Replacing 7 Wire Trailer Harness

jbeletti

Well-known member
This morning, I replaced Tom Weber's 7 wire trailer harness.

He ran out first thing this morning to a local RV dealer and picked up the new harness. Took me about 20 minutes in total. Not sure how consistent the process is at the factory by model and over time, but most of the connections in the 4x4 electrical box at the hitch were crimped with cap-style insulated connectors. This means that you'll need new connectors.

Two of the larger wires on the trailer used twist-style red wire nuts that I was able to reuse. I ended up having 4 of the cap-style insulated crimp connectors in my stash and a few larger gauge crimp-style butt splices.

Planning to add some standard wire nuts (yellow, red and gray) to the trailer kit - just in case.

By the way, not sure how prevalent this is, but Tom thinks his connector pulled out of the receptacle during a very tight turn. Then the connector rode on the ground the rest of his trip. Ended up ground down pretty flat :eek:

I suggested he consider putting a receptacle in the bed for use when towing the 'Horn.

Jim
 

jimtoo

Moderator
In bed receptacle is the only way to go with a 5er. The ones down by the bumper leave to much weight to be supported by the plug and most are plastic. With the wind turbulence and road jar it is just more than what the plug can withstand. If the bumper plug is to be used for a 5er, I would suggest that a small bungee cord or something be used to tie the cable to the bumper near the receptacle to insure that it does not become unplugged and remove some of the weight from the plugin.
 

nhunter

Well-known member
I agree the bed mount plug is the only way to go. I soldered mine so I still have both plugs. I dislke the residencial style box under our hitch on the trailer- isn't water tight and looks out of place. When I get a chance I will upgrade to one of these. Have used them for years on industrial trailers and gravel / water doesn't seem to affect them. They have room for multiple wire entrances and clamps. Also makes it easy to trouble shoot where the problem is(power in/power out) and makes cable replacement easy.

http://grote.com//cgi-bin/goc/goc.cgi?product_number=82-1000
 

JJAK17

Active Member
I currently use the bumber mount but I am thinking of doing a bed mount. Has anyone installed their own and if so can you give me some advice.

Nhunter
I also agree that the box looks like it is too "box like" and I was looking at doing some thing different. I will have to take a look at the grote box. Thanks for the tip.


Thanks for the help.

Jason
 

jbeletti

Well-known member
nhunter,

I like that box. Looks like a simple and useful retrofit. I'd suggest using insulated ring terminals on those threaded stud contacts. That box would make easy work of replacing harnesses etc.

Jim
 

ct0218

Well-known member
Jason
You may have the wiring for the bed tied to the frame between the cab and bed. GM trucks with the factory towing package have that installed to that point. you just need to drill into the bed, pull the wire, and mount and wire the female receptacle.
 

katkens

Founding Illinios Chapter Leader-retired
Jason
Like what was mention the wire on mine was on the top of the frame, just behind the cab. Once I got it loose, I just wire tied it along the frame to rear. I mounted mine in a small ,flat indention next to the tailgate, I believe the flat area was about 6" sq. give or take. You will need a hole saw 2" or 2 1/8 " not sure with out going out to the shop and check . Drill 4 holes to mount , connect wires set to go. I almost for got there will be one extra wire in the bundle you will not use its for an extra brake light, like the one on the top of cab. Ken
 

jbeletti

Well-known member
Ken,

On Tom's harness, the yellow wire was the unused one. I just looked up the wiring diagram in the etrailer.com website and it shows the orange wire as unused and the yellow wire as the left turn signal. It all worked :D

wiring_7pole.jpg



Well..... on edit, below is a table from marksrv.com showing the yellow as unused. This is what I encountered on the Bighorn. I am not expert in this area so I can't explain the discrepancy between these 2 diagrams.

Wiring Code 7 way Trailer End
------------------------------------------
#......Color....Gage...Circuit Function
1.......white.....10...common ground
2.......blue......12...electric brake
3.......green....14...tail/running lights
4.......black.....10...battery charge (+)
5.......red.......14...left turn/stop
6.......brown...14...right turn/stop
7.......yellow...14...auxiliary/back up
NOTE: #7 is the center terminal and currently is most commonly used for backup lights.
 
Last edited:

katkens

Founding Illinios Chapter Leader-retired
Jim
This is the same diagram I used,if you grab both pictures they will plug together.;) The one on the left will be for the TV and right for the trailer plug. Nice post, Jim ,will help people make it less complicated.

Ken
 

nhunter

Well-known member
The nice peole at Ford were kind enough to stamp a diagram right on the plugin cover. Jim - the ring wire connectors work like a charm inside the box.
 

BluegrassMan

Well-known member
Hi Jim and Guy's:
As far as the orange AUX wire, I had back up lights (in my tailights) on my Sea Breeze. I think that the AUX wire was wired to those lights. It's been a long time ago, but I think that's how it was. I also had a "cyclops" third brake light on the "Breeze" as well.
 
Top