2007 Expedition trailer wiring

[jd-53e]

Just picked up an 07 XLT with the factory flat 4 wiring and plug under the bumper. There is a fifth, blue wire labeled "electric brake" that is taped to the harness and connected to nothing. The fuse and the relay are not in the fuse box, but that's not a problem. The standard square gray connector for the brake controller is under the dash just behind the OBD port. I converted my '93 F-150 and my '00 Expy with ease, but this 07 isn't like the others and none of the after-market kits have an '07 variant. Anyone coverted a flat 4 to 7-wire (to include electric brakes, 12v power, and back up lights)? I hate to break out the wire cutters and electrical tape so early in it's life...

 

[AvroAero]

I dont think its possible. I'm guessing the HD towing package includes the 7 wire harness?

 

[jd-53e]

Unfortunately, the '07 I bought did not have the 536 (HD towing) package; just the basic 4-wire. This deal was just too good to pass up despite it's 4-wire limitation.

BTW, the Arrow is awesome. What an outstanding, legendary effort!

 

[AvroAero]

I agree!

I can give ya a hand here, either you go to a dealer and pay fairly hefty for them to do it, or I can give ya some schematics for it and you go to work. Unfortunately theres just not enough to work with to make a 4 to a 7 pin. It's like trying to make a standalone turn signal. (on a trailer that is)

 

[chevy24d]

JD - exactly the same problem for me too. I crawled under the truck and can't see where the wiring harness (4 wire harness w/brake controller wire) enters the floor board - if it even does.

Does anyone know how hard it would be to install the 7 pin harness?

In my scenario all I need is the 4 pin and a reverse light wire. Is there an easy way to get access to the reverse light wire?

Thanks,

Mark

 

[jd-53e]

Thanks AvroAero! If you have the schematics, I'd cetainly appreciate a copy! I'm not a big fan of others working on my vehicles and the more I look into this issue, the more I'm convinced this 4- to 7-wire conversion is going to require me running the necessary wires to the bumper.

I finally broke down and went to the parts department at the local Ford dealer. They claim the wiring harness is the same for both setups! Their computer lists only two wiring harnesses for the '07s; one for the regular frame and another for the extended. If someone else has an '07 Expedition with the 536 HD towing package, look under the hood at the left fender well. That's where the harness begins. If the label on the harness is visible, could you post the part number??? I'd like to compare that number against the one on my wiring harness.

Mark: I too traced the wiring looking for a place to tap for a back up light. The harness on my Expedition starts, as I mentioned above, under the hood at the left front fender. It runs back along the frame to the flat four plug on the bumper (there are a few stub out plugs along the way). There is no external wiring for the tail lights that I can find. If you need the reverse light to disable a surge brake for backing down the boat ramp, the existing blue brake controller wire may work. Check other posts, here and elsewhere.

 

[chuck s]

No need to mess with the complete wiring harness that I can see. You can get a 7-pole Bargman kit at just about any RV dealer for maybe $25.

As you note, you already have 5 wires back there, including electric brakes (that blue wire). The other two wires are backup lights (center pole) and 12v "trailer battery charge." It's not worth rewiring the truck to get these as far as I'm concerned. Few trailers have backup lights and trailer battery charge is at most a trickle (under one amp) charge anyway.

I spent the extra $300 on the HD Trailer Tow option. Got the wiring and 9000 pounds maximum towing capacity, up from 6000.

Tow relay/fuse box fully populated. Let me know if any other photos will help.

-- Chuck

 

[Toddski]

Originally posted by chuck s
No need to mess with the complete wiring harness that I can see. You can get a 7-pole Bargman kit at just about any RV dealer for maybe $25.

As you note, you already have 5 wires back there, including electric brakes (that blue wire). The other two wires are backup lights (center pole) and 12v "trailer battery charge." It's not worth rewiring the truck to get these as far as I'm concerned. Few trailers have backup lights and trailer battery charge is at most a trickle (under one amp) charge anyway.

I spent the extra $300 on the HD Trailer Tow option. Got the wiring and 9000 pounds maximum towing capacity, up from 6000.

Tow relay/fuse box fully populated. Let me know if any other photos will help.

-- Chuck

Good info Chuck.

I'm new to the forum. I just purchased a 2005 Expedition.
Are you the same Chuck S that owned a Jayco Kiwi?

 

[chevy24d]

chuck - thanks for the pics. to my knoledge the four wires are probobly as follows;
left turn
right turn
running light
common

I don't think there is a reverse wire. I want this to activate my reverse lockout solenoid automatically.

I will double check the wires this weekend.

thanks

mark

 

[AvroAero]

Nuts, the program I use doesn't have the wiring diagrams for the 07s. Sorry dude.

 

[jd-53e]

AvroAero, Chuck,

Thanks for the input. Sorry you don't have the schematics and I did see the photos of Chuck's '07 on a different site; nice ride and very useful pics of the fuse and relay. And yes, I should have opted for the HD towing package, but the deal was too good to pass up.

Chuck, any chance you could find and post the part number of the wiring harness on your '07?

I do need the back up lights and 12v power. I tow a pop up camper and the back up lights come in very handy backing into a camping spot at night and the 12v supply, despite its meager amperage, supplies enough power to suit my needs.

I finally dissected the wire bundle about two feet upstream from the 4-wire plug. Sure enough, there were only five wires. The standard 4 plus the blue brake wire.

I guess it's time to break out the wire cutter, electrical tape, and soldering gun (crimped connections are for those who enjoy electrical malfunctions). Hopefully someone will come up with a better solution before I start tearing apart my new Expedition this weekend!

Thanks to all,

JD

 

[AvroAero]

Guess you have no choice, buy an 08!

 

[chevy24d]

Originally posted by jd-53e
AvroAero, Chuck,

......Chuck, any chance you could find and post the part number of the wiring harness on your '07?
JD

JD - I think when I was reading the owners manual and it actually had the part number of the harness in the towing section. (I know it sounds strange) I am on a biz trip so I don't have access to see if my mind was playing tricks on me or the p/n is really there. Look at it just in case.

Edit -just found this on the download from ford:

Trailer towing (optionally equipped trailer tow package):
The optional trailer tow package includes heavy duty trailer tow wiring.
Both a Class I (4-pin) and IV (7-pin) trailer electrical connector are
provided. Under the instrument panel a electrical connector is provided
for a customer supplied aftermarket electronic brake controller. For
installing a customer supplied electronic brake controller, a electrical
jumper harness and trailer tow electrical instructions are included with
the optional trailer tow package.
The kit containing a electrical jumper and trailer tow electrical
instructions may be purchased from any authorized dealer (Part number
4L1Z-14A348-AA)
Note: Before towing a trailer, make sure the trailer brakes (if equipped)
and lamps are properly connected and functional. Electronic trailer
brakes (if equipped) refer to the instructions provided by the
aftermarket electronic brake controller manufacture for determining
trailer brake functionality.
2007 Expedition

Not sure this is what you really wanted....

Mark

 

[chuck s]

I think there's enough information here to wire the stuff you're missing, assuming the power distribution box sitting on top of the radiator is the same.

You'll have to check to see if there's power to the missing box inputs. If so you just need to run the backup and trailer battery charge wires to the rear bumper and connect to the Bargman.

Click on the photos, you can blow them larger than your screen, they're thumbnails.

-- Chuck

 

[chevy24d]

Chuck - Thanks for the schematics. I think they will me help figure out what is next.

Mark

 

[chuck s]

I think the key is determining if there's power to the relays. The wiring harness in that area is a good inch in diameter but all the markings are well hidden and where the other end goes is a mystery.

The HD towing package is the wiring and larger engine and transmission radiators. I don't know Ford's practice but a separate wiring harness to get just two wires to the rear bumper is probably not cost effective from a manufacturing standpoint and you may have all the wires you need, just have to search for them. Maybe.

Backup lights can be tapped in at the rear bumper.

Trailer battery charge is next to useless because the charge rate drops to less than an amp after a few minutes. The voltage regulator in the truck only lets the voltage get high enough to charge the truck battery and the voltage drop thru the wiring to the trailer drops it even further. I've measured this charge at the the trailer battery and no effective charging is occurring, just battery maintenance. The little Group 24 battery on most camper tongues only has about 55 useful amp hours (the 80 amp hour label includes volts below 11) and at under an amp would take 100 hours to fully charge as the charge rate gets even lower than an amp as the battery approaches full charge.

-- Chuck

 

[Tom Nugler]

Hey JD. Before you break out the soldering iron take a look at the self sealing, heat shrink connectors at one of the better auto parts stores. We have been using these for over ten years at our shop with great success. If you don't like to crip at least use heat shrink tubing. Tape still gives out after a while.
Used them on my old E-150 when I upgraded to 7 pin to haul around my old Airstream. After 8 years the plug crapped out before the connections.
The van also got a pair of 10 gauge wires and a new relay from the battery to the plug. I think I willl add this to to the new TV this summer.
Got a controller? Put a Tekonsha Prodegy in the Expy. Excellent unit. I used the adapter from Tenkosha and it worked great. 07, don't know. Came with the generic plug and plenty of wire though.

Tom.

 

[chuck s]

Just spend the extra 10 bucks and get the Prodigy (or P3) Ford cable. Makes the brake controller Plug n' Play.

This is the P3:

-- Chuck

 

[chevy24d]

Originally posted by chuck s
........Backup lights can be tapped in at the rear bumper.
-- Chuck

Chuck - where did you find the back-up light wire?

BTW for me I don't need the 7 pin as I have surge brakes...

Thanks again - Mark

 

[chuck s]

If you have the towing package the wire is already there.

The center pole of the 7-pole connector on the rear bumper is backup lights -- technically that pole is "undefined" or "auxillary" but Ford connects it to the backup light circuit. Was like this on my Explorer too.

On my '02 Coleman Bayside popup there was no connector on the trailer's umbilical cord so I had to run another wire thru the harness. Mounted automobile fog lights on the rear bumper for backup lights. One wire. Ground via the frame.

On my '06 Rockwood Roo 23SS the wiring is already in the cable, but capped at the junction box. YELLOW wire in the 7-wire cable is backup lights. Same drill with fog lights on the rear bumper.

-- Chuck