'97 E-350 trailer wiring - Diesel Forum

cpl0313 · 08-09-2006, 08:58 PM

My neighbor just bought a '97 E-350 motor home and it came wired with a flat four pin connector for a trailer. He needs a seven pin round plug. Is there a connector under the dash like on his '97 F-250 to plug a brake controller into? If not what does he need to do to accomplish this. Thanks for the help.

RussBarnes · 08-15-2006, 12:20 PM

I have the same question about my '03 E350. I mounted the 7 pin connector at the rear, wired in the four wires from the supplied harness connector I cut off. Ran three 10 gauge wires forward; one for 12v., one for brakes and one for reverse (I have a trailer with disc brakes that needs the back up light feature).

I have the harness at the front, the Prodigy installed and darn if this isn't the most complicated wiring I've seen. My experience has been on GM's and it was easy to find switched 12v. under hood. All I can find here is full time 12v. next to the power panel. And GM's were easy to tap into the fuse block for the switched 12v. power to the controller, but this is the tightest bundle of snakes I've seen. And I searched all over under the dash for a connector to the controller and this stripped E350 doesn't have one since it didn't have the towing option.

Has anyone out there any experience at wiring one of these from scratch? Camping World won't do it since they "don't install used equipment".

carringb · 08-16-2006, 08:02 PM

The E-serise cutaway chassis has tow wiring already. It terminates on the left frame rail above the rear axle if extended properly by the MH builder, or if not, then anywhere along the left side (and sometimes bundled up near the cab). The brake controller wiring is near the floor behind the parking brake. You may have to install a relay into the power distribution box for running and or backup lights.

RussBarnes · 08-17-2006, 01:46 PM

At least pulling all the kick panels on the van is easy. I went to the back up light bulb and found the color wire for the reverse wire, traced it in the harness by the parking brake and skinned it, wrapped and soldered. I did the same for the third brake light to trigger the Prodigy. The ground was easy and the blue wire to my new harness was a snap. I have searched and searched and on my E350 without a towing option I couldn't find any obvious trailer controller wiring. The four wire plug was tucked away nicely at the rear of the frame, but there certainly isn't any wiring that in anyway resembles the rest of what is needed to connect to a 7 way.

As to the B+ to the trailer for battery charging. I went with the full time 12v. at the power box and added an in-line fuse for protection. I don't want to install a relay, unless I get tired of pulling the 7-way when parked.

I love this truck, but it sure is harder to wire for a trailer than my previous ones were.

Thanks carringb for the response.

beaker · 08-24-2006, 07:51 PM

I've checked into the same thing on my 03 E350. From what I found, the trailer brake controller wiring connector is there by the left kick panel. You need to connect to your brake controller using the 5-wire pigtail, which is F4UB 14A348 E498G I believe. The relay under the hood is missing as well, but looks like it would just plug in.

The hard part appears to be the wiring along the frame. From what I found, the three additional wires that come with the 7-way appear to end at the big honking connector that has the 8mm bolt in it just left of the transmission. You would need a new harness that runs from there along the fuel tank to the rear axle. I believe it includes wiring to the rear axle ABS. The 7-way harness at the rear has two sets of wires that run to the rear axle area. One goes to the same connector as the existing 4 way flat does, and the other connects to the wiring harness that you don't have.

I've been too afraid to price this harness out, but it appears to be the main component needed to upgrade to a factory 7-way.