Trailer Lights Not working right.

I have a 2012 Dodge Ram Pickup with a trailer package. I was using the trailer last fall and the lights were working fine when I put it away. Over the winter, I got hit in the rear bumper and the bumper was was replaced. I did a test today to check the trailer and I had a problem. Activate the right side turn signal and everything works fine. Activate the left turn signal and the all the marker lights, all the tailights and even the license plate lights flash right along with it. I got under the truck and looked at the wires going to the trailer plug and everything looked ok visually. I checked the trialer ground wire and it has good contact from the the trailer frame to the plug. I have not checked fuses in the truck yet to see if anything is blown. I did have one trailer bulb that was burned out. ( Right rear of the trailer.)

 

What is the hookup on the truck? Flat 4 or Round 7 hookup.

Check the hookup on the truck with a analog meter (digital meter is too slow) and make sure everything is ok there. You can search online for a diagram.

Then, if everything checks out on the truck go to the trailer. I would suspect the issue is there. I have put away plenty of trailers to hook them up and the lights do not work. Mice!

 

I would look, too, for the yellow wire and red wire to be swapped in the truck connector or shorted to each other (mice) on the trailer.

 

WML13,

I agree with everything that’s been posted so far, but try this. Disconnect the trailer harness and reconnect the lights and signals back to the pickup normally. Now if the lights and signals work the same way (on the pickup as they did when the trailer harness was hooked up) you most likely have a defective multi-function switch (aka combination switch).

Thank You
Amy

 

I checked the fuses on the truck (all ok) The connection is a flat four in the Truck's bumper. I tested the turn signals by gounding one probe on the ohm meter on the ground terminal and the other on each other contact in turn. The right side turn signal was a solid max hit on the ohm meter. the left side turn signal was a weaker hit. I also put the probe on the center contact in the truck plug. I was getting a reverse peg on the meter on the center contact when the left side turn signal was hot. I got nothing on the center contact when the right side turn signal was hot. If that still sounds like a wire swap or a short in the plug to you, I will take it out of the truck. (I could not find any wire damage in the trailer. I can see all of the light wires.)

Thanks for the replies!

 

My concern with the swapped wires was the accident you incurred. If the bumper was replaced, they possibly had to rewire the plug, and could have placed a wire in the incorrect position. Yellow = left, Green = right, Brown = tail, white = ground. I'd double check that.

 

It was the only thing that changed from when I parked the trailer. I know the trailer was lit up right as I check it EVERY time I use it. Thanks for the color codes. I cannot wait to get under that truck again.

Thanks again! (I will let you know how this comes out.)

 

Everything checked out with the truck plug. Went out to my farm where the trailer is, and hooked up. Left Turn Signal flashed back into the running lights, and made both truck lights blink as well as the license plate lights. I did an inch by inch inspection of the wire, and found a few questionable burned wires, but since I was getting nowhere, and was in the area anyway, I disconnected the ground connection near one of the running lights. That was it. When I reconnected the white wire for the trailer gound connection, everything stopped flashing innappropriately. I assumed that I had a good ground based on an initial ohm meter check beween the ground wire and the trailer frame. I won't make that mistake again.

 

Glad you found it out and got things rolling again.

 

It wasn't caused by those blue wire taps was it? I had a new trailer that was giving me problems one time and one of the blue taps was the culprit. Hit both wires.

 

Strange that you should mention that (blue wire taps) I had actually thought that may be it also considering that I had the side marker light where the ground wire was was also located (flashing with the turn signal). I disconnected the blue wire tap and STILL had the marker light flashing so I was down to the white ground wire again. If there is an electrical engineer out there that could explain to me why the ground is so critical in this application of trucks pulling trailers, I would sure be glad to hear from them.

Thanks everybody!

 

Much of your signaling comes from your ECM (Electronic Control Module), basically a computer. Computers love grounds and will work erratically until they find one. Even back in 1986 I had a Nissan Hardbody PU and the grounding wire from the computer to the body had a nut missing. Every time I took a really sharp right turn, the wire would fall off the stud and the engine would die. Once it fell back in place, off I went. Took the dealer replacing both throttle bodies, electronics out the wazoo, and bingo, a mechanic happened to look under the right interior panel and found the wire. Nutted it on and it was good.

It may be similar in your instance.