Trailer light wiring

dlogvine

Master Chief Petty Officer
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May 4, 2015
Messages
832
Tried to put new rear lights with the old wiring. It worked for the old lights at least for the ones that were functional. However when I put new lights, no power. Tried to clean up the ground wire and even cut the old wire close to the tongue. Strange thing, when I hooked up the power wires of the test light to the cut out portion of the wires and grounded it on the trailer, it worked in places close to the ground but when I tried to ground it further down the trailer, poof, stopped working. Any ideas why? Tomorrow I'll try to thread new harness and see how that will work. Thx
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,306
most likely bad ground. with every used trailer I get, I buy trailer wiring in a 100' spool and run a dedicated ground down each frame rail and use epoxy lined heatshrink at every splice joint.
 

savetexomabeaches

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Jul 4, 2013
Messages
420
New lights == new wires. Trailer wiring isn't that expensive and its always good to just replace if old and crusty. But it sounds like bad crusty grounds. Also, never use those snap connectors, they are the worst. Get heat shrink butt connectors
 

gm280

Supreme Mariner
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Jun 26, 2011
Messages
14,585
I have to agree with the above suggestions. Replace the old wires with new wires and run a dedicated ground wire to each light. That way you know for sure you have a good ground. Using the trailer as the ground is never a good idea. Too many possibilities for the ground to get corrosion at the lights themselves that way. The lights are only as good as you install them. JMHO
 

riverkeg

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Jul 31, 2009
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Dedicated grounds are great but I don't believe they are the only way. Grounding through the trailer has been a tried and true method for many years and can be very reliable when done correctly. The 2 big things to get right are ensuring the wire to frame connection is clean and protected (I paint over them when done), and that you have a ground jumper when dealing with a tongue that is bolted to the trailer frame. One benefit over dedicated grounds is less wires to pull when installing a new harness. I do agree with soldered connections covered with dielectric grease and heat shrink tubing.
 

aburke120

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Jun 27, 2011
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183
I agree with riverkeg dedicated trailer grounds, and clean connections are a must. I just did a trailer yesterday using the wires from another trailer. Checked all the wires for bare spots, cleaned up all the grounds for the harness and the light mounts. Everything works fine.
 

dlogvine

Master Chief Petty Officer
Joined
May 4, 2015
Messages
832
The trailer is a little rusty at spots but seems like the problem is with the ground connection. Also the rear lights are mounted on the removable fixtures, which also provide some problems for clean ground. I'll just drop the dedicated ground wire and see if I can reuse the old power wires. This trailer, 1994 Escort, has a real pain in the ass little 1/2" holes through which the wires to the marker lights have to be threaded. Just a big pain in the neck.
 

Tinman2809

Cadet
Joined
Aug 23, 2017
Messages
16
I have the same problem..i spliced the connections for now...used liquid electric tape but once fall hits I will be doing some rust repair, painting the trailer and adding new led lights...working with those little holes suck...try using an electrician snake to help you guys the wires or use the old wires as a guide
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,585
The trailer is a little rusty at spots but seems like the problem is with the ground connection. Also the rear lights are mounted on the removable fixtures, which also provide some problems for clean ground. I'll just drop the dedicated ground wire and see if I can reuse the old power wires. This trailer, 1994 Escort, has a real pain in the *** little 1/2" holes through which the wires to the marker lights have to be threaded. Just a big pain in the neck.

Some times you can use a vacuum cleaner (shop vac) to suck a string attached to a larger cotton ball through small openings. It really depends on if there are other holes to bleed off the vacuum suction. Takes a good strong string, tie it to a larger cotton ball and suck it through the hole/channel to where you want it to go. Then tie the string to the wire(s) and pull them through. I will say this, any place where the wire comes through, you need to either use a grommet or some type material to keep the wire from chaffing and shorting to the trailer. JMHO
 

aburke120

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Jun 27, 2011
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"you need to either use a grommet or some type material to keep the wire from chaffing and shorting to the trailer."

You aren't kidding there, I just fought a floating ground on a boat trailer, then removed all the wiring and put in new. The old stuff had so many scrapes with bare wire from pulling it through the same small holes you're talking about. use grommets as stated above, or hang it from something.
 

dlogvine

Master Chief Petty Officer
Joined
May 4, 2015
Messages
832
I will use a fishing line to pull the new wire through the holes. The only small holes that could cause a problem are the marker light connection holes. I might just remove the fender markers completely, the rear lights would be an easily accessible places and the snake would work fine.
 

aburke120

Petty Officer 2nd Class
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Jun 27, 2011
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183
If the frame of your trailer is square like mine was you'll have trouble getting that fishing line from one end to the other, I used a #6 wire to get through the whole frame, but you don't need a wire that big I used it because it was here.
 

dlogvine

Master Chief Petty Officer
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May 4, 2015
Messages
832
I have a metal line, specifically designed to fish the wires, so with the rectangular crosscut it will be pretty easy task, unless there is something blocking the passage. I'll make pictures and post them online.
 

dlogvine

Master Chief Petty Officer
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May 4, 2015
Messages
832
No Title

Today after a several hours of working in this heat, I finished with the trailer wiring. Such a pain in the neck... Checked every connection before went to the next wire, had to get some better connectors and more heat shrink tubing. Decided to go with designated ground wire. The main problem was that the wiring was going inside of the trailer frame with very small (about1/2") holes through which the wire was supposed to be fished. But at the end everything works fine and all connections sealed and insulated. Fishline was extremely helpful. Also I made some hooks from the wiper blade inserts and was able to pick up the wires through the frame with that tool.
 

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dlogvine

Master Chief Petty Officer
Joined
May 4, 2015
Messages
832
Finally, every light on the trailer is working, I also bought a couple amber marker lights and replaced old broken ones. Now every light is working, trailer is repainted, fenders straightened. Time to start working on the boat itself.
 
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