Running lights intermittently working

[Linnemj]

The running lights are working intermittently when towing. I have brake and turn signals.

Any suggestions on how to troubleshoot this problem?

Thanks!

[TURBS]

Loose connection at truck receptical.
Loose connection at trailer plug.
Loose connection at junction box under trailer if its a tt. In the pin box if it a 5th wheel.
Bad ground on running light circuit.


Turbs

[Linnemj]

Where would I look for the loose ground connection?

Thanks!

[avolnek]

Chances are slim it will be a grounding issue if all the running lights stop working at the same time. Many of the lights will be grounded to the frame, so if there was a ground issue chances are ALL the lights wouldn't work at the same time... (brakes and all)

Just make sure the pins on the truck are making good contact with the receptacles in the plug for the wiring on the 5er. Chances are the pin and recep are loose. Or as turbs said the wiring in the junction box on the back of the pin box for the pig tail to plug into the truck may have a loose wire... Those would be my two best guesses.

[Linnemj]

I have a travel trailer rather than a fifth wheel. I will start with the seven pin connector after identifying which pin is for the running lights.

Thanks

[kz08h5]

Are All the running lights intermittent at the same time or are the lights individually intermittent? I have the latter problem and it appears to be leaking lense covers. Some of the lamp sockets are corroded. As the trailer goes down the road vibration makes them go on and off.

If it is all the running lights check the wiring around the front of the trailer for an open or frayed wire. If the frame is used for ground, it is most likely an issue with the power side for these lights. The 7 pin connector and the junction for the first light are where I would check.

[TURBS]

If you hold plug in hand and face prongs towards you with the alignment bar at 12 oclock the running lights are at 1 o'clock.

As seen in my next post at right.

[TURBS]

Better diagram

[avolnek]

Great picture Turbs! you will also notice the 12v+ and ground pins/holes will be larger than the others... DONT CONFUSE THEM!

[Linnemj]

Here is an update. The trailer lights checked out fine using the technique described in this thread. The truck's seven pin was checked at a dealer under warranty and also was fine. It seems like the female end of the running light plug on the trailer is spread open too far. I used a flat blade screwdriver to pry the two ends closed together. This solved the issue for the moment.

Since the trailer plug is molded there is no way to open it.

Does anyone have any suggestions on how to make the connection better long term besides replacing the entire plug?

Thanks for all of your suggestions!

[Herk7769]

I used this technique to troubleshoot a running light problem.