trailer wiring

Does anyone know how the stock trailer wiring is set up? From the 7 pin connector, is there a plug somewhere by the back bumper, or is it just wires running up to the fuse box?

The reason I ask is because the previous owner of the truck tapped into a bunch of the wires at the 7way to put in other plugs. I think this might be causing me a ground issue (and I never use the other plugs), so I want to replace the 7way, and the wiring. I'm hoping that it's a separate harness that has a plug under the truck that taps into the main harness, similar to the 'T' connectors that they sell for other vehicles that let you add trailer wires without splicing into the vehicles wires.

This isn't exactly what I'm talking about, but it should give you an idea -

Ford Trailer Wiring Kits - 2002-2004 Ford F250 / F350 Super Duty - Trailer Wiring Kit

Let me know what you guys know. If it works like I hope it does, I'm going to call up some junk yards and look for the harness, and a new rear bumper.

Thanks,

- Steve

It has been awhile for me, but I think there is a plug under the truck. I think it is along the driver side frame rail, above the rear axle. I know I have some splices there, so I think that is where it is.

I believe how I found it was to trace the wires from the plug back. Drop the spare tire and craw under.

If I remember more, I'll let you know.

dboyw said:

It has been awhile for me, but I think there is a plug under the truck. I think it is along the driver side frame rail, above the rear axle. I know I have some splices there, so I think that is where it is.

I believe how I found it was to trace the wires from the plug back. Drop the spare tire and craw under.

If I remember more, I'll let you know.

Click to expand...

What he said.

Should be about 12" back from the bumper.

the splices are under the hood.. there are duplicate wires running from the underhood PDC..

for example, here's the diagram for my truck...

There are 2 pigtails at the rear of the truck. The first attaches to the main harness; it's on the dr side inside the frame rail. The 2nd attaches to this pigtail and terminates at the trailer plug.

They are both available at the dealer. The 2nd is available, slightly cheaper, from online trailer parts places (e trailer among others) or rv parts houses.

Very easy to swap our.

Good luck.

Mike

That is what I was hoping. Anyone know if the '08 and up harness has the same plug as my '06? I'd like to switch to the newer style plug so that there are not wires hanging out for the 4-way (which is where the PO spliced in the additional plugs).

Haven't had any luck locating these harnesses... I called the dealer, and he said that he'd need my VIN in order to identify exactly which wire harness I needed... apparently the trailer only wires are not available by themselves.

I've also looked online, but haven't been able to locate what I believe that I am looking for. Anyone have any insight into exactly what I should search for?

TexasA&M said:

Haven't had any luck locating these harnesses... I called the dealer, and he said that he'd need my VIN in order to identify exactly which wire harness I needed... apparently the trailer only wires are not available by themselves.

I've also looked online, but haven't been able to locate what I believe that I am looking for. Anyone have any insight into exactly what I should search for?

Click to expand...

Just my .02 but I can't think of any reason why Ford would change anything for the 4 & 7 pin trailer harness' & plug.

My Ford guy sez the only reason for the VIN #, is for the [length] of a pig-tail.. to a body style.. the pin diagram is on the 7 pin flip-lid.

Or am I missing something here

Joe

That's what I was thinking as well. No idea why it would be different. I want to change mine to the '08 and up style though so that I have the new style plug. This would need a new harness because the 4-way wires are no longer needed.... they are essentially internal to the plug (like this one). I haven't looking at one extremely close though, so I could be mistaken as to how they hook up. Either way, I'd like to undo the wire tapping that the previous owner did on my harness by installing a new one.

Pollak 7- and 4-Pole Trailer Connector Socket w/ Mounting Bracket - Vehicle End Hopkins Wiring HM40975

I'm think'n: New Model & Style.. Wiring color code and pin position is the same.

I'd just unwrap everything the PO did, dis-connect it All.. re-connect everything according to the diagram on the 08 flip-lid.. with an 08 pigtail thats long enough to reach your OEM splice point... temporarily twist each wire together.... check it with a test light... then go from there ?

Joe