Maybe A simple Solution, But..

[squirrel hunter]

Thanks again, if it was a ground wire problem wouldn't Ilose all of the lights instead of just the running lights?

I will definitely check for nicks in the brown wire and do the plug-and jiggle exercise.
Moose, you said your problem was a loose wire on the side light but that means that light must not have been working, my lights all work fine until I blow the fuse.

[Jerry Blake]

Sound to me (like others have mentioned) that you have a short somewhere from the trailer wiring to frame. If you can't find any bad places in the wiring that is exposed you may have to pull the wiring out of the frame. Like Tom said though you would expect to find it somewhere that is exposed. If you have to pull the wiring out just securely tie and tape some heavy cord to one end and pull it in as you pull the wire out. Then you'll have it there to pull the wiring back in.

Check all your fixtures too for pinched or frayed wiring or problems where the bulb screws in. If you are using any kind of grease in the sockets be sure it is non-conductive or current can pass through the grease from the bulb contact (hot) to the base (ground) and cause an overloaded circuit.

Good luck - electrical problems can be a real pain, especially whey it works when it wants to - like when you’re trying to troubleshoot it.

[Moose1am]

I told you about me fixing my trailer lights and all the blown 25 amp fuses I had to contend with on my last trip down to the Teezur tournament. I fixed my trailer along I 24 with semi's driving by me as I lay on my back under the trailer with a small flashlight and had to remove my eyeglasses so that I could see up close. Even with Bifocals I can't see things that are only a few inches away. And being under the boat I could not get far enough away to see the wiring and such without taking the glasses off.

You are lucky you can fix your tailer at home, hopefully. I had not choice but to fix my on the side of the road. Luckily I had my tool man and it had a screwdriver and pliers and a sharp knife to help me do the job. I had to fix mine as the fuse the kept blowing out turn the inside lights on my dash board off and also prevented my brake lights and emergency flashers in my truck from working. I blew about three fuses along the highway before I finally was forced to pull over to the side of the road and finally fix the wiring.

When you are towing the trailer the WIND blows the wiring around and that is when the wire's ends can make contact with the metal of the trailer. That or vibration makes the wire rub on the metal and causes the short to happen.

Intermittent troubles are hard to trace. I doubt if the wiring inside the channels is bad. check where it goes in and out the channels, any exposed wiring. Plug trailor into vehicle and jiggle wires at different locations to see if you can isolate a given area that my cause the problem. I usually dont do this, but without a meter, it is an option. It seems the fuse is protecting the wiring from any damage. Check your wiring to see if it is limber. If you are drawing too much current, the wires tend to stiffen. Also look for discoloration in the brown wire, like a darker brown area in the same wire.

[KARL]

Squirrel Hunter--If you replace the fuse and the lights work fine the whole trip and the fuse is blown next time you hook up....then sounds like problem is in truck pigtail where it hooks into wiring on truck--IF I follow correctly the fuse doesn't blow until you re-hook trailer...have you checked your fuse after trip is over to ensure this...or check fuse periodicly without trailer hooked up.
also are just trailer running lights out or any lights on truck effected??? also check what else blown fuse on truck controls ie..radio,lighter etc..in my work as mechanic i've seen some weird electrical problems..also have you changed any bulbs recently..may have replaced with wrong type..had similar problem on my trailer not to long ago..relaced all quick splices with hard solder connections and clean small spot on trailer to bare metal to get good ground..
problem went away...feel free to pm me and I'll help all I can..If need be I'll give you my phone# and talk you thru on phone...Houston we have a problem..

[Cane Pole]

Karl has a good point here. If u have replaced any bulbs, check them. Wrong type could draw too much current. Also, repeating Karl, check truck before and after. I also agree with Karl on the splicing. Solder, then heat shrink. If you have to splice a wire, use a gel filled splice. They (gel filled splices) will prevent moisture from entering the splice and causing corrosion, and eventually failure. Splices are no-no for me. Karl, I teach electronics, but u are right on. Heed Karl's advice SH.

[tarfu]

howdy; you can buy a new wire harness at any u-haul store. maybe 10-15 bucks. at the tounge of the trailer tie the new harness on to the old harness. go to the rear of the trailer tounge. pull it all through except for the plug and enough to connect to tow vehical. then, simply work your way around the trailer ONE LIGHT AT A TIME. should only take about 1 to 1 1/2 hours. you know your wires are good and right then. lol tarfu.

[Jerry Blake]

Hey Tom:

Have you seen the new (well to me anyway) crimp connectors that have the heat shrink covering right on them? The insulating covering is longer than normal - extends beyond the metal crimp part by about a half-inch or so - and you just heat it up like regular heat shrink after you've done the crimping. I think they are made by 3M - a bit expensive but very convenient.

Do you think they would work about as well as a soldered and heat shrink covered splice?

[fish21759]

I had a problem like that and it drove me nuts . I checked wires and made sure it was grounded good but still had a problem . I finnally took the lens off the taillight and found moisture inside the waterproof bulb capsule . Not much was in there just a couple of drops but it must have been enough . I bought a new waterproof bulb capsule and have not had a problem since .

Kevin ><)))*>

[RLR]

I had the same thing happen to me and replaced all the wires and lights on my old trailer. Well a week later it happened again and it was then I figured out what was blowing the fuse. The strap that I used to go across the middle of my boat to secure it to my trailer was pinching the wire where the hooks went under the trailer.

[KARL]

I agree about your take on splices, Cane Pole, also about the use of heat shrink...If I have something that gets wet alot or stays wet not only will I heat shrink it but wrap with electrical tape and then cover with liquid electrial tape--maybe overkill---but ounce of prevention--etc...the liquid tape is some real good stuff can seal almost anything...don't ever have to worry about shrink drying out and cracking..thanks for the back-up, but if you teach electronics I will have to defer to you...Oh Grand Poobah..ha ha ha :D