Travel Trailer Tail Light/Running Light Issue

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swhydro

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Chatham Ontario
Hi folks, new here.
Have a 1987 Fleetwood Terry resort travel trailer that I'm having problems with the exterior lights. All the running lights on the front half of the trailer work, but nothing on the back half works, no running/marker lights or even brake, turn signals. If I apply 12v power directly to either tail light, both tail lights and all the marker lights work. I already know that everything is in working order where the truck plug/cord meets the camper cord junction underneath the tongue of the trailer. Then, the green, red and brown wires start to run down the center of the trailer, in between the black plastic belly and floor frame, towards the rear of the trailer. I'm only able to trace that back as far as I can reach.
My question is, would anyone know if those wires would continue right down the center of the trailer, overtop the holding tank, or will they shoot off to one side (or maybe both sides) somewhere down the line? Each tail light has two green wires connected to it plus the turn signal wire (2 green in each)

I found where it looks like mice have chewed a hole through the plastic belly, right over top of the black holding tank. I can only assume that they have chewed through all 3 wires somewhere under there..... :(

Any information would be greatly appreciated!
 

JayArr

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Mice usually only chew the insulation, they rarely chew the copper. This happens on newer units more often than older because older units used a plastic/poly type insualtion and then some genius decided it would be more environmentally friendly is they made wiring inulation out of organic material. The mice seem to like this switch. LOL

My Terry is a 91 and all of the rear wiring for the tail lights seemed to come down from the top so there is a chance that somewhere along the line the wire's head up to the ceiling and head back from there.

Have you thought about getting a tracer tool?

 

John From Detroit

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Generally exterior lighting follows the frame rails.. Key word "Generally" there are no guaranges.
i've used the Harbor Freight Cable Tracker.. Worked great.
 

Kirk

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f I apply 12v power directly to either tail light, both tail lights and all the marker lights work.
Do you mean that applying power to one light turns them all on? If so the problem is probably the ground side of the lights and they are back-feeding to reach return. Do you have a good ohm meter as you can use that to check for continuity of the various wires, by using a jumper lead.
 

Ex-Calif

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If I apply 12v power directly to either tail light, both tail lights and all the marker lights work.
This indicates the power feed is bad not the ground.

TBH - If faced with this and I could not find the open in the wire, I would patch in new wires and remove/cut away as much of the old stuff as possible. Sometimes, as others have said the wires go through a frame rail or other fixed feature of the RV.
 

swhydro

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Joined
May 16, 2022
Posts
6
Location
Chatham Ontario
Mice usually only chew the insulation, they rarely chew the copper. This happens on newer units more often than older because older units used a plastic/poly type insualtion and then some genius decided it would be more environmentally friendly is they made wiring inulation out of organic material. The mice seem to like this switch. LOL

My Terry is a 91 and all of the rear wiring for the tail lights seemed to come down from the top so there is a chance that somewhere along the line the wire's head up to the ceiling and head back from there.

Have you thought about getting a tracer tool?

Just wanted to double check everything before I post again. So, driver side of trailer has 2 green, 1 red and 2 white coming to the fixture. The passenger side has 2 green, 1 brown and 2 white coming to the fixture. If I plug it in the truck, ground my test light to the trailer (known good ground source) doesn't matter what lights I turn on in the truck, I get no power in any of the rear trailer wires with my test light. If I apply 12v direct to either fixture, the lights work. The top marker lights work if 12v applied to either side. Would this not mean a mouse would have had to chew threw 3 wires in order for this to happen? If that is in fact the issue. I even put new fixtures on, which we were planning on doing anyway.
So let's jump ahead and say I want to run new wiring to the back. How would I go about this? Sorry, very new to the travel trailer world. How would I go about routing the wires and getting them to the holes in the back of the trailer?
I can give a cable tracker a try, only one store in my area sells them. But more and more it's starting to sound like it might be easier/quicker to run new wiring....

Thanks for the replies everyone
 

Mark_K5LXP

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I agree with your observation, it's not likely three wires are chewed through or otherwise broken. It's implied that since nothing works, you have a bad ground. Could be in the trailer, or the tow vehicle. My first test would be to verify your fixture ground (should be the white wire) is grounded to the trailer frame, then run a temporary ground wire from the trailer frame to the vehicle frame and try it that way. Another test would be to check continuity from the light assemblies up to the 7-pin or whatever connector your trailer has, there may be a break somewhere at or near the connector.

Mark B.
Albuquerque, NM
 

swhydro

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Chatham Ontario
Ok, making some progress folks. I ran a wire from the back of the trailer to the front. Connected it to green wires of one fixture (all wires disconnected from lights) then did a continuity test from that wire to the trailer plug. Doesn't matter if my continuity test wire is connected to the green, brown or red, I get continuity to the same 3 terminals at the plug.
So, by this I am going to assume that they have chewed the 3 wires in a manner that they are touching together somewhere? I haven't purchased the cable tracker as of yet, would it help determine where this spot is? Or am I wrong and that's not what's causing this?

Thanks again! :)
 

Kirk

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After making my living doing electrical service work for 40 years, one thing that it taught me was to troubleshoot one problem at a time. It doesn't hurt to remember that they could be interconnected but to do more than guess requires simplification. I suggest you start with the diagram below.
7-Way-RV-Diagram.jpg

Using this as a guide, start to trace 1 wire at a time.
 

Mark_K5LXP

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Did you remove the bulbs before making your continuity measurement? Otherwise the filaments will show a short across their respective connections.

Mark B.
Albuquerque, NM
 

Ex-Calif

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Ok, making some progress folks. I ran a wire from the back of the trailer to the front. Connected it to green wires of one fixture (all wires disconnected from lights) then did a continuity test from that wire to the trailer plug. Doesn't matter if my continuity test wire is connected to the green, brown or red, I get continuity to the same 3 terminals at the plug.
So, by this I am going to assume that they have chewed the 3 wires in a manner that they are touching together somewhere? I haven't purchased the cable tracker as of yet, would it help determine where this spot is? Or am I wrong and that's not what's causing this?

Thanks again! :)

It still sounds like a shorted circuit involving 3 wires.

Using the Ohms function test between the green and red, the other green and red and the green to green. If the meter shows no resistance then you pretty much have a short between the wires.

However...

If I apply 12v direct to either fixture, the lights work.

This indicates that you could also have an open wire between the trailer plug and the fixture you are referencing.

It could be that the critters not only chewed 3 wires to short them together but may also have chewed them into an "open" circuit condition.

Did you remove the bulbs before making your continuity measurement? Otherwise the filaments will show a short across their respective connections.

Mark B.
Albuquerque, NM

Good call. It's important to be able to think about where the current will run. If in fact 3 wires are shorted together you can hook the black meter cable to ground and if you flash any wire it will show continuity to ground minus system and bulb resistance. In other words you will measure the bulb resistance.

I still don't think there is a short to ground as when 12V is applied the lights come on.

At this point if you want to investigate further you need to disconnect the wires at the "fixture" end as well as the lights end so that each wire is not connected to anything.

Then flash between the suspect wires (green to red to brown etc.) to confirm they are shorted together. You can also flash each one to ground to confirm they are not grounded and the last test is from the trailer plug to the back of the rig to confirm there is also an open circuit.

TBH - I am a little confused about your terminology - I am not sure what you mean by "fixture" Is there a junction box at the front of the rig that all these wires start from?

A fixture is generally the Light fixture assembly itself which will contain one or more bulbs depending on what fixture it is.
 

swhydro

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May 16, 2022
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Location
Chatham Ontario
It still sounds like a shorted circuit involving 3 wires.

Using the Ohms function test between the green and red, the other green and red and the green to green. If the meter shows no resistance then you pretty much have a short between the wires.

However...



This indicates that you could also have an open wire between the trailer plug and the fixture you are referencing.

It could be that the critters not only chewed 3 wires to short them together but may also have chewed them into an "open" circuit condition.



Good call. It's important to be able to think about where the current will run. If in fact 3 wires are shorted together you can hook the black meter cable to ground and if you flash any wire it will show continuity to ground minus system and bulb resistance. In other words you will measure the bulb resistance.

I still don't think there is a short to ground as when 12V is applied the lights come on.

At this point if you want to investigate further you need to disconnect the wires at the "fixture" end as well as the lights end so that each wire is not connected to anything.

Then flash between the suspect wires (green to red to brown etc.) to confirm they are shorted together. You can also flash each one to ground to confirm they are not grounded and the last test is from the trailer plug to the back of the rig to confirm there is also an open circuit.

TBH - I am a little confused about your terminology - I am not sure what you mean by "fixture" Is there a junction box at the front of the rig that all these wires start from?

A fixture is generally the Light fixture assembly itself which will contain one or more bulbs depending on what fixture it is.
I'll try some of these other things you mention. When I mentioned "fixture" earlier, I was referencing the lights at the rear of the trailer:
Connected it to green wires of one fixture (all wires disconnected from lights)
But yes, there is that black junction box under the tongue of the trailer where all wires meet.
 
Last edited:

Mark_K5LXP

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Just as a general comment, when things are not behaving as you expect then isolating components will eliminate variables and make the subsections easier to verify. So not sure what you mean by "disconnnected", meaning each wire of the lamp assemblies was open? That will definitely isolate the assemblies, is there a trailer brake unit involved? Or any other gadget connected to run/brake/reverse like maybe a camera or aux power point? Just offering suggestions.

A looooong time ago I had electrical weirdness going on with my motorcycle. When I turned the headlight on the brake light would come on, and if the headlight was off and I put on the brake, the headlight would come on. I could not for the life of me figure out how those two lines could cross. I eventually did find it, the brake light bulb filament had broken and fallen on top of the running light filament, and effectively those two circuits became shorted together. The filaments still worked so the bulb was not immediately suspected. After that little exercise the *first* thing I do is remove the bulbs, not only because of a one in a million bulb fault but vehicle light fixtures/sockets are subject to water and mechanical damage that may be evident upon inspection. Upshot of my post here is never assume anything, even the most "obvious" thing that can't be wrong, can be.

Mark B.
Albuquerque, NM
 

JayArr

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The running lights on the sides of the trailer are in parallel with the running lights in the rear tailight assemblies.

If you didn't remove ALL of the lights you may still be chasing a ghost that doesn't exist.
 

swhydro

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May 16, 2022
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Location
Chatham Ontario
Sorry folks, I'm currently waiting spinal surgery so there may be gaps in between times that I'm physically able to proceed with this.

So, with both light fixtures removed from the back of the trailer and ALL wires tested separately, this is what I get:

-- ALL 4 green wires give continuity to the running lights, left turn and right turn slots of the trailer plug.
-- Red wire from left turn, NO continuity to any slot on plug.
-- Brown wire from right turn, also NO continuity to any slot on plug.

Purchased the cable tracker and have managed to get as far as learning the wires from the right light fixture, run along the back of the camper (about half way up) towards the left light fixture. From the left fixture, they run up towards the roof and then run down the left wall of the camper towards the front.
I'm planning on working with the tracker some more, but it's not omitting enough sound through the camper wall, to pinpoint where there may be a break. It works fine when you are close to the tracker connection, but once you get a little ways away, it really fades.

Will update when I'm able, and find something more.....

Thanks
 

tlmgcamp

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Jul 16, 2016
Posts
99
It might be helpful to install wire loom on any wires that you can get at. That might slow the critters down
 

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