Trailer Lights dark when headlights on

[summerwind1991]

I have 1993 shorelander, used trailer, turn signals work, brake lights work, but when it comes time to turn on headlights for evening travel, the associated trailer lights do not light up.

 

[JB]

Re: Trailer Lights dark when headlights on

Tail (running) light circuit is not connected.

 

[Silvertip]

Re: Trailer Lights dark when headlights on

Brown wire in the harness is either not getting juice from the tow vehicle or its open somewhere in the trailer.

 

[Bondo]

Re: Trailer Lights dark when headlights on

Or,... The Trailer has a Marginal Ground......

 

[Pony]

Re: Trailer Lights dark when headlights on

I agree with bondo check the grounds first and trouble shoot from there. Checking for continuity before and after the plug and before and after the vehicles wiring harness to see if one of those is the culprit.<br /><br /><br />Had a trailer issue with one of mine a few years ago, and ended up tracing the problem to a wire that had broken underneath my truck right after the wire harness.

 

[Silver/Fish]

Re: Trailer Lights dark when headlights on

Also check ALL of the fuses to the trailer.(Check your owners manual if you have it.) I had the same problem...My Chevy had different fuses running to the trailer. Finally found the right burned out fuse after trouble shooting for hours.

 

[burp]

Re: Trailer Lights dark when headlights on

What kind of tow vehicle? If it's a Ford F-150, or Explorer, there is a 20 amp fuse in the fuse box under the hood that is strictly for the trailer marker lights.

 

[ZR8RIDER]

Re: Trailer Lights dark when headlights on

Mine was doing the same. We hooked the trailer to a buddy's truck and the trailer lights worked perfectly. That told me the problem must be with my Jeep. I was wrong. One bad ground on the trailer tail light was my problem. Cleaned it up and works perfect. Strange how his F150 worked and my Jeep didn't. Check all your grounds first, then dig out the test light.

 

[summerwind1991]

Re: Trailer Lights dark when headlights on

Chevy Trailblazer. I will check vehicle and trailer grounds. Thoughtful tips and advice thank you.

 

[Silvertip]

Re: Trailer Lights dark when headlights on

If the other lights work normally then a ground is not likely the problem. Check the brown wire for voltage on both sides of the plug. If its missing on both sides you have a truck wiringing issue. If its present on the truck side and not on the trailer side its a connector or trailer issue. That brown wire also branches somewhere on its way to both side of the trailer. Check that splice. Although unlikely, it is possible the tail light filament in both bulbs could be bad but I hope you checked those.

 

[bruceb58]

Re: Trailer Lights dark when headlights on

Doubt it is a ground.

 

[Pony]

Re: Trailer Lights dark when headlights on

Yes true it is unlikely a grounding issue since the rest of the lights function correctly, but it is still a very good idea to clean them now since most other trailer light issues can be traced to it. As I said before, to me its a good starting point.....then trouble shoot with continuity checks from there......by process of elimination the problem can be found. <br /><br />Have your checked to see if there are any parts of the brown wire where the insulation has worn down and is touching the frame??

 

[summerwind1991]

Re: Trailer Lights dark when headlights on

Took apart the lamps, checked continuity also. Is it a problem that the connection out of the vehicle has 5 connection points, while the old trailer only needs the 5 connection points. The brown wire connects to both tail lights and lights blinkers and breaks, but no running lights. Inside tail light is a light bulb for blinker, and one dual filiment light bulb. Could it be the light bulb? Also checked fuses in vehicle, all fine.

 

[tommays]

Re: Trailer Lights dark when headlights on

<br /><br />The trailer is a 4 wire system UNLESS you have a reverse lockout solenoid if your car uses 5 wires you need a converter to make the trailer work correctly<br /><br /><br />tommays

 

[Silvertip]

Re: Trailer Lights dark when headlights on

You are misinterpreting what the brown wire does. It is for tail lights only (dim filament on dual filament bulb). Stop and turn use the other filament. The separate bulb you mention is the rear side marker light. The fifth wire in the truck harness is not used for your trailer since it is to actuate a reverse solenoid which prevents hydraulic brakes from actuating when backing up. Follow Tommays diagram.

 

[studlymandingo]

Re: Trailer Lights dark when headlights on

Aint' trailer wiring fun!!! Works perfectly for a while, then randomly begins to act up. Fix it, starts all over again. Anyone ever had ALL of their trailer lights work perfectly for more than 1 year without any work?

 

[Silvertip]

Re: Trailer Lights dark when headlights on

Yes. My trailer is entering its third season and I've not so much as changed a bulb. I protect the wiring on day 1. Ensure the white wire and lamps have a good ground, coat those ground connections, protect the tongue wiring with flexible tubing, and use a truck connector with a water resistant cover. Unplug before backing in to protect hot bulbs. There are only four wires to deal with. Think of it as water through a pipe. If the pipe is broken, juice can't get to the bulb. If ground is broken or bad, same deal.

 

[summerwind1991]

Re: Trailer Lights dark when headlights on

I think I may have this thing narrowed down, but would like your guys confirmation. I am getting a DC volt reading on the green, yellow, but not the brown wire. Is that the problem, the fact that the running lights aren't working related to no juice feeding from the brown wire from the vehicle? Is this the problem.

 

[Reel Poor]

Re: Trailer Lights dark when headlights on

Green and yellow should only have voltage with brake peddel applied or be flashing voltage when signal is on (yellow left turn, green right turn). The brown wire is the only wire that should have voltage when the running lights are on.

 

[Terry Olson]

Re: Trailer Lights dark when headlights on

As soon as I read the title of the post I heard the words "bad ground" in my head.

You know how "the butler always did it"? Well, when it comes to trailer lighting problems "the ground always did it". Start there and you'll solve most trailer lighting problems before you have to branch out.