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Discussion Starter #1
I've never had trouble on my 2011 with wiring at all, however yesterday i went to unplug my trailer and noticed only some of the lights were working on the trailer and the plug into the truck was VERY HOT to the touch. I've determined that the trailer is not the issue as i hooked it up to another vehicle and all is well and functions fine. I've also noticed that when i hooked a different trailer up to my truck, the lights flickered. The hot harness was the same whether or not i was using the 7/4 adapter or just going straight to the flat 4 plug on the truck.

Where do i start trouble shooting this? potentially a bad ground? where is the ground for the truck plug?
 

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Heat in a circuit will be at the highest at the point where resistance is present. Is your truck equipped with a factory trailer tow harness?

I usually find resistance anywhere moisture can enter a harness. This happens at connectors with a bad weather seal or modified/patched harnesses that were put together or repaired improperly and the occasional factory component that just failed to perform. Usually a stock harness and connector with no modifications or damage rarely fails.

To answer your question the trailer ground should be on the left frame rail near the very rear - usually by the opening for the fuel filler hose unless it has been moved. A bad ground really wont cause heat. I would disconnect any connector back there and inspect for corrosion and or heat damage and go from there.
 

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Discussion Starter #3
Heat in a circuit will be at the highest at the point where resistance is present. Is your truck equipped with a factory trailer tow harness?

I usually find resistance anywhere moisture can enter a harness. This happens at connectors with a bad weather seal or modified/patched harnesses that were put together or repaired improperly and the occasional factory component that just failed to perform. Usually a stock harness and connector with no modifications or damage rarely fails.

To answer your question the trailer ground should be on the left frame rail near the very rear - usually by the opening for the fuel filler hose unless it has been moved. A bad ground really wont cause heat. I would disconnect any connector back there and inspect for corrosion and or heat damage and go from there.
Thanks for the reply ford_doctor. I have the factory tow harness setup and have not made any modifications. I don't believe a fuse would be blown as i'm getting partial signal, so my guess is i have some sort of moisture or corrosion where the harness connects. I will have to start working my way backwards tomorrow from the back of the truck. On my old 2002, i had the whole plug fail on me and had to replace it, so wouldn't be surprised. With the high water we have recently had here in Houston, I'm not so sure i didn't get water somewhere.

If i want to use a volt meter to test whether or not something is bad, would i be doing a resistance test on each pin (with the other to a good ground on the truck) and looking for any wacky values?
 

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I think you are on the right track. Since it is stock there should be two connections you could easily access and disconnect for inspection. The trailer connector itself has the harness connecting to the back and then back on the frame is the second connection either on the left frame rail or secured to the rear cross member depending on the type and configuration of your Super Duty. According to the wiring diagram some trucks have the harness coming straight back right to the trailer connector. From there the harness heads to the front of the truck and not likely to have any issues. The actual trailer connector is the most suspect in my opinion as it gets the wear and tear and exposure. If this turns out to be true the connector itself is available from your dealer.

Hope you are keeping safe and dry there in Houston! Pray that Irma does not decide to head toward Texas!!!
 

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Discussion Starter #5
well, tried to tear into this a little more this evening and found myself nothing but frustrated. i tried using my volt meter and at one point was getting a positive 12v reading on the running lights, then wasn't able to replicate it. when i did a impedance test on the ground wire, i came up with nothing, so i guess that means the ground is good. certainly seems like there might be an issue in the plug itself, so i think i'll try replacing the plug at the back tomorrow. hate to throw parts at it, but the fact that i got an inconsistent reading makes me think this would be a good place to start.

further thoughts?
 

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Not trying to be smart here but are you familiar with using a volt/ohm meter?

When you did the test on the ground did you get nothing or did you get 0 ohms? There is a difference. If you got nothing then there is a problem with the ground, if you got 0 ohms then the ground is good.

Also make sure where you are grounding the meter at is a good ground. I have ran a extra wire from the negative post of the battery to the back of a truck just so that I know that I have a good ground at times
 

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Look up your truck's wiring here:
Search Wiring Diagrams

I think this might be the diagram:
http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=878514

But your signature doesn't say WHICH options the truck has - it can't have them all because some of them are replacements for other options. You have to actually list each feature on the truck for us to know what you've got. Even though many of the detail codes are for older trucks, most of this diagram's caption applies to your truck.


https://www.supermotors.net/registry/media/72354 (for phone apps)



When current is flowing (the circuit is ON and something is happening), resistance causes a voltage drop. Current flowing through resistance causes heat. So a digital multimeter (DMM) can be used to measure either resistance OR voltage drop. A simple wire (conductor) should have NO resistance (nearly zero, but certainly <5 Ohms) and NO voltage drop from one end to the other (assuming it's large enough to carry the current passing through it). Same for a CLOSED switch or a connector's terminal pins (which are pieces of metal touching). If you measure from the Wh trailer wire to the Wh truck wire with the connector fully-inserted, you should find ~0 Ohms and ~0 VDC (with everything that uses 12V on the trailer turned on, including a weak/discharged battery). If you find >5 Ohms resistance, &/or >0.2 VDC drop, the Wh connector terminals are dirty. Same for each of the other wires, but try to turn everything OFF before measuring resistance (pull fuses or relays if necessary/possible) because stray voltage on the circuits can interfere with the Ohmmeter's accuracy. To measure voltage, try to maximize the current flowing (turn everything ON).

DEPOWER the connector (particularly the truck side; not as critical on the trailer side) and clean them. A Dremel with a straight brass wire brush would be best, but heavy corrosion might require the steel version. Once they're all clean, apply ELECTRICAL grease (NOT dielectric, conductive, thermal, chassis, anti-seize, or any other) to each terminal in each connector to keep them that way longer.


https://www.supermotors.net/registry/media/825375
 

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Discussion Starter #8
Not trying to be smart here but are you familiar with using a volt/ohm meter?

When you did the test on the ground did you get nothing or did you get 0 ohms? There is a difference. If you got nothing then there is a problem with the ground, if you got 0 ohms then the ground is good.

Also make sure where you are grounding the meter at is a good ground. I have ran a extra wire from the negative post of the battery to the back of a truck just so that I know that I have a good ground at times
No offense taken at all. Admittedly, i don't use the volt meter a lot, so i'm not an expert. I kept turning the resistance level down to get a good reading (like 200). No matter what ohm setting i had it on, it just kept reading 1+. I might need to do what you did and run a ground from my battery like you did to endure I'm getting a good ground. I had been probing different spots/bolts along the frame at the rear thinking that would help.
 

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Have you zeroed the meter when trying to read the resistance?

If not touch both meter leads together and the reading should be 0 if not there is usually a thumb dial of some kind that you can turn up or down until it does read 0. Also on the volts I had a friend that had a meter that had a broken test lead that would give him bogus readings. You can test it by just checking the battery voltage to see if you get 12-13 volts on your truck battery. This was on a cheap meter from Harbor Freight but can happen to any of them.
 

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A weak battery inside the meter will also give confusing readings. If you don't use it often, change the battery.
 
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