Fuse 10 & Tail Light Troubles

[IceKing]

Howdy everyone. I have had my van for about a year now and I love it. 2006 E250 5.2L that I use as a tow rig for my track car and a weekend camper. It is currently giving me a headache with the tail lights. Recently I noticed that my tail lights were out on my way back from the track. Turn signals and brake lights work fine, but the tail lights were not functioning. I am having a **** of a time figuring it out. I feel like I have to re-learn wiring stuff every time it comes up, seems to never stick.

Details:
- I installed a tow wiring kit which is a 4 pin harness that then connects to a 7 pin. The 7 pin is wired to a brake controller. All from E-Trailer
- When I plug the 4 pin into the 7 pin, fuse 10 pops immediately. Seems like the culprit but the fuse has popped when the 7 pin is isolated from it.
- I used the 4 pin to the trailer bypassing the 7 pin and it popped before I was out of the lot.
- The fuse does not pop immediately when the 7 pin is disconnected. How long it takes to pop varies.
- The right pig tail had a loose-ish brown wire that when jiggled it cause the light to flicker.

Attempts So Far:
- Replaced tail light bulbs, third brake light bulbs, license plate bulb.
- Replaced the right pig tail with a new one.
- Multimeter used to confirm 12 volts are getting to the factory pigtail. Red probe on brown pin, black probe on black pin. 13.5 volts present.
- Same with the orange wire for the turn signals. 13 volts present.
- Tried a 30 amp fuse, no luck.
-There are no continuity/voltage problems with the 4 pin harness.
- There are no continuity problems with the 4 pin wiring that is in the 7 pin plug.
- I unwrapped a few sections of the factory harness but found nothing strange. Have not unwrapped it all yet.

Something I find odd.
With bulbs removed, and third brake light unplugged, I get continuity from all three wires of the pig tail with a bare metal patch of the body. I thought that would only happen with the ground wire. This leads me to believe there is a few bare wires touching the body.

I would really like to get this resolved before I start to figure out installing walls and especially before my next track day. Any ideas will be immensely appreciated.

 

[1der]

Any issues before the Tow Wiring kit was installed?

 

[IceKing]

Unfortunately I installed it almost immediately after getting the van so I can’t really say.

 

[kbeefy]

Is it wired to the factory 4 pin or spliced into the taillight wiring?

Just to clarify, does it blow when you plug in the 4 - 7 wire adapter with the trailer disconnected?
Does it work without the trailer connected?

Something I find odd.
With bulbs removed, and third brake light unplugged, I get continuity from all three wires of the pig tail with a bare metal patch of the body. I thought that would only happen with the ground wire. This leads me to believe there is a few bare wires touching the body.

When you say pigtail, do you mean the L/R taillight connector/pigtail? Hi, low and ground all have continuity to ground? How many ohms? Does it do that with the 7 wire unplugged?


Lastly, pics of track car please.

 

[1der]

If you want to take jaunt down to San Francisco, I can have a look at it.

 

[IceKing]

It is "spliced" into tail light wiring. My van did not have any of the factory towing equipment.

4 pin wiring

https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Ford/Van/2006/C56020.html?vehicleid=200620061172423

The brake controller and harness

https://www.etrailer.com/Trailer-Brake-Controller/Tekonsha/90885.html#exp-productdetails=.related-products

https://www.etrailer.com/Accessories-and-Parts/Tekonsha/3035-P.html

The 7 pin

https://www.etrailer.com/Trailer-Wiring/CURT/C57672.html

So the 4 pin wiring splices the tail lights. Plugs into the 7 pin which has receptacles on the front for using 4 pin or 7 pin. When I plug the 4 pin harness into the 7 pin harness the fuse pops immediately.
So my last trip I didn't bother with the 7 pin at all and just used the 4 pin wiring harness. The fuse popped then as well when hooked up to the trailer. When I have no trailer hooked up the fuse lasts longer but eventually does pop.

Yes the factory wiring connector for the tail light bulb. I replaced the right side with this one since it seemed like the connector was going bad.

Duralast Tail Light Harness 835

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But when I had it installed and was testing everything, the fuse eventually popped. By touching the multimeter probe to the pin in the pigtail and the other to the body I would get the continuity beep. From all three, on both sides. This is without the 4 pin wiring harness connected, which also means the 7 pin is disconnected as well. I don't remember ohm values so I will have to test that again tomorrow.

I will have to retrace my installs of the towing gear and see if I crossed something up. But since the fuse pops without it I am thinking I need to look at the vans harness with more scrutiny.

@1der I might have to make the trip down to you if I don't get this nailed down. I am going to try and do the tedious stuff here and rule out as much as possible before then though.

 

[kbeefy]

Well, I always look to the last thing touched when a new problem arises.
You have a short even with the 4 pin disconnected, so I'd try unplugging those taillight adapter connectors and see when your continuity to ground disappears. Also restore it to the original configuration and see if it's still there. Maybe that pigtail install somehow created a short.

 

[carringb]

Do you have anything attached the to the walls? The harness for the rear lights runs up the B-pillar then along the roof line. So it’s susceptible to screws if panels or cabinets in those areas are installed using screws.

Once that is figured out, I strongly recommend upgrading to a self-powered trailer light adapter, that way a trailer fault won’t wipe out the van’s lights.

 

[IceKing]

So I was able to fiddle with it more today to get continuity numbers. With the two tail light bulbs and the third brake light unplugged, without the four pin harness I got this:
Passenger
Orange wire 39 ohms
Brown wire 13 ohms
Black wire 1 ohms
Driver
Green wire 38 ohms
Brown wire 3 ohms
Black wire 2 ohms

When I have plug in the 4 pin harness and check continuity I get these numbers:
Passenger 4 pin
White .5 ohm
Blue 2 ohm

Driver 4 pin
Brown 1.5 ohm
Yellow 39 ohm

All of these were taken by putting the red probe on the wire pin and the black probe on a hinge bolt free of paint.

I did find that my driver side light harness pigtail has a loose brown wire that interrupts power just like the passenger side. I am going to replace that as well.

Tested again and as soon as I plug the 4 pin into the 7 pin the fuse immediately popped. I double checked my wiring of the electric brake controller to 7 pin. All of that looks to be correct per install instructions. The only thing I can think of is that I used too small of wire gauge. But I used 10 gauge from the front of the van to the back with a 40amp circuit breaker on the battery line.

 

[IceKing]

Do you have anything attached the to the walls? The harness for the rear lights runs up the B-pillar then along the roof line. So it’s susceptible to screws if panels or cabinets in those areas are installed using screws.

Once that is figured out, I strongly recommend upgrading to a self-powered trailer light adapter, that way a trailer fault won’t wipe out the van’s lights.

I do not currently have anything attached to the van that might be messing with the wires.

 

[IceKing]

At this moment I have unplugged the cargo area harness from the two b-pillar plugs.
Testing continuity from the light pigtail to the main harness plug I have 4 ohms when I am probing brown wire and ground wire. Interestingly I don’t have any continuity with the green or orange wires.

Gonna keep peeling the wrapping off of the harness and see what I see

CORRECTION: I am a dumby and left the license plate bulb in place. With the removed I am not getting any continuity problems.
Now when I check the b-pillar connectors I still have 40 ohms from the orange wire to ground, same with green, and 1 ohm from brown wire to ground

 

[doublevan2]

IC -- So - without the license plate bulb - all is good - or same fuse popping ?

 

[IceKing]

I am admitting defeat to the battle of factory wiring grounding issues. I was trying to diagnose a problem of a system I didn’t understand. I unwrapped 75% of the harness that contained the brown wire trying to find a short to ground. After about 8 hours of working on it I realized that there is a relay in the engine bay that it runs to. As soon as that was removed, the grounding ‘issue’ disappeared. Same with the orange and green wires from the tail lights.
Let this be a cautionary tale to anyone with electrical problems. Research the system before wasting SO MUCH TIME.

I swear the fuse pops without the trailer stuff present but I drove the van for a day of errands without any issues. So maybe I have been wrong this whole time. Now I will be re-wrapping the factory harness and putting everything back together so I can focus attention on my non factory tow equipment.

I will win this war.