Tail lights on when disconnected from TV

Toby13

Hi all,
We just picked up our 2017 T@G from winter storage. We hooked up the battery, plugged in to shore power, and noticed that our right hand tail lights stays lit up even though the trailer is disconnected from our TV. Any thoughts or suggestions on how to fix this? Is it possible we hooked up our battery incorrectly?

We are very very very new to trailers and electrical (though I've read through the electrical 101 posted in another discussion, I still don't quite follow it all), so any simple and detailed explanation would be greatly appreciated.

BBsGarage

Not to sound insulting, but are you sure it is on and its not the sun or some other light source reflecting in the lens? Iv'e been fooled by that before. Having said that it could also be some sort of short causing it to activate. check under the fender and look for any frayed wires to start.

Toby13

100% certain it's not the sun, as we noticed it at night and it is just one side and not the other.

I'll have a look at the fender this evening.

BBsGarage

Sounds like something is shorting then, follow the wires as far as you can from the light to where it enters the trailer. After that it may require removal of the power panel to look further. Does it stay lit when you turn the battery kill switch off?

Toby13

I'll have to do some poking around when I get home tonight. I'll check if it stays on when the battery kill switch is turned off. Thanks for the starting points!

Michigan_Mike

I would revisit the battery wiring as it sounds like something is amiss here. Another point I will make here is that LED lights are very sensitive and I've seen where lights do come on when a small amount of voltage is present on a curcuit. On my T@B I know that the bathroom light comes on when I turn the battery on/off switch on after it's been sitting.

I would inspect the wiring at the battery and ensure that you have things hooked up properly as it sounds like you have voltage leaking across a wire somehow and creating the condition. A pinched wiring harness could be the issue, bad ground wire, etc. I'd look at any wiring beneath the trailer too if you can't resolve it at the battery posts and try hooking the trailer up to the tow vehicle, try your turn signals and 4-way flashers and see what happens that way and go from there. If there is a serious shirt curcuit issue a fuse will normally blow, but stranger things have happened.

Let us know what you find and what you believe the problem is.

Verna

@Toby13, what make and model of tow vehicle do you have?

I haven’t found the similar discussion on the T@B forum yet, but it seems that some tow vehicles need a relay installed in the wiring harness. I know the relay part comes from etrailer so I’ll keep on searching.

Toby13

Hi @Verna ,

This is happening when the trailer is not connected to the TV, (hasn't been connected to the TV for several days). Would that still be something to look into?

Either way, it's a 2014 Subaru Forester.

Verna

@Toby13 all I have found so far is that there are separate wiring harnesses for vehicles with LED or incandescent lights.....but that should not be your problem as you reminded me it was for days after being disconnected from the tow vehicle.

As Michigan_Mike mentioned, there is a wiring problem. For the lights to remain lit on the T@G, there must be power and ground completing the circuit. So, you do need to check your wiring. Rodents may have chewed the wiring while in storage, so it is possible only the rear lights wiring is touching ground, i.e. the frame or a ground wire or any other piece of metal. There is a recent wiring diagram posted that shows which wire you need to check, but please check all wiring for any damage.

LuckyJ

Inside the a frame, you have an electric junction box. The short could be coming from that location. The space is very small and dirt could have got in there.

And while you are in there, I would apply a coat of dialectric grease on the connectors. It would help protect the wires for the futur.

And if nothing id foumd in the box, you could start by disconecting one wire at the time to see if you can locate the culprite, but you keep the trailer light connected.

Toby13

Last night I tried to isolate where the power was coming from. I managed to determine it was coming from the shore power. However, after I unplugged the shore power, then plugged it back in, the light went out on its own.

I looked at the wiring from the light all the way to the junction box, none of it seems to be chewed or frayed. Seeing as the light went out on its own, I'm going to leave it for now, I don't want to go poking around if I don't need to. But if it happens again, I may need to open up the junction box. Thanks for all your suggestions!

WilliamA

Toby,
On its face, this interesting (to we mechanics anyway) problem probably sounds like a nightmarish scenario to figure out. With just the information you gave though, a surprising amount can be worked out.
First, I would not ignore it. That it went out does not mean the errant short went away. Something caused it and that something is probably still there. More on that in a minute.
You said that only the one taillight was on. Since the taillights (running lights) are wired in parallel (they all come on when voltage is applied) then the assumption is that it must be a turn signal. That's good news. The taillight circuit goes all over the place, but the turn signal is a simple, separate wire and goes only from the trailer plug to the light housing. Much easier to troubleshoot. Second, you said it only happens on shore power. There is only one logical place that the turn signal circuit shares space with the shore power 12volt circuit and that is in the junction box beneath the front of the trailer. The shore power comes through the junction box on its way to the battery for the charge line. Mechanics NEVER say something couldn't happen, but we often start looking in the most logical place and in this case, that is in the shared space of the junction box.
My reason for not ignoring it is in the fact that the lights are led's. They work on much less voltage and only in one direction. So it can be assumed that power can't be leaking in from the ground side. If the short is still there (my money says it is) but the voltage is below 8 volts or so, then the light won't come on even if the short is active. If that short bleeds potential back upstream to your tow vehicle, it will drive the body computer nuts! The body computer (depending on your make/model of TV) will see voltage where there shouldnt be any unless the circuit is on. That will certainly set a code and warning light. You'll take your car in (without the trailer) and your mechanic will lose his mind (not to mention tearing your car down to the frame) trying to find a problem that you left sitting in the driveway.
My first thought would be to crawl under the trailer, pull the cover off the junction box and see if you can see anything amiss or touching. The connections in there ar ring terminals. Look for a stray bit of wire (we mechanics call those "smoke-circuits") sticking off somewhere it shouldn't be. Pay close attention to the yellow and green wires. They are the turn signal circuits.
It's within the realm of possibility that you have a short in the harness, but my money is on the junction box...
Let me know what you found...
WilliamA

Toby13

@WilliamA so far, no issues with warning lights on the TV (Subaru Forester). I'll have a look in the box this weekend. Thanks!

LuckyJ

Hello @Toby13

I was wondering what happen to this. Did you have a look inside the box?

Toby13

Hi @LuckyJ my apologies, I have been out of the country for a few weeks and have not had a chance to get under the trailer to have a look just yet. Hoping to get to it this week or next. I'll keep you posted!

HellFish

A couple of days ago I noticed a couple of my leds in the left turn signal were illuminated---not the entire turn signal bar. I had put the protective rubber cover over the trailer's round 7 pin connector (T@G not connected to any external power) and noticed the cord was hanging down so that the heavy rain we had that day had filled the rubber cap and was shorting some of the pins in the plug. I pulled the cap off, blew the water out of the plug and the light went out. Since then all has worked normally. Might have nothing to do with this thread...or it might.

Toby13

@HellFish that sounds exactly like what was happening! It was only a few LEDs not the whole bar, and I do recall having to dump out some water from our 7 pin connector!