Running lights

[Shortest Straw]

We just brought our rig back from the dealer today and noticed that the running lights are not working if the pickup is turned off. We have had over the years a 4 horse stock trailer, a couple of flatbeds, and of course 3 rv's that have not done this. Am I missing something? It seems to me they should work on the trailer regardless.

 

[MCTalley]

If the pickup's lights are on, the trailer's running lights should be on, regardless of whether the truck is on or off.

 

[StarryNight]

Our rig's running light are on only if the truck's lights are on (whether the truck is turned on or not)...they will even turn on if the truck is off but the doors are open because the truck's lights are on then.

 

[Shortest Straw]

That is what I am used to. I am handy electrically speaking but I dont even know where to begin looking with this issue....

 

[Bones]

The best thing to do is start with the easy stuff first. Check the truck connection with a 12 volt test light. That will tell you if your truck is supplying power. If that test out good then jumper the pig tail lights and see if they all come on and work your way from there. if you get nothing then open the connection box for the pig tail and test all connections. Make sure you test the pig tail as well to make sure it is good and is not damaged. You could also jumper directly to the pig tail connections to see if they work directly. If you still don't have anything start removing lenses from the lower lights and check each one individually to make sure ground points are still good and that you are getting 12 volts. It will take a lot of time to do this so make sure you do one thing at a time to trace your problem down. Post back if you have any other questions and what you have figured out.

 

[Bob&Patty]

Do you have auto headlights?? If so, maybe the timer has been turned way down. Have you had the TV washed lately?? Were they working with the key on?? If so you do not have a problem with the lights. Maybe pilot error has occurred. Just saying.

 

[EPaulikonis]

X2 with Bones. Problem sounds like you might have a bad relay or blown fuse in the 12V Battery Power hot line on the vehicle. New trailer, so I doubt you'd notice if the "hot" 12V charge line wasn't providing power to the trailer battery.

When the vehicle key is off, power is supplied through the 12V Battery Power circuit only. Best way to confirm is by checking all connections on the truck with the key turned off. Since you're having problems with the marker lights, turn the vehicle lights on during this first step. Even with lights turned on for the vehicle, the only connection that should light up is the 12V Battery Power pin. Now go back and turn the key to the on position and re-check all of the pins on the truck's connection point. The Tail and Running Lights pin should now be hot and I'd expect that your 12V Battery Power line is dead.

Attached a few images to help with diagnostics. Best image I could find was for a 2006 King Ranch, but it clearly shows relay #301 as the hot lead to trailer battery.

 

[StarryNight]

Hey Mike...do you have a Ford, Chevy...? Don's thinking there may be a relay in your truck that prevents the RVs lights coming on when the truck isn't on...to keep battery level from bottoming out.

 

[Shortest Straw]

Hey Mike...do you have a Ford, Chevy...? Don's thinking there may be a relay in your truck that prevents the RVs lights coming on when the truck isn't on...to keep battery level from bottoming out.

We have a Ford. Unfortunately work is keeping me away from trouble shooting so i will have to wait for the weekend.

 

[Shortest Straw]

X2 with Bones. Problem sounds like you might have a bad relay or blown fuse in the 12V Battery Power hot line on the vehicle. New trailer, so I doubt you'd notice if the "hot" 12V charge line wasn't providing power to the trailer battery.

When the vehicle key is off, power is supplied through the 12V Battery Power circuit only. Best way to confirm is by checking all connections on the truck with the key turned off. Since you're having problems with the marker lights, turn the vehicle lights on during this first step. Even with lights turned on for the vehicle, the only connection that should light up is the 12V Battery Power pin. Now go back and turn the key to the on position and re-check all of the pins on the truck's connection point. The Tail and Running Lights pin should now be hot and I'd expect that your 12V Battery Power line is dead.

Attached a few images to help with diagnostics. Best image I could find was for a 2006 King Ranch, but it clearly shows relay #301 as the hot lead to trailer battery.

View attachment 43017 View attachment 43014 View attachment 43016

The fuse is good and I replaced the relay. There is no change. I am getting the light on the test light I have to come on with the park lights on or the blinkers.

 

[Storm1972]

The running lights will be the pin to the left of the top centre on your trucks plug, usually brown colored wire, make sure you have a good ground on your test light , I am dealing with the same issue this morning lol


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[Shortest Straw]

I had a broken ground wire. Problem solved and thank you for the idea.