Trailer Lights Dilemma

gogittum

I've got a dandy going here that has me shaking my head and laughing/crying.

Last week I bought an older 12 ft MirroCraft tin boat with 15 hp outboard, sitting on an older trailer.  Basically sound and can be used as is....almost...but there are a few things I've been working on.  As expected, lights on trailer were u/s, so tossed 'em and bought a cheap kit online that has both tail lights, both marker lights and about 25 ft of 4 strand wire with 4 pole plugs.

Late yesterday, I re-wired the trailer and mounted the lights.  Lights wouldn't come on, so figured with all the rust and layers of paint I wasn't getting a good ground - the usual cause.

I drilled and tapped holes by each light and ran separate grounds to each one, then checked ground from car to car plug and showed power at all 3 terminals with a 12V test light.  Plugged in trailer and no lights.  

I clipped the ground alligator clip to my new main ground on trailer, then poked the needle tip thru the insulation on each brown (tail light) wire and the yellow and green turn signal wires.....this is on the trailer side about a foot downstream of the plugs at hitch.

All showed power at the test light.....but still no lights on trailer - on the far end of the same wires.  Went down to each light individually, clipped to ground and probed thru the insulation.  Nothing on any of them.  HTH can this be ??  I've wired a lot of trailers.....and lots of other stuff, too, and when you have an unbroken wire with power at one end, then there will be power at the other end, too, right ??  Hah. 

I walked away from it for a while, then went back with a clear head and fresh viewpoint.  No change.  I don't know WTH to think.  Can't be the bulbs (these are cheapie non-LED) cause no power is showing where wires enter lights but power is showing at other end of wires.   Aaaarrggh ! ! !

Terry Ravenscraft

Sounds like it has to be in the plug connection

gogittum

I'll take a couple of pictures in the morning.  I don't think I'm explaining clearly.

The Cat's Eye

My job in the USAF was an electronic trouble shooter.  i did not do repair work but just found problems and then called up one of the various repair units depending on the type of problem I found. (Micro Wave, crypto, teletype, telephone, German landline, IBM computers, and one more i can't think of). Several decades later at my house,  AT&T could not figure out why i could not get reliable computer service and told me the problem was inside my house;s wiring and not their problem. I finally took a strong 8 X magnifier to inspect the copper wires where a tech had used an insulation stripper and found hairline cracks in the copper strands. The tech standing behind me told me they were not allowed to use wire strippers, but i told him someone did and cracked the copper strands just enough to cause problems. When the offending wire tip was cut off and reconnected the problem that had stumped several AT&T technicians was solved. These cracks did not show up in continuity testing, but were causing problems as time went on, no doubt to an increase in resistance.

 So repeat the connections and use minimum pressure while stripping off the insulation. Or replace the entire wire.

gogittum

I hear ya, but this is fine gauge, extra flexible multi-strand and I did use the correct notch in the stripper.  No strands cut off.  Crimp connectors are as tight as a two handed mash on forged steel crimper can make them  It's the standard 4 strand flat wire that comes in the trailer light kits - 2 brown, 1 yellow, 1 green, bonded together side by side in a flat band with a white ground wire coming for about 2 feet off the plug on trailer side.  

A wire broken inside the insulation is unlikely with this stuff but possible.  4 wires all broken from the factory inside the insulation.....uh.....??

Haha......it's gotta be something simple, but I've brain far.t.ed myself into mental paralysis.  Like I said above - I'll take a couple of pics in the morning.  Maybe a fresh look will help, too.

conchydong

So from what I am understanding is that somewhere you are losing continuity in the wire somewhere between the flat plug and the lights? Could happen on one but like you said not on all four. Send that chit back to China and get another light kit before you go crazy.

Alex from GA

Where are you clipping the ground when you test @ the lights?  When I check for trailer lights I connect my battery charger or another battery directly to the trailer plug.  Still think the ground @ the lights aren't making contact.  Run a separate wire to the white @ the plug to each light temporarily to check.

The Cat's Eye

i have seen defective wires like you describe,,,,rare but possible. One rat or mouse chewing on the flat wire could let in moisture and you might not even see the punctures. Or the wire was stretched in production and the copper strands were broken. I would use marine wire and dump the flat four wire.

Terry Ravenscraft

You explained it clear ..sorry i overlooked a foot down from the plugs !

gogittum

conchydong said:

So from what I am understanding is that somewhere you are losing continuity in the wire somewhere between the flat plug and the lights? Could happen on one but like you said not on all four. Send that chit back to China and get another light kit before you go crazy.

Just about has to be the ground but I don't see how.  When I take the pictures I'll explain.

Not a long journey for me on the other.  😢

Alex from GA

This suggestion is what I used on my last trailer light install.  On each trailer light there are 3 wires, I cut the white one short put a ring terminal on it and, using metal screws with drill points and 1/4" hex heads, screwed them to the trailer then covered the heads with silicone.  I did the same thing with the plug end on the trailer tongue.

snookaffinity

I am a little confused (normal for me). Have yo tried running a ground wire from the white wire on the plug to the white ground wire on the light?

pottydoc

Run a dedicated ground wire down both sides of the trailer, and hook to the white wire on the lights. Hook both of them to the white wire on the trailer plug. I’ll bet you’ll have lights then. Almost all trailer lights issues on boats are caused by bad grounds. Running ground wires from the vehicles ground to the lights almost always fixes it, and it remains fixed. 

gogittum

Thanks for all the thoughts, guys.....all good ones.  A guy on another forum came up with it and I slap my silly, senile head.  The trailer is a tilt trailer (forgot that) and the bushings are insulating the front of it from the rear.  dohhh

MGD

Get 2 - 3 wire extension cords that are long enough to go from plug to lights.
Cut off the ends.
Use those to wire your trailer lights. 
Relying on the trailer as a ground is asking for trouble.

pottydoc

MGD said:

Get 2 - 3 wire extension cords that are long enough to go from plug to lights.
Cut off the ends.
Use those to wire your trailer lights. 
Relying on the trailer as a ground is asking for trouble.

That’s the way I do mine. After they been required that way, they’re usually good to go for years. 

gogittum

As threatened, I ran a separate wire past the pivot on the trailer and the lights work like brand new.  Thanks all for the thoughts.

Alex from GA

Smear some silicone sealer on the **** you made in the wires to check the voltage.

Alex from GA

OK holes.

deckape

Is the trailer attached to truck/car.?  Can not be grounded if not on ball , as ground in plug is to ground on car / truck. Ball makes a better ground

pottydoc

The ball absolutely does NOT make a better ground than running a dedicated ground wire to both sides, hooking it to the white wire of the plug, and then plugging that in to the female connection on the vehicle. The lights will work fine that way even if the trailer is not attached to the vehicle. You could actually remove the lights and harness from the trailer, lay it out in the yard, and they would work. 

Klinger

pottydoc said:

The ball absolutely does NOT make a better ground than running a dedicated ground wire to both sides, hooking it to the white wire of the plug, and then plugging that in to the female connection on the vehicle. The lights will work fine that way even if the trailer is not attached to the vehicle. You could actually remove the lights and harness from the trailer, lay it out in the yard, and they would work. 

This!! ^