is the third to the right. Its the White wire same wire that goes to my trailer brakes. My question is that I didn't see any wires in the plugs that our grounds? Should there be one in the plug connected to the center pole? Where should I start? Everything but brakes on the trailer our working. However it keeps popping fuses if I hit brakes or controller. Any help is appreciated.

You say every thing is working but brakes and you blow fuse when you hit brakes. To me it sounds like you have a short in the braking system.

I missed your original post. Six pin or seven flat blade RV plug, or seven pin round semi tractor plug? You can Google trailer plug diagrams for the proper arrangement you need. IF your plugs are wired to 'code' you can go from there. If not, get your back dirty and start tracing every inch of the wiring. A couple of wires could have pulled loose in a light and are touching each other, or ground. I always joke only half-heartedly that a loose bare wire WILL touch bare metal where an insulated wire won't. A lot of used trailers are wired with any color wire the 'electrician' happened to have on hand. Jim

Yes there should be a ground,when you step on brakes you say three pins light up? one should be for the brakes and the other two are for brake lights, what ever conector you have they are marked either on the cover or where you put wire in as to what terminal is what. You will have to figure what is what on the trailer it may not nessarily be color coded

One pole on the outside is larger, that should be the ground and should have the white wire attached, although sometimes they use black for ground. Yellow and green are turn, yellow for yellow line side, green for green grass side. Brown is clearance lites. The other outside wire is usually blue and is the brakes, but some use the center one for brakes. Some wire cables have red and black with red for brakes and black for ground. If you look at the plug the posts will be labled with the first letter of the wire color. Of course if you wires are a different color or someone botched then you are on your own. That should be confusing enough for you.

I got to thinking about this, and I have another suggestion. Someday put a whole day aside to remove all of the old wiring and replace it with a properly color coded new harness. You troubles will be over for a couple of years at least, depending if you shed the trailer and how much you use it. I get carried away with having everything straight and proper to the point where others just walk away and come back when I'm done, so this might sound like overkill, but at least you will have a base to start on. Won't help your imediate problem, unless you have time to re-wire now, but it's something to think about.

Google is your friend when you want to find the proper color coding for the plug you have. Why the wiring gods had to change the color coding in the newer style 7 pin RV plug from what it has been for decades is beyond me but I still don't have it memorized.Good luck. Jim

I've used this link to fix several trailers. The colours often aren't wired right if an owner has been into it but your can figure it out based on the connectors.

Blowing the controller fuse means you have either a short to ground or a low resistance connection to ground on the hot brake lead.
Trailer Wiring diagram for all types of connectors

Popping fuses when you power up the brakes? You've messed up more than the plug you've done something to the brakes circuit that has made a short. My guess is when you pulled the plug the brake wire was on the side of the loom that got pulled across or into something and now you are the proud owner of a short circuit. Follow you brake wires and look for bare spots, don't stop after the first one, where the wire goes through the backing plate is popular location.

I use a 2 amp battery charger. power the wires on the trailer to see which wire does what. If one wire is shorted the charger will keep tripping the breaker and the wire will get hot enough you can feel it but still won't get hot enougn to cause damage. follow the warm wire til you find the short. the wire past where the short is will not be warm. Wire the plug to match the truck.

Regardless of wire colour, looking at the 7 flat pin socket on the truck which is usually mounted so the flap lifts up, the prong at 11 o'clock is your tail/clearance lights, 9 o'clock is left turn/brake light, 7 o'clock is ground, 5 o'clock is power for electric brakes, 3 o'clock is right turn/brake light, 1 o'clock is 12V for charging breakaway battery or interior lights on trailer, center pin is backup lights.

Trailer plug is the mirror image of truck plug

In my opinion, EVERY trailer should have its wiring ripped out completely any time something doesn't work right, or once a year, whichever is sooner.

I realize that some people buy quality trailers new from the factory, maintain them properly, and never take them off the pavement. They also either park them for the winter, or live where that isn't an issue.

However, I have never seen or worked on those trailers, all my experience has been with stuff that should be loaded up with scrap iron and left at the scrapyard after it goes across the scales. The owners don't want to hear about replacing anything, but will spend their life savings on Scotchlocks, electrical tape and other Band-Aids, also the labor to tinker on it and the defective equipment tickets.

Most of the problems I see are from poor grounds, poor grounds, and poor grounds. Then there is physical damage, corrosion, corrosion, and corrosion. After that comes did-it-myself, and in a hurry. And going back to cheap owners, whatever lights, wire, and connectors they could get at Walmart, or take off some other piece of junk they own.

I finished this and realized that it is more of a rant than any kind of useful advice for the original poster. It does sound as if there is still hidden damage from the original problem, and a complete replacement of the wiring may be a real short cut in terms of labor and frustration.

Make sure you didn't cross the brake wire with the ground wire some where would be easiest thing to check then start tracing for a short or rewire.


I use a test light and back of plugs to wire all my trailers. And all have been used when I got then seems to work. Haven't rewired anything more then a couple spots where wire nuts and scotch locks were used yes have seen wire nuts used on trailers that see salt and road grim. Some people I tell yah