Trailer lights acting weird?

hooked up my utility trailer. checked lights, all worked fine-brake, and both blinkers.

Then it got dark and AUTO setting turned on my headlights.

Now, only right blinker and taillight work? Left one, nothing?

Checked everything twice-fuses, connections, ground, etc

When I manually turn lights off at dash, then everything works again?

noticed that the RT LED indicator light on trailer harness is off, but TM and LT are on?
tried disconnecting trailer ground wire and then all 3 LED indicator lights are on?

so, obviously there's a problem. tried switching bulbs from left and right, same result.

3 wires going to back of trailer-LT, RT and TM (this wire runs directly to right trailer light and wire to left light taps into it)

I guess it's possible that there's a short in left trailer light assembly?  but, it works fine when vehicle headlights are off, so it is getting power.


Any ideas?

Sounds like the running/marker lights are causing the problem (that's the brown wire) try disconnecting it and and see if it brake/turn work normal. The brown wire should only be connected to the running lights not the stop/turn light circuit (left yellow, right green wire).


Good luck...


Edit... And make sure the ground is good, that's the white wire..

Brown wire is independent. It runs from trailer harness plug back to right trailer light and it is split before the light to the left trailer light. I'm going to take off the left light tomorrow and check the brown wire connection to it.

You can check at each location what you are getting for voltage with a VOM.

Your lights use the trailer body as its ground and should only have two wires running to each side.
Check if your light has a ground wire. Sometimes they do and you have to run this to the body of the trailer. Probably where the light bolts to the trailer frame assuming it is metal.

The brown wire goes to both sides and is your running lights.

The Yellow and Green wires are your turn signals as already mentioned.

If for some reason one of your lights is not grounded properly you can have some weird lighting combinations because the light will actually ground through the other light(s).  And if you have +12 volts on each side of a bulb they won't light...

Rodney

I'll check that.

Here's your basic trailer wiring set up, like all have said check each ground, which is at every light usually with a rivet or screw which can easy become loose or corroded and make poor contact..

your diagram is accurate, except that it shows a 5 pin, as opposed to a typical 4 pin flat that most of us use.

The brown wire is typically split at some point along the way, as opposed to having 2 leads from harness.

I didn't think to check the grounds on the lights? I just checked the main ground on trailer.

Since the right light is working properly, but not showing up on LED test light,I'm thinking that it has the bad ground? It could be grounding itself through the brown wire back through the left light, which kills off the left light.  Make sense?

Thanks for the help!

Check the grounds of ALL of the lights in your trailer system. I do checks on trailers we have at work and bad grounds can make all sorts of weird combinations. Not always making sense what is doing what. So make sure you check all ground points. The main trailer ground and all lights. Yes including the marker lights...

Rodney

gitnby said:

your diagram is accurate, except that it shows a 5 pin, as opposed to a typical 4 pin flat that most of us use.

The brown wire is typically split at some point along the way, as opposed to having 2 leads from harness.

I didn't think to check the grounds on the lights? I just checked the main ground on trailer.

Since the right light is working properly, but not showing up on LED test light,I'm thinking that it has the bad ground? It could be grounding itself through the brown wire back through the left light, which kills off the left light.  Make sense?

Thanks for the help!

Click to expand...

I don't know what diagram you are looking at but this one is a 4 pin. you can split the brown wire behind the tongue or at the connector  ? yellow, green, brown and white 4 pin. Wheres the 5 th wire?  Better take another look it kinda looks like it has another pin but it does not..

Finally figured it out!

Actually, there were 2 problems.

The green wire had rubbed against the metal bracket that light was attached to, and had a small exposed spot that was touching the frame. Re-wired it.

Then I ran a separate wire from the left tail light to frame and re-grounded it.

Everything worked fine.

Those tail light assemblies that are supposedly 'self-grounding' to the bracket aren't very reliable?

Ran to O-O-O O'Reilly's. Needed some new fuses after all of my screwin around with the darn thing, so I decided to go ahead and pop for an all new kit. $24.95

The new kits they have are a snap! Everything you need, and more! Light assemblies are great, has ground wire on each light that goes right over bolt and harness has brown wires from plug running alongside both yellow and green wires. Now I know my wires are good all-around.

Next time I have a problem, and it takes more than a half-hour to figure it out, I'm spending the $24.95 and another half hour to install all new wiring.

My free time is definitely worth more than my labor rate!

Glad you found the problem/s, sometimes it can be a real pain chasing shorts and loose connections..

Randy said:

Glad you found the problem/s, sometimes it can be a real pain chasing shorts and loose connections..

Click to expand...

There's got to be a country song in there somewhere?


" I was hopin' you would come back to me, Dear, and shower me with warm affections,

But here I sit all alone, drinkin beer, chasing shorts and loose connections"

LOL.... Yea I think they are sisters..