Trailer lighting problem...

[CALVINIST]

The problem is this: the only lights that work are the running lights. Blinkers and brake lights do not work.

Things to consider...

1. New wiring put in just last year.

2. New lights put on just 3 weeks ago.

3. When I first encountered this problem, I hooked up the vehicle end to a different trailer, and all the lights worked on the trailer, so I know the problem isn't on the vehicle side of things.

4. Once I determined that, I bought a new connector for the trailer, just in case I had a bad connector. The result is the same. Running lights are all that work.

5. The whole thing was working just fine after installing the new lights.

6. I checked the vehicle fuses and all are ok.

I am puzzled about this. Anyone have a clue?

[PierBridge]

Simple bad ground.

Airjer can explain it better....but I'll try.

My trailer lights were working just like yours last week, first off I re-grounded the light hookup on the trailer I pulled the phillips screw out and I took a grinder and got down to the bare steel on the trailer I then attached the white wire back to the frame, then I removed the rear trailer lights and grounded/sanded those areas down to the bare frame so the nuts, and bolts would have good contact with the frame.

Bingo..... all lights working.

[CALVINIST]

Yeah, my trailer is a bit crusty. Thanks Pierbridge, that sounds like a simple, cost-free solution. I'll give it a whirl and report back.

[MNice]

With 12V system problems, 99% of the time it's the ground.

[Jeremy airjer W]

The other lights are working and did not stop working when the brake lights where turned on which implies that this is not a ground issue. It could be but typically if the ground is bad nothing will work or something will be quirky. The place I would start is the sockets for the tail/stop lights. With the trailer hooked up to the vehicle and the running lights on and someone stepping on the brakes, check for power at the two bottons in the bottom of the socket. They should both light up. If they do than I would say there is a stronger possibility that the ground is suspect. If one doesn't than we have an open circuit. If this is the case I would start backprobing that circuit starting at the front and working my way back until I lost power. Repair the broken or corroded wire and your back in business!

Good Luck!

[fish-n-geek]

Running lights sometimes still work on a bad ground. The "dead" brake/turn signal wires can leak enough current back to complete the circuit, I believe. I've also had trailers where I could light up the running lights with no ground at all.

-r-

[efgh]

Did you check the bulbs? The feliment in the bulb for the stop, blinker is longer, on rough roads the feliment breaks on the stop, blinker side, then you have no break or blinker lites. I live on a gravel road and when it gets washboardy, I some times find a stop that doesn;t work. You can buy heavyer feliment bulbs if this is the case.

[tonyjor]

also, make sure you have the bulbs with two filaments. I made the mistake of buying single filament bulbs once and only the taillights worked, no brakes.

[Sandmannd]

I had this same problem with a trailer I had this year. Turned out it wasn't the wiring, it was the adapter on my truck. I have to go from round (on my truck) to the 4 pin. Got a new adapter and it worked great. I know you said it worked with another rig, but it was a cheap $10 fix for me.