2nd Gen Non-Engine/Transmission Need Trailer Wiring Help

[Muleskinner]

I need help with a trailer wiring issue on my 01 2500 Dodge 4X4. As this is a new issue I have replaced the two rear 1157 bulbs (Stop and run), checked all of the trailer wiring, including the ground connections, and truck wiring.



The problem is the running and side marker lights stay on with out the truck lights on. (Somewhat dimmer) If I unplug the trailer plug the lights go out. If I leave the trailer unpluged for about one hour the trailer lights don't come on when I plug in the trailer wiring to the truck. But, if I reach inside of the truck and turn the lights on, the trailer lights stay on again when I turn off the truck's light switch.



Now. Using a test light I find two wires in the truck's factory trailer light plug with twelve volts. The battery wire and the running light wire. Anyone with any ideas? I unpluged the "Trailer" relay under the hood while the lights are on with no change.

 

[AKAMAC]

Looks like a ground problem. You can check resistance at each socket or test by removing each bulb until you lose the lights. Once you find the offending socket just make sure that there isn't any corrosion on the ground. Hope this helps, Mike

 

[2-ND TIME]

trailer wiring

Sorry not to be more up on trailers but.

Q. You have a battery in the trailer? Is it then wired to the trailer wiring? Is it mis wired in to the trailer harness somewhere? Is it isolated from the trailer?

If not is there a place that the trailer brakes wiring could be spliced in to?And back feeding?

Shall try to help more if I can.

 

[AggieJustin]

Using a test light I find two wires in the truck's factory trailer light plug with twelve volts. The battery wire and the running light wire. Anyone with any ideas? I unpluged the "Trailer" relay under the hood while the lights are on with no change.

So even with the lights off, the truck's plug has 12V on the marker light circuit? If that's the case, I'd start checking the truck's wiring for a short between the +12V circuit and the marker circuit.

The problem is the running and side marker lights stay on with out the truck lights on. (Somewhat dimmer) If I unplug the trailer plug the lights go out. If I leave the trailer unpluged for about one hour the trailer lights don't come on when I plug in the trailer wiring to the truck. But, if I reach inside of the truck and turn the lights on, the trailer lights stay on again when I turn off the truck's light switch.

This sounds like the lights are being fed from a secondary power source on the truck that loses charge after being off for an hour. Have you tried leaving the trailer plugged in with the truck lights off to see how long they stay on? Although I'm not sure what is storing the charge when you power up the marker circuit. Are you the first owner of this truck? Or is there a chance someone else might have tinkered with the wiring?

 

[Muleskinner]

I'm the original owner of the vehicle. A ground problem was the first thing I thought of, but I was unable to find a problem.



If it was the battery for the emergency electric brake feeding the circute, would it not keep the lights on when the trailer wiring was unpluged from the truck?

 

[AggieJustin]

Exactly, the source of the "phantom" power is in the truck since when you pull the plug the lights go dead on the trailer (this is confirmed if you still have +12V on the marker light pin of the truck plug).



Another thing to check is to pull the trailer relay and check both sides of the relay socket with a test light. You should only have +12V on the supply side of the relay socket. If you also have +12V on the load side, then you've confirmed that you're backfeeding power from somewhere between the relay and the plug.

 

[J.BURCHFIELD]

I need help with a trailer wiring issue on my 01 2500 Dodge 4X4. As this is a new issue I have replaced the two rear 1157 bulbs (Stop and run), checked all of the trailer wiring, including the ground connections, and truck wiring.



The problem is the running and side marker lights stay on with out the truck lights on. (Somewhat dimmer) If I unplug the trailer plug the lights go out. If I leave the trailer unpluged for about one hour the trailer lights don't come on when I plug in the trailer wiring to the truck. But, if I reach inside of the truck and turn the lights on, the trailer lights stay on again when I turn off the truck's light switch.



Now. Using a test light I find two wires in the truck's factory trailer light plug with twelve volts. The battery wire and the running light wire. Anyone with any ideas? I unpluged the "Trailer" relay under the hood while the lights are on with no change.

The somewhat dimmer suggests a ground problem which might be uncovered by use of a continuity tester. There might be an issue with a circuit breaker. A test light is OK in some places but a digital voltmeter is better so as not to disturb the computer. Also it might tell you how much voltage you are getting when the lights are burning dim. There is a wire that stays hot at all times where you plug in the trailer cord. It could have been connected to the wrong terminal and tripping the ciruit breaker if they used one like on the headlights. There might be a wiring diagram in the shop manuel for your truck. Or the store that sells the trailer plug may have a diagram. It can be a real head scratcher.

 

[Rams-n-Hogs]

The first thing I would do, is disconnect the battery from the emergency trailer brake battery, and see if the symptoms change.



Jim

 

[Muleskinner]

And if they do?

 

[MBFARMS]

1- get a standard wiring diagram for the plug that you are using

2- test all the wires on the trailer to make sure they are where they are supposed to be in the plug.

3- check all the wires on the truck and make sure they are in the right location.

4- find the ground on the trailer frame, put a new connector on the end of the wire and use a self tapping bolt to make you a new ground.

5- Find the ground on the truck make sure it is in good shape.

6- Unhook the battery on the trailer, just to see if the problem still occurs

7- check both plugs for wear or corrosion. I have seen plugs that somehow manage to make a connection to other terminals.



Here is a place to get the wiring digram.

http://www.etrailer.com/faq/wiring.asp

Good luck.

 

[Loren]

I will second what MBFARMS says. I have had connections (usually ones that I wired myself) where a single strand of wire bridges two terminals inside the plug.



Check for this. It may explain the low voltage.



I don't know why the lights would eventually go out, but it sounds like a capacitor is getting charged and then slowly losing its charge.



Good luck. Sure hope you find this.



Loren

 

[Muleskinner]

Due to time constraints I was unable to diagnose the problem this weekend. However, I now know the problem is in the truck, as my wife's horse trailer lights stay on the same way when plugged into the truck. :-laf

 

[Tiger Rag]

I'm having the same exact problem. I have one new trailer that I thought was the problem. I have another trailer that has never had this problem and it occurs with both. I am also using the same brake controller I used before, I just moved it to my 01 2500. I'll post a reply if I find the problem.

 

[Muleskinner]

Now as if like magic the problem as corrected itself. I'm really puzzled now. Nothing I did. I had not had the chance to work on it yet.

 

[Tiger Rag]

Well, I guess I'd better just hope that my truck fixes itself too. I haven't had a chance to look deep into it, but I was hoping between the two of us we could figure it out. I thought I had a bad fuse, but that's not it. I checked it today for continuity and it is fine. I do have to pull it out to get the parking lights to go out. It all seems to have started after wiring my brake controller. Maybe I did something wrong, but I just can't see how. All the wires are color coded and match up exactly with the wiring harness..... I'll update if I get a fix. For now though, it has affected my parking lights whether the trailer is hooked up or not. I have to pull the fuse regardless after turning off the headlights.

 

[2-ND TIME]

You have problaly thought of it but the one side is male and the other is female? Started to do that once upon a time. (big grin)

Recheck the plugs wires. Does the DC voltage jive with trucks plug ins? or wires rubbing in the loom some where? (bad splice somewhere)

 

[Muleskinner]

Interesting. My truck lights have never been effected by this problem?? That's what so wierd! Power on the running lights post in the trucks trailer wiring loom plug, but the trucks lights don't come on unless turned on by the switch.

 

[cwcox]

Pull the truck end of the trailer harness connector out of it's mount on the hitch. Pull it apart and check condition of wiring inside. You may have corrosion building up and creating a circuit between the battery positive feed and the running light feed terminals. If not in here, pull harness apart going back to frame, often corrosion in this area. Also check to see if your truck has the extra pigtail for the goosneck/5th wheel hitch- it comes out of the harness up near the front of the fuel tank. This could be pinched,corroded,etc. Lastly, pull the power distribution center (large fuse block under hood) off the fenderwell and pull covers off. Inspect the wiring that goes to the trailer lighting relay- look carefully as you'll probably find a small pinch/rub through to power in here. Hope this helps- good luck!

 

[Tiger Rag]

I've got one thing I'm going to try... ... take the brake controller off and see if that fixes it. Not sure. If it doesn't, I've got a friend that is going to help me this afternoon.

 

[Tiger Rag]

Well, taking the brake controller off didn't work. My buddy and I couldn't fix it. It appears the controller is doing what it is supposed to. I've got an appointment at the Dodge dealership in the morning... ... ..... :--) :{