Trailer running lights

[jigrig]

My trailer running lights aren't working. The turn signals and brake lights both work. The last time I went out, the running lights worked and now last night they won't come on. Any ideas?

[Musky hunter 82]

Check the ground connection it should be the white wire. If you don't have a good ground none of the lights will work.

[pike79]

Try a different vehicle it could be the fuse in your vehicle. I had the exact same problem two years ago and replaced the fuse in the truck.

[delmuts]

+ 1 to the two posts above!

I got tired of dealing with ground problems and trailers; so i now run a wire from the ground side of my batt. to the plug.

As said. Try a different vehicle or use a test light to be certain you have power to the plug.

[Dragonsm]

It could be something as simple as a little of that green/blue corrosion gunk on the running lights terminal. (either coming off the vehicle or on the trailer plug)

Last weekend I had turn and brake lights...but no running lights. Cleaned both the truck 4 prong plug and the trailer, plugged it back in and had lights.

Steve

[fish_eat_sleep]

my vehicle had an aftermarket trailer wiring harness that used spliced tail light wires to get power. one time a wire corroded and needed some grease and a different splice location. about a year later it shorted out and the 4pin plug melted a little. so i left the boat at home. went over to o'reilly to order a better aftermarket part that used the plug-in style connection. but when i started my vehicle smoke filled the car, out from under the passenger side dash. i later found out that the thing fried when i started the car, and also fried a wire under the dash, along with the fuse to the running lights on my car and trailer. my headlights and brakes worked just not the marker lights and running lights.

Im no expert but heres some ideas.

If car lights work but not trailer check the ground wire, and the 4pin plug connections. also if you have a 7-4 converter check that too. buy a $2 4pin plug tester if you need to..

If your marker lights don't work on your car. check the fuse panel, and possibly replace the aftermarket wiring harness on your vehicle if you have one to prevent the fuse from going bad again..

[jigrig]

That's why I'm confused because both turn and brake both work.

[shamrock7]

If your trailer brake and turns are working your ground is not the problem. As said before, make sure you have running lights on your tow vehicle. If not, fix that first. Then check for voltage at brown wire on you trailer plug, if no voltage, check the vehicle side of the plug for voltage on the brown wire. If still nothing, you have a bad connection in the vehicle wiring. If you have voltage on the trailer side of the plug, keep checking further up the trailer frame until you find your problem.

[fish_eat_sleep]

I guess i forgot to add in my original reply that my vehicle has 2 separate fuses, one for the running lights (red tail, white reverse & yellow front markers) and a totally different fuse for the headlights and brakes. (probably for safety reasons) when my aftermarket wiring harness went bad it only effected the running lights. my head lights worked and so did my brake lights even on the trailer. thats why i thought our situations could be similar and that maybe i should chime in.

when your headlights are on, do your yellow marker lights next to the headlight work on the vehicle? (yellow markers, turn signal bulbs).

Do your tail lights on the vehicle work when the brake is NOT applied?

This would give a clue to what fuse is bad if there is one. and why only half of the lights randomly don't work on the trailer.

For me, it took a $40 harness for the vehicle (in the trunk behind the tail light and side panel).. and a $1 fuse under the hood of my car. nothing was wrong with my trailer at all.

[1johnb]

Anyone who pulls a trailer should have a test light. They are an inexpensive tool that can save countless hours of trial and error. You can try all the suggestions if you want to. Get a test light check for power at.. the vehicle plug. A four wire harness will be. Brown /tail marker - green /right turn and stop -yellow /left turn and stop -white/ ground. Check the brown terminal for power and then check all splices or junctions. DO not probe the insulation you will regret it later. I have 30 year's in the truck repair business, believe me a circuit tester is very valuable

[EBass]

You did check the bulbs right?

[jigrig]

It was a 15 amp fuse that was blown. It was in the fuse panel under the hood. It was labeled "trailer parking".

Thanks for all of the help!!!