How to debug / fix this wiring short?

[someguyinnorthcarolina]

I have been off the portal for about 7 years due to family caregiver issues, during which time my 2001 Coleman Bayside sat neglected in the back yard. We had bought it around 2012 and then "life happened" and we never even got to use it.

This week, with the help of a friend we opened it up. Surprisingly, after some cleanup, it's in good usable shape. My #1 first problem to fix is that the lights don't work. I honestly don't remember if they ever did. I do know the only thing I did when I bought the trailer was to put a new 7 pin wiring plug and harness on, and hook it up via a junction box to the trailer's wiring harness. But I don't remember if it ever worked when I did this.

I've verified all 7 pins are working right coming out of the TV.
I've verified that all 7 pins coming into the terminal junction box on via the new plug are good.

But on the wiring going into the trailer from there, I've got a problem. I don't have a color-coded list for the 2001 Coleman Bayside, but I'm pretty sure the colors are this (someone please correct me if I'm wrong):

White - ground
Black - 12V accessory hot
Red - left
Brown - right
Green - running
Blue - brake
Yellow - reverse

I have checked where the white wire grounds to the frame, and that still looks solid.
I have inspected the back of the trailer where the wires come through the subfloor to the rear panel, and see no cracks, etc

But using my ohmmeter, I have continuity between the green, brown, red, blue, and white wires. That should not be.

I guess in the worst-case scenario I can just start running new wires.
And I'd really like to avoid having to pull off the rear panel at this time just to get the lights working.

I'm hoping to get the trailer lights working first and then make sure the brakes work before making a decision about how much to invest (sweat and time and money) in some of the other repairs (cleaning up and grizzly-gripping the ABS panels and roof, replacing the seals, and replacing some rotted subfloor).

Thanks,

Carl

 

[Raycfe]

THe very first thing I would do is connect a ground wire from the trailer plug to the frame of the trailer at the front tongue area.
Mice like to eat the wiring in the frame on the streetside front corner. Also take apart the ground connection on the rear cross member. It may look tight, but the well nut could be causing a bad connection.

 

[neighbormike]

"Typically" trailer wires are:
White - ground
Brown- Tail/ running
Yellow- Left
Green- Right
Blue- Brake

 

[eoleson1]

I pulled the owners manual for your camper from our resources page. It lists the exterior wiring colors. Your list matches theirs except they dont list a yellow wire or reverse lights. The seventh wire in their list is black with a red tracer as another 12v aux wire.

One thing you need to keep in mind is the tow vehicle wiring will be quite different:
Yellow - Left turn and stop
Green - Right turn and stop
Brown - Running lights
White - Ground
Blue - Brakes
Black - 12v aux
Purple (or whatever color they use not listed above) - Reverse

To start, pull the bulbs and check continuity through them to make sure they're good.

Then I would get a battery and two jumper leads. Put a fuse in the lead you'll use for positive. Connect the negative jumper to the white wire, then test the red, yellow, and brown wires with the positive lead. See what if anything comes on.

 

[jckele]

Your continuity tester is showing a short but really you are reading the resistance of the lamps, brake coils and what ever load may be on the aux line. Changing the scale on your meter to a x1 or very low scale will result in proper readings. Better still, remove the lamps and retest those lines, your short will be gone ( except the brake & aux power ). If so, put the lamps back in and try powering with a battery as suggested. The frame ground may look great but take it apart and clean it. Everything on the trailer, powered by the vehicle, relys on this wire. Strange things happen with a bad ground as power back feeds through wrong circuits.

 

[WrkrBee]

But using my ohmmeter, I have continuity between the green, brown, red, blue, and white wires.

Just to clarify- you have continuity between the green and brown wires? green and red wires? green and blue wires?

 

[someguyinnorthcarolina]

Yes, I have "n-way" continuity between all these wires and the white wire.

And yes, I'll follow the guidance y'all have offered. Thanks much. I need to be patient to debug this because my panic side wants to just give up on this pup.

 

[eoleson1]

Yes, I have "n-way" continuity between all these wires and the white wire.

As long as the circuits are complete, you will have continuity between all of those wires. You need to start breaking the circuits apart to get meaningful continuity.

 

[jckele]

Yes, I have "n-way" continuity between all these wires and the white wire.

You really don't have continuity! You are probably not on the correct scale of your ohm meter. The meter is giving you a correct indication for the scale it is on, but it is misleading information. Have a look at the picture in the link,

http://secretsonearth.blogspot.com/2019/06/meter-reading.html

It is my ohm meter connected across a small 12v light bulb. Starting from the left side, the meter indicates 0.00 but I'm on the 20M ohm scale. The wrong scale for measuring a light bulb. The next pictures moving to the left are the 2M ohm scale, 200K, 20K, and the second last is the 2K. Finally a reading, .007 but there is a multiplier of 1000 ( K ) so it is reading 7 ohms! Going to the lowest ohm scale produces a more accurate reading of 7.6 ohms. It's no longer indicated as a short but a small resistance. That scale on my meter is the 0 - 200 ohm. The most suitable for checking this type of circuit.

Take one of your trailer lamps and try it yourself. Attach from the outer bayonet base to one of the end pins with your meter on the lowest scale and see what you get. Your brake circuit my even give a lower reading as they are just coils of wire.

I hope it makes sense, and redo the ground wire regardless of how good it looks.

 

[WrkrBee]

Have you taken a 12v battery and powered the pins in the camper plug, one at a time, to see if the lights work?

 

[someguyinnorthcarolina]

Have you taken a 12v battery and powered the pins in the camper plug, one at a time, to see if the lights work?

No but I will. You folks are giving me hope on this rig

 

[someguyinnorthcarolina]

Some progress tonight before it got too dark and the insects got too annoying. I pulled all the light covers and cleaned the grunge out, and tested all the bulbs for continuity.

As predicted the ground wire was a nasty rusty connection. I couldn't get it to unscrew, so I snipped the wire and will mount it to a nearby hole. I put a wire brush on the drill and cleaned it down to bare metal. That's about the time I called it a night.

We're in for several days of rain, so I may not get more progress on this for awhile. I need a barn...

 

[someguyinnorthcarolina]

An update (as there was a window of non-monsoon time)

I made a good clean new ground wire connection, and pulled all the bulbs on the trailer. Testing continuity between the wiring leads now with the new ground connection, but no bulbs in, I had still had continuity between ground and electric brakes and ground and running lights.

When I disconnected the newly-attached ground wire and re-tested the leads, I did not have continuity to the electric brakes but I still did have continuity to the running lights.

Then the rain began to come back so I high-tailed it back inside.

My thoughts, and I eagerly welcome yours:

• Continuity between the unattached ground wire and the running lights suggests that maybe I forgot to pull a running light bulb or I have a running light fixture that is bad
• Continuity between the attached ground wire and the electric brakes suggests that it's just coming across the electromagnetic

My #1 goal is the running lights - next opportunity I will double-check I did not leave a bulb in.
Assuming I didn't leave in a bulb, what's next to look at for the lights. And any guidance on the brakes also accepted.

Thanks!

Carl

 

[jckele]

I made a good clean new ground wire connection, and pulled all the bulbs on the trailer. Testing continuity between the wiring leads now with the new ground connection, but no bulbs in, I had still had continuity between ground and electric brakes and ground and running lights.

Progress, good to hear. Best to keep the ground wire connected. You will always show some resistance on the brake circuit. As you said it is the electromagnet coils. That's a good thing otherwise your brakes wouldn't work. If you look under the trailer behind the brake plates you will probably find 1 brake wire grounded to the frame rather than run to the front of the trailer. That might explain the loss of continuity with the white disconnected.

As for the running lights, did you remove all the lamps? There will probably be at least 6 as all the marker lights are part of the running light circuit.

Stay dry!

 

[someguyinnorthcarolina]

I neglected to remove the bulb for the license plate. I'm not sure how to remove it, but that would explain the running light continuity.

 

[someguyinnorthcarolina]

Some success and a lot of a surprise (and then it started raining again)

With the ground secured and bulbs back in, I hooked up to the TV and was dismayed to find nothing working (or so I thought). I had the emergency blinkers on when I was walking back to the truck and saw a small pulsing glow from one of the lights. I popped all the light covers back off (lesson learned: never put these on until you are done!), and all the bulbs are working, just very, very faintly.

Well - almost all. It seems that the left and right turn signals are both coming on regardless of which way I signal. I used a trouble light to test at the TV connection, and the TV is only sending signal on the side requested.

Then the rain came, which left me wondering two things I didn't have time to figure out:

• what voltage level is showing up at the trailer junction box connection for things like the running lights? I wonder if I've got a big voltage drop causing the bulbs to be so faint (note that for the running lights I went ahead and ordered LED replacement 194 bulbs. Hope that is as straight-forward as I make it out to be)
• What is going on with right and left?

I'm getting there - and pondering an LED upgrade to the brake/turn lights when this is resolved, but my understanding is there's more to it than just a bulb swap.

Brake controller didn't show talking to any brakes, but I'll ignore debugging that until lights are working.

 

[someguyinnorthcarolina]

I should have dug deeper; E-Trailer suggests it's still a poor ground: https://www.etrailer.com/question-13551.html

 

[jckele]

I should have dug deeper; E-Trailer suggests it's still a poor ground

Sorta sounds like it. Could very well be on the vehicle side. You could try jumping frame to frame with a piece of wire or a jumper cable if you have a set. Poor grounds always create weird results.

 

[someguyinnorthcarolina]

I'm going to try using a jumper cable from truck frame to trailer frame to establish ground and see what happens (when I have time and a reprieve from the rain)

 

[someguyinnorthcarolina]

THe very first thing I would do is connect a ground wire from the trailer plug to the frame of the trailer at the front tongue area.
Mice like to eat the wiring in the frame on the streetside front corner. Also take apart the ground connection on the rear cross member. It may look tight, but the well nut could be causing a bad connection.

I wanted to give credit to you, that I should have done this first.