Problem with trailer lights / headlights on

[Jimbrownle]

I have a 24' Four Winns trailer, and this summer have started having problems with the lights. I've resolved a number of issues, but still have one problem I can't resolve:

If I have the headlights on, none of the lights work. With the headlights off, the brake and turn signals work properly. I have two different tow vehicles, and it problem happens with both, so I don't think it's the tow vehicle.

I tried replacing the ground to the trailer, by drilling a new hole and installing a new ground screw - didn't help.

I put a continuity tester on the wiring without a tow vehicle hooked up. I get a signal when I put the tester on the white (ground) and brown (running lights). I don't get a signal when i test the turn signal/brake lights. I assume this means that somewhere in the wiring the brown and white are crossed.

Short of replacing the whole harness, is there another way to toubleshoot this? Am I thinking about this the right way?

 

[Silvertip]

Re: Problem with trailer lights / headlights on

The brown and white wire are not crossed. If they were you would be blowing fuses. The white wire you properly grounded to the frame means electrically, the frame is a very large white wire that serves as the ground for the shell or ground side of all bulbs in the system. Each light fixture must have a ground connection either to the frame or to a white wire in the harness. Most lights achieve ground when the fixture is bolted to the frame. But since all lights fail to work, I doubt anything in the trailer ground system is bad. I would however be suspect of the white wire connection at the plug. If your trailer has a tilt feature that joint can break the continuity of the two parts of the trailer so that joint should have a bonding wire across the pivot point.

 

[Jimbrownle]

Re: Problem with trailer lights / headlights on

Thanks for the info. The ground (white) is part of a new 4 flat connector harness, and run to the main part of the frame, so it should be providing a good ground (although I don't know how to test that). It is not a tilt trailer.

I've tested the connector out of the truck, and it is working properly.

 

[Thad]

Re: Problem with trailer lights / headlights on

It sounds like your common wire (the brown one) is shorted out on the trailer somewhere. It gets power when the lights are on only. When the power comes on, it grounds out on the frame and there ya go...nothing works because there is no more ground.
If you cannot see it at any point that wire may come out of the trailer, side marker lights, centeer marker light at the rear, or the tail lights, then you would be time ahead to run all new wire throughout. It is not difficult or expensive but it saves a lot of headache down the road.

 

[Splat]

Re: Problem with trailer lights / headlights on

If the brown wire was shorted out you would be blowing fuses in the truck.

This still sounds like a bad ground issue. I would start pulling the fixtures one by one and cleaning the mounting points as well as the area where they attach to the frame. You want the4 contact area clean with no rust or paint, shiny is the key here.

You can even apply some di-electric grease on the connections. Next I would be pulling the bulbs out of each fixture. Look for corroded contacts, and clean them accordingly, once again apply di-electric grease to the contacts while re-installing the bulbs.

Your having a back feeding issue, it's caused by a bad connection sopmewhere.

Is the contacts on the truck, as well as the trailer plug clean? If not clean till shiny and apply di-electric grease.

The new ground connection you made on the trailer, is that clean to the frame?
Bill

 

[Jimbrownle]

Re: Problem with trailer lights / headlights on

I think the ground to the frame is clean. I ran a new harness to the truck, drilled a new hole in the main part of the frame, and ground off the paint so the terminal goes straight to metal. I'm using a new 7-4 way adapter, and the problem occurs on my Jeep and also my Surburban, so i don't think the issue is the electrical connection on the tow vehicle.



Based on the great feedback from people, it looks like it's either a problem with the brown wire shorting or a problem with the ground.

It seems like it would be a little easier to isolate the problem by running a new positive (brown) wire to each light, (without running all through the trailer). This should let me eliminate the variable of potentially damaged wire, and determine whether the brown is the problem, or the ground. I can connect one light at a time, to confirm that the increasing load isn't causing some type of problem.

If connecting new brown wire doesn't solve the problem, then it implies that the problem is the ground. It seems like I should also be able to run a direct ground wire to the fixtures for testing, again using spare wiring, to eliminate the variable of the trailer frame. If that solves the problem, then it's the exercise to clean and/or replace as needed.

Does that sound like a reasonable approach?

Thanks again,

-Jim

 

[Thad]

Re: Problem with trailer lights / headlights on

I hold to my original assessment.

If you have turn signal and break lights then your ground is good.
Try this, hook only your ground on the plug. Leave the rest unhooked. Use a jumper wire from your common (brown) on the truck, to your right and left plugs on the trailer end. The tail lights should come on respectively.
To double check, Take the jumper from a left or right on the truck and put it to the common on the trailer plug. In theory, with all things proper, side markers and tail lights should blink. I will say that in your case, nothing will happen.
If you want to run to each light, be sure to cut the brown wire from that socket. Otherwise, all you have done is take the long way around to send power back to the short.
As far as the fuses go, there is not enough draw, even with a shorted wire, to blow what is most likely a 20 amp fuse.

I never give advise, only opinions
That way, it does'nt hurt if I am proved to be wrong.

 

[Silvertip]

Re: Problem with trailer lights / headlights on

Ohm meters are used to verify grounds. If you don't have one or know how to use it, use a short piece of wire and touch one end to the trailer coupler and the other end to the trailer hitch on the truck. If the lights now work you have a bad ground.

 

[Silvertip]

Re: Problem with trailer lights / headlights on

Ohm meters are used to verify grounds. If you don't have one or know how to use it, use a short piece of wire and touch one end to the trailer coupler and the other end to the trailer hitch on the truck. If the lights now work you have a bad ground. I've heard of many issues with the 7 to 4 pin adapters as the 7 pin end is not always wired uniformly among manufactures.

 

[Home Cookin']

Re: Problem with trailer lights / headlights on

a mystery I had on my Chevrolet Tahoe was that a white wire in the vehicle harness, that one would assuem was a ground wire, was for a third brake light (like the one in the middle of the tailgate) but it was bolted to frame, causing feedback when you ahd lights on, and then hit brakes. Took days to figure out. At least that's how the one mechanic who fixed it explained it.

 

[Thad]

Re: Problem with trailer lights / headlights on

I think what every one is missing here is; his turn signals and break lights work. Therefore...ground is good. When the vehicle lights are turned on, nothing works, therefore... common wire that feeds the tail lights and side markers is shorted out somewhere in the trailer.

If it were a socket or bulb, it would only affect that particular fixture.
It occurs with two separate tow vehicles so you can rule out any problem there.
You can argue ground, but even so, at various times during tow, the lights would flicker due to being grounded (poorly) through the hitch.

I will go on record stating again..."I hold to my original assessment."

 

[Silvertip]

Re: Problem with trailer lights / headlights on

Ground does not have to be good to have some of the lights working. There are many trailers that seem to have good turn signals or running lights until you step on the brake at which time they fail. That, and this function is very typical of a bad ground. Electricity will get back to ground wherever it can. So far, we don't know if the truck is wired correctly or if the trailer is wired correctly. So its about time that was done. Disconnect the trailer and get out your battery charger. Connect the negative lead to the ground screw on the trailer frame. Put a nail in the clamp on the positive lead. Plug in the charger. Touch the nail to the brown lead on the trailer plug. All running lights should work. If none of them work, you have a brown wire issue. If some of the lights work, then there is an issue with each of those that don't. Then repeat the test for the green and yellow wires. Only the brighter filament (brake/turn) should be on for the side you are testing. If these three tests are ok the problem is with the truck. As I pointed out earlier, there are a couple different types of 7-4 adapters. Plug in the adapter and turn on the headlights. Use a test light or voltmeter to verify that the corresponding running light pin (for brown wire) in the adapter is active AND that none of the others are. When you make this check, measure using the actual ground and running light pins in the adapter, not the truck frame. If this is ok repeat the test with the four-ways on. The left and right terminals in the adapter should be flashing. Lastly, do both of your trucks have amber turn signals. If so, there is a good chance you need a converter. Trailer lights have the brake and turn signals on the same filament fed by one wire. If the trucks have separate turn signal bulbs, the brake and turn signals are served by two individual circuits. This system is not compatable with standard trailer wiring without the use of a converter.

 

[swordfish25]

Re: Problem with trailer lights / headlights on

Try hooking the trailor plugs together without the trailor hooked to the truck, if the signal and brake lights work the right way, then the ground is ok. You must have a brake in the tail light wire, Make sure there is power on the brown comming from the truck. Late model vehicles have seperate fuses for the trailor lights, tail and signal. There is a fuse panel under the hood on most vehicles. Good luck

 

[captharv]

Re: Problem with trailer lights / headlights on

I would 1st verify the grounds at the lights themselves. My 2 yr old trailer had a problem with one side not working. They are LED lighting on the whole trailer. The left side did not work either for the runnning or turn. I put a wrench on the ground lug nut and it worked. Since, I took them loose and dremmel wire brushed under them and retightened. Then, coated them with urthane.
2nd. Hook up the trailer lights without connecting it to the ball. Then try the lights. Then, use a car battery jump cable between the vehicle chasis and trailer frame. The trailer may have a bad connection to the ball mount, electrically, and the ground on the white wire is not continuent. I I would stronly suggest buying a digital volt-ohmmeter. We can talk you thru this, but need you to make measurments for us, as we are not there.

I am still with a corroded connection somewhere, or the grounding in the car is not being grounded to the trailer.
Or, the 4/7 adaptor is not kosher somehow.
Note: My trailer has the turn sigs, running lights, and a backup light connections on it (disk brake disconnect in reverse). I got tired of that adaptor, soo I cut off the plug, went to walleys world and bought a 7 pin RV connector ($8) and wired it in. besides working right, it LOOKS a lot more heavy duty (read-- truck).

 

[wyocoyote]

Re: Problem with trailer lights / headlights on

It sounds like your common wire (the brown one) is shorted out on the trailer somewhere. It gets power when the lights are on only. When the power comes on, it grounds out on the frame and there ya go...nothing works because there is no more ground.
If you cannot see it at any point that wire may come out of the trailer, side marker lights, centeer marker light at the rear, or the tail lights, then you would be time ahead to run all new wire throughout. It is not difficult or expensive but it saves a lot of headache down the road.

SAME PROBLEM in a similar situation. I think Thad has nailed it, I'll double check today and repost yea oy nay.
I have a hitch mounted box with trailer lights on it made be Wheeless Trailers of Colorado (I also have a similar Thule Terrapin cargo box) SAME AS WITH ORIGINAL POST: my trailer lights work only when headlights/running lights are off. When they are off the brake lights and the turn signals both function. Turn them on y nada limonada. This is not the best scenario: no signals or brake lights at night.

I see that Thad recognized the clue that the lights work when headlights are off: I am going to follow his lead. Now I must admit I dont understand why the shorted or crossed common could cause this situation.
I do understand why fuses don't blow, there is no inline fuse or is just not enough a problem to blow them.
Other clues applicable to my situation.
1980s 4runner. The trailer lights were just wired by a "pro"(so that cant be ruled out pro or no)
Oh yeah there is corrosion where the lights go in, wicked burning man dust you know, maybe some pixie dust will solve this.
my bulbs are the two way ones: two filaments versus seperate bulbs. I used some other trailer lights i have to trouble shoot and they did fine. (but they may be a different set-up could be apples and oranges)
I'll be cleaning things up and trouble shooting today.
hope to confirm Thads assertation, will post results if i dont pull my hair out trying.

 

[JB]

Re: Problem with trailer lights / headlights on

Coyote, you are violating our rules by replying to a 3 year old thread. If you have a problem please start a new thread.