Trailer running lights question
 

As I was replacing a coupe of lights on the trailer, I realize that my 98 Dodge Truck has no power to the running lights, I mean the wires are connected and everything looks like it was done professionally, however the 12 volt tester shows no power on the running light pins. Only the brakes and blinker lights work.

First I though the trailer wires were bad, but connecting the trailer on the Tahoe everything works fine.

I have yet to trace every piece of wire under the truck, but from what I can see so far, the wiring looks sordid and like I said it was done by a professional perhaps from the manufacturer.

I've check the fuses and every one seem ok; I'm leading toward a separate fuse and /or connector under the firewall...

Have you experienced such problem or know of any possible cause that would lead to this?


Thanks

Joe

Re: Trailer running lights question
 

If I'm not mistaken all newer vehicles need a wire harness T connector to install trailer lights. These are usually $9-$39 depending on vehicle. If someone somewhat familier with adding trailer lights on older vehicles did it to the newer models it is likely to get the results you have. Check and see if you have this T connection, look under the truck where the main wire harness in the rear along the frame and trace the wire to the trailer lights. If so other problems exist, if not get one and install it (Walmart, etc).

Re: Trailer running lights question
 

Re: Trailer running lights question
 

The problem that usually exists when hard wireing is the use of blinker and brake lights. NOTE that the trailer has a combo brake and blinker whereas most vehicles have a brake light and orange blinker, so a converter is needed. In some instances when the vehicle has a combo brake and blinker a converter is still needed because of the way the vehicle seeks power.
I have seen one instance where the owner did not want to purchase the T but did install the converter and still had problems, once he installed the T and harness all problems ceised.
And the possibility does exist that there may be a fuse just for trailer lights in the truck, under the dash or hood. A F150 we have has such a setup.

Re: Trailer running lights question
 

Thanks

The truck has an original towing package, so the trailer hitch and the connector plug were there form the manufacturer...which explains the way all the wiring is professionally done, ( neat work and shrink warp on each crimp)

Again, all lights on the truck work. For the towing plug, there's is only power for brakes and blinkers, not for running lights.

Joe

Re: Trailer running lights question
 

Visually check to see if all fuses are good under dash and hood by removeing one by one (so not to get confused). If you have the book (in the glove compartment) on that vehicle it will usually list each fuse location, designation and size.
Don't take it as the gospel that the towing package was installed correctly by professionals. Most of the time dealers will send their vehicles to places like U-Haul and have them installed.
If you run into an impass, just add the T connector and harness and see if that fixes the problem (cheaper and quicker).

Re: Trailer running lights question
 

Bass, I had this problem with my Jeep. With every other vehicle my park lights worked but brake and blinkers did not. I hated that crap. Now with my Yukon, everything works and I'm happy.

Sounds like a similar type of problem. I wish I knew what to tell you. Sounds like Tsub knows a little about how it all works. ;)

Re: Trailer running lights question
 

I can get into a whole speil of what it can be and still not cover the problem, but I'll throw some at you:
The primary cause of all trailer light *malfunctions is the lack (or damage) of a ground, the negative wire, (the black one on the battery) the white one at the trailer light wire harness, what ever color the manufacturer deemed correct in the wireing harness for that particular model that year. This is not to say you can derive a ground from the frame or metal part of a vehicle on newer vehicles, usually it must go thru the wire harness so as to not create other problems in the vehicle, especially ones with a body computer.

Re: Trailer running lights question
 

The green wire is the right blinker and brake light.
The yellow wire is the left blinker and brake light.
The brown wire is the running lights.
The white wire is the ground.
The fact that it works on the Tahoe was a quick analysis (good job), check and see if you get a reading between the white wire and the brown wire (with parking lights on) with a test light (not a meter) closer to the harness away from the plug to see if the plug is damaged.
The fact that the truck had wires spliced could be the whole problem also. I had one that the lights would occasionally not work until I got under the truck and wrapped my hand around the wire connections and twisted.

Re: Trailer running lights question
 

Thanks

I had a light tester at the end terminal and determined that there is no power at all coming from the wires, the terminal plug is fine, I wonder if there's an additional fuse for the running lights alone, normally one fuse covers the whole circuit right?

I need to spend more time under that truck and follow the logical path and your leads with the color code.


Gotta love all this agravation/chalange.(insert head banger HERE) >:(


Thanks guys

Joe

Re: Trailer running lights question
 

Reread this thread. I don't know about newer Dodge (I'm partial to them), but ("96 & newer) Ford does have a fuse just for the running lights under the dash with the rest of the fuses.
Those wire colors are only for the pigtail to the trailer lights,truck wire colors will not corresponde to that.

Re: Trailer running lights question
 

99 Ford F150 had fuse for trailer harness under hood in a small fuse box, Driver side close to firewall away from the big fuse box under the hood.

Had 3 fuse boxes in that truck!! so confusing!!

Re: Trailer running lights question
 

you may have answered this, but did you test without the trailer hooked up. just a test light to the female plug coming off the truck. i have a 95 dodge and will go look at something if you need me to.

Re: Trailer running lights question
 

I have checked (with a 12 V tester) the terminal connections at the round plug, no juice for the running lights. It has to be a #$%&^ fuse .

I have a hard time believing that I have a broken connection or it was wired wrong!!

Thanks

Joe

Re: Trailer running lights question
 

Do the book in the glove box thing.
If not pull and check all fuses one by one.
If no problems add new T connection and harness.

Re: Trailer running lights question
 

Woooooaaahhh. This is not a 4 wire connection? Is this a round 7 wire plug?

Re: Trailer running lights question
 

I have the same plug and they sell an adapter to plug right in for your 4 or 5 wire trailer plug.

When testibng the wires in the round plug make sure you are testing the right side for tail lights, the plugn on truck is in reverse!I have made this mistake before!! :-[
http://syncboard.com/albums/album03/trailer_light.jpg

Re: Trailer running lights question
 

Trying to make this look like the 7 wire plug for Mopar and most others.
Imagine that the notch in the plug is up and you got 6 terminals around the perimeter and one in the center top.

* * * * * * * * * * * * * * * * * notch

* * * * * * * * * * * * * * * 3 * * * * * * 4
* * * * * * * * * * * * *
* * * * * * * * * * * * * 5 * * * * 7 * * * * *6

* * * * * * * * * * * * * * * 1 * * * * * * 2

1 Ground (common)
2 Electric brake
3 Tail & license plate
4 Battery (aux 12v)
5 Left turn & stop
6 Right turn & stop
7 Bach-up lights

Re: Trailer running lights question
 

MJ is giving you the same thing but in reverse. Depending on which end of the plug you're on.

Re: Trailer running lights question
 

Yes mine is the truck yours is the trailer

Re: Trailer running lights question
 

Thanks MJ, it would have taken me checking it to find out.

Re: Trailer running lights question
 

Yeah Bass, if it ain't a 4 wire flat, don't pay no attention to the color code I gave you.

Re: Trailer running lights question
 

Bass,

Something similar happened to me on my 06 Dodge Durango. *I had a guy install a new set of trailer lights on my trailer and when he finished, they didn't work. *I seem to remember something happening intermittently, and then nothing at all. *He ran a circuit tester at the hitch and there was no current. *He swore to me that something was wrong with my factory installed hitch and wiring. *I didn't know any better and had never used the hitch till that day. *So, I took him on his word. *Anyway, I took it back to the dealer and they had to run a complete check to finally discover it was a blown fuse *>:( *Cost me $100 for them to figure that out *>:( *The guy blew the fuse installing the lights!

Sooo, check and recheck all them fuses buddy.

Re: Trailer running lights question
 

Thanks y’all, I think I just solved the problem, my wife just dropped the owner manual.

Tsubaki give me a excelent lead...

On page 136 of my owner’s manual:

D’OH, no wonder why I could find a blown fuse, it ain't a frigging fuse its a flasher whatever that is a relay? ???… I”ll look in the glove compartment tomorrow night.

Re: Trailer running lights question
 

I hate to tell you, but the flasher only deals with the turn signals and 4 ways.

Re: Trailer running lights question
 

Raccoon shift is great for this kind of reading:

Page 133 on the owner’s manual

Page 196
Electric power distribution center

This is it guys, it pays of to read the book FIRST. The fact that I couldn’t find a blown fuse and my 7 to 4 prong connector is partially smashed, it threw me of track until I referred to you guys. Thanks you very much for helping me troubleshooting this problem.

(Another satisfied costumer) ;D

Joe

Re: Trailer running lights question
 

Good, but don't get in the habit of reading the instructions first. All males have a reputation to up-keep (well maybe not stinky).

Re: Trailer running lights question
 

Congrats!!

Re: Trailer running lights question
 

MY Ford Explorer has a factory installed harness and it has seperate fuses for the left, right, and I think one other but cannot remember. So if you have your manual give it a check. I had problems with my gight side blinker and breaks and after doing allot of tracing of wires I found out that the fuse was blown.