Running Lights truck fuse keeps blowing

[Pongo]

I'm blowing fuses on my 2018 F250 for the 2017 International 27FB running lights. The stock rear view camera is also wired into the running lights at the back of the trailer, so the camera loses power as well.

I first noticed the problem shortly after having to turn around on a very narrow road, which necessitated a very sharp turnaround. I'm not sure that this had anything to do with the issue, but raise the point just in case. At first I thought the issue was excessive dielectric grease, so cleaned things up & replaced the fuse. It ran for an hour until I hit rain and blew again. this happened once or twice more, but now the fuse blows instantly.

The truck wiring is fine; verified by the ford dealer and by swapping vehicals. I've replaced the 7-pin connector & cable, which terminates inside a black terminal box located in the coach's front storage compartment. I've also disconnected the coach wiring harness connector, located under the curbside seat beside the dining table and still blow the fuse, which would indicate that the problem is towards the front half of the trailer.

Having spent way too much time crawling around upside down in the front storage compartment, I'd sure love someone to tell me what I'm missing.

Thx
Mark

[GCinSC2]

Mark,

Interesting, new cable, plug, swapped vehicles etc.

I'm curious about repeating testing with the 7 way cable lighting L-R-Park circuits disconnected from the trailer at the junction box.

Connect to truck and test all controllable 7 way circuits, light and brakes. Fuse OK?

Connect ONE light circuit at a time, repeat test. Fuse OK?

Optional testing for trailer isolated from TV. At the junction box, find the positive charge line and use a fused jumper to go from + to each light circuit one at a time. Jumper fuse OK?

Did you replace the cable from the plug all the way to the junction box in the front of the trailer?

What really has me scratching is the problem started after a tight turn and continued after cable and plug R&R.

What happened when you used a different TV?

Gary

[Pongo]

Originally Posted by GCinSC2

Mark,

Interesting, new cable, plug, swapped vehicles etc.

I'm curious about repeating testing with the 7 way cable lighting L-R-Park circuits disconnected from the trailer at the junction box.

Connect to truck and test all controllable 7 way circuits, light and brakes. Fuse OK?

Connect ONE light circuit at a time, repeat test. Fuse OK?

Optional testing for trailer isolated from TV. At the junction box, find the positive charge line and use a fused jumper to go from + to each light circuit one at a time. Jumper fuse OK?

Did you replace the cable from the plug all the way to the junction box in the front of the trailer?

What really has me scratching is the problem started after a tight turn and continued after cable and plug R&R.

What happened when you used a different TV?

Gary

Thx Gary,

Turn signals, break lights & breaks all work. The running lights are on a separate 7-pin wire. Yes, I did replace the 7-pin connector all the way to the terminal box in the front storage compartment. There is only a single wire tied to the 7-pin cable in the junction/terminal box for the running lights, which I assume runs into a wiring harness. I've not been able to dig into this as of yet. As to the sharp turnaround being a root cause, I'm scratching my head as well. That's why I'd replaced the entire 7-pin connector & cable.

The saga continues ...

Fuse #98 blows in the truck - no others do.

I

[steve46]

I have had this problem and here is what I discovered: one of the clearance/running lights on the front was the spot that was repeatedly blowing the fuse in the tow vehicle. Whether it matters or not, my Airstream is a 1976 Trade Wind and the tow vehicle is a 2012 GMC Sierra. When I removed the amber lens I discovered that the bulb had come loose and caused the power “blade” to touch the ground thus shorting the circuit and blowing the fuse. I’d suggest checking each of those running lights, front and rear, to see if this might be happening to you. Hopefully this is your situation as it is a fairly easy fix to an extremely frustrating circumstance. On my Airstream the taillights (but not the brake lights) are on this same circuit therefore while it may be possible to drive and tow during the daylight hours if that fuse is blown, nighttime towing is not safely possible. I hope this helps.

[uncle_bob]

Hi

Best guess: You tapped a running light on that tight turn. As noted above, one of the contacts on that light now almost touches ground. Bump down the road long enough and it makes contact. It could be a loose wire nut (normally behind the light fixtures) or some weird chunk of debris in the same general area.

Bob

[ROBERT CROSS]

Dad the ???? isn't working now!!!!!
"Well, what was the last thing you fixed?"

Just a guess...but I would ck the wiring for the camera first.
But thats just because of Dad.

Bob
🇺🇸

[GCinSC2]

Ok just to pin it down a bit what does fuse 98 power?

[Pongo]

Originally Posted by GCinSC2

Ok just to pin it down a bit what does fuse 98 power?

Fuze 98 is "running lights"

[Rich W]

Originally Posted by ROBERT CROSS

Dad the ???? isn't working now!!!!!
"Well, what was the last thing you fixed?"

Just a guess...but I would ck the wiring for the camera first.
But thats just because of Dad.

Bob
🇺🇸

Well Amen and hallelujah! Someone else knows the motto: "Last thing fixed is the first thing broken".

[guskmg]

I had the same problem a few years ago and it turned out to be a short in the pigtail caused by pinching is a tight turn. It caused a low grade short and eventually did a lot of electrical damage.
guskmg

[xyzabe]

Had a similar issue with a boat trailer. Intermittent grounding issue kept blowing fuses. Check where the 7 pin grounds on the trailer.

[fwjumper]

led lights or incandescent?

[LiveStreamn]

Had a very similar issue on our 2019 19’ Tommy Bahama. I did everything you did. Fuse would blow immediately or randomly on the road. Weeks at the dealer and they had it. Drive two hours to pick it up and an hour into my trip home…yep, it blew. Next trip was to Colonial where they started pulling interior panels and finally found a single wire that had rubbed about an 8th of an inch raw. So every now and then it would touch something and cause the short.