Trailer lights not working - help please

[Gadgetman]

On the way back from Leech this weekend my friends in the vehicle behind me call and say my running lights just went out. Sure enough my tail lights and side marker lights are suddenly not working. I have brakes and blinkers but thats all. I have a 5 flat connector that plugs into one of those round plugs on my Yukon. I scrapped on the area that the ground wire screws on to the tralier but no luck. What next? I have a circuit tester but not sure what end of the trailer to start on.

[jeffreyd]

well you could use the tester, to see if you have a ground issue. What kind of vehicle is it? I would look to see if they tied the marker lights in as one unit and where they catch the ground. also you should to see that the trailer running light fuse in the box did not blow. could be also that the wire pulled off the screw or broke in the plug especially if it were pulled on by the cord. The plug would be the easiest place i think to start. good luck.

[Gadgetman]

Its a Chevy Yukon - the tail lights are the kind that have the bulbs in a plastic capsule so they are water tight.There is a green and brown wire that runs down one side and a brown and yellow that runs down the other side. The wires run inside the trailer frame so I cant see them, but would assume they are in good shape. All the holes in the trailer that the wires run thru have rubber grommets on them as well. I guess I will start on the front and concentrate on the grounding connection on the trailer.

[Smoker]

I have had the plug adaptors go out on me. It was a turn signal on mine. I had a extra one so I tryed it and everything worked fine.

[jeffreyd]

i would also check the fuse block in the engine compt to see if you lost the fuse up there for the trailer lights.

[BoxMN]

did it blow the TRL fuse in your Yukon? That is first thing to check. We had to rewire the port side of our Shorlandr trailer (13 years old) because we traced it to that side, and only the side markers and running lights, not turn or brake. I believe it was the brown on port side for us. I think caused by the corroded middle light bar, which came off the port side brown.

If you had shorelander trailer and find it is the pulg or the wire itself, you can buy the harness segment for about $12. You could wire it yourself for much cheaper, but for us it was just easier to slap the new one in.

Good luck! Tracking the problem is the hard part, fixing it is easy

[walleyemaniac]

I would start at the Vehicle side of the plug. Turn on your lights and make sure you have juice to one of the terminals. If everything is dead it's in the vehicle. I'd start with fuses then check wires at the plug.

If you have juice at the plug, Plug the trailer in and start as close to the plug as you can get with the brown wire (that is your clearance and tail light wire) work your way back.

If all clearance and tail lights are out I'm geussing it's at the plug or before. Check to make sure your ground is good on the vehicle and on the trailer. Ground thru the plug not thru the hitch.

[hanson]

When I wire a trailer, I run ground wires all the way back to all the lights. That totally eliminates that problem, which is probably the most frequent and common issue with a trailer light problem.

The way your trailer is wired, the trailer frame IS the ground wire for the entire system. Most of your lights are probably grounded to the frame with the mounting screws. Some lights have a ground wire that you screw to the frame but most ground through the mounting bolts. If these connections rust or become loose, you'll have a big issue to track down.

So you've cleaned off the ground wire from the truck to the trailer. Now go through every other light (heck go through them all) that is giving you issues on the trailer and make sure it has clean metal to metal attachment to the frame if it is grounded through the bolts. If it has a white ground wire that is attached to the frame, make sure that is clean as well.

I'd bet the problem is in your trailer and not the truck.

I seriously don't understand why white ground wires aren't run all the back to all the lights on trailers, then you'll never ever have a grounding issue. Its simple, it can't cost a heck of a lot more, and it'll solve a lot of problems down the road.

[Surface Tension]

If your turn signal/ brake lights are bright it isn't a ground issue.

Check the fuse like suggested.

Clean the plugs.

Check for voltage on the brown wire.

Start at the plug for voltage from the brown side of plug.

[Gadgetman]

Put the voltage tester on the plug adapter and the top two holes caused te the tester to blink when I had the flashers on the third hole (just above the ground) didnt light up the tester at all. I think the problem may be in the big round plug on my vehicle that the plug adapter goes into. I got a friends plug adapter and got the same results when i tried it. Will try cleaning the connections on the vehicle plug and see if that helps - will keep you posted