How do you find a trailer light short?

It looks like I have a short in my trailer lights. When I got done fishing tonight and hooked up the trailer lights, the running lights went out. Blew the fuse in the engine. Gave the lights a quick once over and didn’t see a problem. Through a new fuse in and it blew again right away. Drove home with my fingers crossed and no running lights. Brake lights and turn signals still work fine.

I had the same thing happen a year ago or so and it turned out that the light bar on the back of the trailer under the keel was full of water causing it to short out.

My question is, how do you find a short if it isn’t something obvious like a light full of water? If I keep putting fuses in, they just blow before I have a chance to try and track anything down. At least its only the running lights so I can still go fishing as long as I get home before dark.

Any help would be appreciated. I know absolutely nothing about trailer lights or electricity, but I don’t believe it is a ground issue since it is blowing fuses. If it matters, all the lights are LED lights.

I would start by looking at any place the wires go thru the frame for frayed wire also pull the side lights and make sure they’er hooked up to main wire harness we got lucky when my sons trailer was blowing fuse occationaly,when I noticed light was out and there was a bare male end pulled out of light hitting frame internally this is a tough find without a little luck.or disconnect back lights and recheck for short try to eliminate things that could contribute to short,to save fuses get a volt/ohm meter to check continueity on tail lights to ground. good luck

Stan

hey just noticed 100th post a long ways from some!

They can be anywhere! Rubbed wire, loose grommet or water as you stated. Best is to work backwards. My guess is you have a LED pig tail that has come loose and the ground peg of the pigtail is touchng the frame and grounding out. Check all the connections making sure they are plugged in. Most likely you will find a unplugged one. If all look good then unplug them all and try again. If the fuse does not blow you have a light some how gounding out if the fuse still blows with all the lights unhoooked you have a bare wire rubbing somewhere. Best place to start looking for that is anywhere the wires come out of the frame.

Looks like Bassn is a faster typer!

Well if brake and turn signal work then those wires ( green and yellow) seem ok and it would be the brown color common tail light wire that is bad. You can use a battery charger to check lights. Apply power to each individual lug on the connector and see what happens. No fuses that way to blow. Had a friend just do this on his boat. Brown wire was frayed in the tongue channel. The splices at the Y portion back were good when we check there.

A couple years ago I had head aches with the same problem, I finally just changed the wireing harness. I had several places on the harness that vibration rubbed through the insulation inside of the frame. Thirty dollars for a new harness solved all of my problems and it only took about an hour and a half.

All the above is good info…and if it’s old wire, changing it out isn’t a bad idea either.

I found a direct short to ground a few years ago by using a VOM and my FW.

Switch the VOM to check for resistance x1. Connect the leads to the ground wire and the brown in this case. Now, have your FW watch the meter and start wiggling wires. When the offending wire is moved off the frame, you have narrowed down the area of the short. Once you know the general area, start looking at the wire where it’s rubbing on the frame ect. With a little luck, you know the spot in 15 minutes.

This is done with the trailer unplugged from the tow btw.

Or you could take it to a Marine Dealer along Hwy 61, pay them $70 and tell you the problem is the fuse in your truck. Dang I have a long memory when it comes to getting screwed.

Exactly what he said but check the plug first to make sure its the trailer. I had a dumb mistake this year I had a livewell pump that wasnt working this year and checked fuses thought they were all ok and replaced the pump. New one didnt work either. Make sure your checking the right fuse…… Do all newer boat trailers have a seprate white(ground) for each side and my middle 3 have their own set of white and brown to the tongue?

Arghh, trailer light problems!

I just had the same exact problem as you and found, mostly for my own sanity, the best way to correct the problem was pay a shop $120 to do it for me. I figured I’d get over the price long before I’d get over not being able to tow my boat up for the opener.

Trailer lights can cause more fits than a cheating wife!
(I think…)

I went out at lunch and picked up voltmeter / continuity checker thingamajiggy. Now if I can figure out how to use it, I’ll be in business. Thanks for all the suggestions. I’m sure by trying everything suggested, I’ll eventually end up with working lights again.