2007 Expedition trailer wiring

[chevy24d]

Originally posted by tk1971
One more thing for anyone wanting to do this, but didn't go through the entire thread. The non-HD tow Expies have the same fuse box under the hood. Putting a 30amp fuse and relay in place will get a fused/relay-controlled 12V to the hitch wiring harness connector up to the engine compartment. You will have to run a 10 gauge wire to the back of the vehicle to get the trailer charging 12V back there.

There is also a 15amp fused reverse 12V at the fuse box that ends in the engine compartment harness. There really is no need to pull this one, as you can get a reverse 12V by tapping one of the reverse lights at the back of the vehicle. But since I was pulling the 12V, putting another wire in the flexible wiring loom is really no work at all.tk

I am thinking of using the blue e-brake wire under the dash. I want to connect this reverse light circuit you mentioned under the hood, to this harness under the dash. Then, at the trailer hitch I will wire the blue wire to the reverse light circuit as I do not have or need electric brakes. I will also connect my new back up camera power lead to this. I am hesitant to tie off my existing reverse light wire because I checked it out today and the wire size was extremely small. I know the camera is low power and the reverse solenoid is less than an amp, but if I can use a separate circuit it will be better. I hope you can tell me how to pick up this fused wire so I can bring it into the plug under the dash.

Thanks for all your help. Mark

BTW - I am using the 4 to 6/4 combo unit and yes, my friend works at a sheet metal shop and we went there today to make my fancy bracket!

 

[chuck s]

Don't mess with the blue electric brake wire, please. It's wired to the interface connector under the dash and you (or the next owner) may use electric brakes, they're superior to 1930s technology surge brakes. If you have a boat trailer the newer electric-hydralic brakes are super!

Backup lights on a trailer are very nice but lower priority than brakes.

-- Chuck

 

[tk1971]

I have a backup camera and a Wolo backup horn tapped to my driver side reverse light wires (done before I thought about going to the 7pin hitch connector). That shouldn't be a problem since it is in use only when I go reverse (which is not too often) and those are low wattage devices, so I have no plans to re-do it and connect it to the 7 pin connections I just put in.

But, when I put together the 7pin connector, I did want to put a halogen backup light under the bumper, so I am tapping the newly pulled 7pin's reverse wire to turn on a relay, which is also tapped to the fused/relayed 12V I pulled from the front of the hood for power. This lets me pull the 55watts from the 10gauge wire for the 12v when I go in reverse. I then wrapped the relay up with electrical tape and zip tied the relay above the spare tire.

I have a picture earlier in this thread showing the harness under the hood and which wires to cut to get the 30-amp-fused/relayed 12V and the 15-amp-fused reverse. Of course, if you have access to the male pins, you can just put the pins into the mating male harness and avoid cutting. The 30A 12V from the relay is Orange and about 10gauge in size and the 15A reverse is Gray with a Black stripe, and is located almost right under the 30A orange on the harness.

 

[chevy24d]

Originally posted by chuck s
Don't mess with the blue electric brake wire, please. It's wired to the interface connector under the dash and you (or the next owner) may use electric brakes, they're superior to 1930s technology surge brakes. If you have a boat trailer the newer electric-hydraulic brakes are super! Backup lights on a trailer are very nice but lower priority than brakes.
-- Chuck

Chuck - I have $1000 invested in my brakes which work great. I know it is easy to spend other peoples money... I also would never consider back-up lights on my trailer - I have an electric solenoid on my surge brake so when I go into reverse, the fluid stops from being applied to the brakes and allows backing up the trailer easier. This is a common option with surge brakes.

The blue wire is a neat way to avoid running one new wire to the rear, since Ford was so nice to install this to the connector under the dash for you e-brake guys. It is funny you mention the "next Owner" as I just said to my friend I was tired of worrying about the next guy and I was going to do a professional and safe install for me.

TK - Are you saying that the Grey/back wire comes from the fuse box and goes into the connector where you show it cut? and does it dead end there or does it connect to another wire in the mating harness? Sorry for all the questions.... Thanks

 

[tk1971]

Chevy,

Your statement is correct, the gray/blk wire from the picture contains wires that originate from the fuse box under the hood and ends just right there on the female connector. That's a fused 12V that goes on when the vehicle is put in Reverse.

Unfortunately, it does dead end there in the engine compartment. The mating male connector is the wiring harness that goes all the way back to the vehicle, containing the existing flat 4 wiring. Looking at the male connector, you'll see that the pin to connect to this fused reversed 12V is missing, along with the wire going into the harness. And that's why I cut the wire from the female end of the connector. I then connected it to a 20ft length of 14gauge wire and pulled it to the back of the vehicle.

I did not check whether or not the blue wire goes to the engine compartment. It is to my understanding that it terminates under the dash inside the vehicle. So, with that in mind, if you still want to use it, you would have to make a firewall penetration to connect the gray wire (under the hood) to the blue wire inside the cabin.

I personally would rather pull new wiring than to make a firewall penetration but that's just me.

Good luck.

tk

 

[chevy24d]

TK - Thanks - that helps me alot! I am going to see if there is a entry from the firewall that has a nice grommet already, that may allow me to sneak this wire thru. Now I know what to look for.

BTW I went to the dealer last week and they said the wiring harness is about 160 bucks but they did not have a pic or one in stock so I could not fully understand what I would get.... Oh well

 

[chevy24d]

After looking at the harness TK pointed out, it appears that this harness is the one that can be upgraded. After seeing this now and following it back along the frame, it doesn't seem too hard to replace.

I also think that if I decide not to upgrade the harness, I can sneak a single wire in the boot that the hood release cable goes thru on the firewall, and connect to the blue wire I mentioned above.

Decisions, decisions......

 

[chuck s]

You can connect to the Blue Wire at the under dash connector and not bugger the wiring under there. Should have been a brake controller pigtail with your truck.

You've been thru a lot of trouble to retrofit what's a $350 factory option.

For lurkers: Just order HD trailer tow,

-- Chuck

 

[tk1971]

I'll 2nd this: "Just order HD trailer tow". But only if you get a good deal. Sometimes, a deal comes along that may not have every option that you want, but a good deal is hard to come by.

I paid $19,950 in 2007 for a 2007 XLT with 19,600 miles on it. It did not have the HD tow, but I couldn't pass up that deal.

But for what it's worth, working on cars/trucks is fun and it's my way to unwind after a busy week.

tk

 

[chevy24d]

Originally posted by chuck s
You can connect to the Blue Wire at the under dash connector and not bugger the wiring under there. Should have been a brake controller pigtail with your truck.

You've been thru a lot of trouble to retrofit what's a $350 factory option.

For lurkers: Just order HD trailer tow,-- Chuck

Ditto what TK said - I too enjoy working on cars/boats.

Chcuk - If I bought it new I would definitely get the option!

BTW I agree about using the $10 harness adapter to the brake plug. I have to be careful because one of those wires is hot all the time and the other is hot every time you step on the brake. Since I won't be plugging into a brake controller, these wires will be exposed. I will either have to cap them or remove them from the harness. I may just say forget it and just tie into the blue.

Edit -------
I forgot to mention the real reason I am doing this myself- my wife said "if you spend one more dime on that truck......" I did not get as good of a deal as tk