Running light issue

[jmlocklin]

I have a backup camera that is wired to the running lights on my 2017 Keystone Sprinter. I have been using the lights in the daytime in order to use the camera giving a view of what is behind the trailer. Problem is the running lights went out while leaving a campground. I immediately stopped to make sure I still had the turn signals and brake lights working. They were still working. Any suggestions on what might be the problem. I suppose it could be a fuse, but I cannot find any diagram of what fuse works what. How do I trouble shoot this problem?

[chuckster57]

You need to make sure you have 12VDC at the umbilical cord.

Go here:
https://www.etrailer.com/faq-wiring.aspx

And then with the truck lights turned on, just use aVolt/OHM meter to test for voltage at the truck end. You can also jumper the trailer end to diagnose/rule out the trailer wiring. Before I bought a plug, I used to Jumper the trailer cord all the time.

At the truck you going to test across the ground and running lights. On the trailer you going to jumper power to running lights.

No power at the truck side- probably a fuse in the truck.
No lights when jumpering at the trailer plug- most likely a loose wire.

[JRTJH]

Here's the way I'd approach it:

1. Using a paper clip formed into a "U" shape, jumper between the two pins next to the "index guide" on the trailer end of the umbilical. Those two pins are 12VDC and TRAILER RUNNING LIGHTS. If the running lights work, the trailer is good and your problem is in the tow vehicle. If they don't work, you have a wiring issue in the trailer. (be sure your trailer battery cutoff switch is "ON")

2. If the running lights do work (in the step above), then go to the truck (I think you have a 2016 F150) open the hood and you'll find a "power distribution box". On the 3.5L EcoBoost and 5.0L V8, it is front/center directly behind the radiator. Open that box and you'll find a number of fuses and relays. The trailer running lights are fuse # 34 and # 36. Chances are that one of them is bad. They are 25 amp mini-fuses, commonly found at any hardware or auto supply store.

Your truck owner's manual has the power distribution box layout and fuse diagram listed.

Let us know what you find when you "go looking".... Good Luck !!!

[Tinner12002]

Unrelated, but thanks for the wiring diagram, printed a copy of it to keep in RV packet!

[travelin texans]

What difference would it make if the trailer battery switch is on or off, it has nothing to do with the running lights.
Enquiring minds want to know!

[wiredgeorge]

Do you tail lights work? If so, the problem isn't the 7 pin connection. Suggest you have a look at the connection where you spliced in the wires for the camera as most likely point of failure. After that, the marker lights are likely in series so you will need to check the wire nuts on those, one after the other I guess.

[JRTJH]

What difference would it make if the trailer battery switch is on or off, it has nothing to do with the running lights.
Enquiring minds want to know!

If you're using the 12VDC pin on the umbilical to power the running lights for the test and the battery cutoff switch is between the umbilical and the battery, you won't have 12VDC at the umbilical, so "jumpering" between the two pins on the umbilical wouldn't illuminate the lights. If, however, the battery cutoff switch is not between the battery and the umbilical wiring, it wouldn't matter.

So, rather than try to explain all of that in an already confusing (for someone with little electrical troubleshooting experience) I just suggested that he be sure the battery cutoff switch is on. That would eliminate any "false problems" with not having power at the 12 VDC pin on the umbilical..... Now "enquiring minds know".....

[jmlocklin]

I found that the fuse for the trailer lights in the truck was blown. Will replace the fuse tomorrow and get an extra one so if it happens again I'll know what to do. That leaves the question of why it blew, so there could be a short in the wiring related to the backup camera ???? Not sure if the weather could have been a contributing factor but had a sever storm (wind and rain) during the night before I hooked up the trailer. Had gone about 5 miles before it blew.

Thanks for all the suggestions and the wiring diagram.

[jsmith948]

I found that the fuse for the trailer lights in the truck was blown. Will replace the fuse tomorrow and get an extra one so if it happens again I'll know what to do. That leaves the question of why it blew, so there could be a short in the wiring related to the backup camera ???? Not sure if the weather could have been a contributing factor but had a sever storm (wind and rain) during the night before I hooked up the trailer. Had gone about 5 miles before it blew.

Thanks for all the suggestions and the wiring diagram.

Don't know about your TV, but our Ford has those square fuses ( I think they are called J-case?) and they are rare like hens teeth at the parts stores. Had a similar problem with the running lights on our Cougar. Never did find the fault.

[66joej]

For what it's worth. On our Cougar running lights worked just fine until a screw installed at the factory that was inadvertantly run through the wiring harness rubbed the insulation and resulted in a dead short. Took me many hours of tracing wires to solve.

[hankpage]

Just a thought .... If your trailer does not already have LED running lights, this would be a good time to up-grade. Adding the camera to the circuit may have brought it close to over load and caused the blown fuse. If self resetting circuit breakers are available to replace that fuse, they are another alternative. Just thinking out loud, Hank

[JRTJH]

If you're considering changing incandescent running lights to LED's. These are the cheapest, brightest (for the money) LED's that I've found. They have been on my Cougar for over a year and no problems yet. At the price, 49 cents each, they are hard to beat. Just be sure to put some silicone di-electric grease (available at any auto parts store) on the contacts when you install them.

https://www.amazon.com/gp/product/B00GZGM8BW/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1