7 Way Tow Wiring

Just had this discussion with my Daughter last night. They were rewiring there trailer (drug the cord). Being a old truck mechanic I wanted to wire it different till she showed me the wiring diagram for the trailer. Thanks for the post

This is what shows on my 61 Shasta
Red green brown and black then a separate black n white and one additional white.

I used a 4 way flat on my jeep connecting to the trailers Green Red and Brown using the conversion of yellow to red and all works. Tail lights tear drops turn signal and brake lights. So my question is what are the other wires for?
Black and white almost looks like roamex but I believe is original. Then there is the additional white which looks like a ground.
Electric brakes?
Anyone have photos of what the original connector end is?
Not familiar with what a 7 way looks like.

Thanks 10! Test your wiring as above and you'll know which does what...

I'm guessing your extra white is a ground and the other two are brakes. Easy enough to trace them to the backing plates. Most trailer brake wiring is black and white or red and white. Of course the 7 way blue goes to brake hot.

Sometimes you can trace a wire to the frame (GROUND)as well. Easiest wire to identify if it's still connected.

Alilbs,

Testing the wires is recommended. Do NOT use your vehicle as a test power source.

Find the ground first. Start with WHITE and see if it goes to the frame or skin anywhere. If it is directly connected to something metal, that's your ground.

The BLUE "might" be electric brake hot. Get under the trailer and see if you can trace to the backing plate. You might have to remove tape to see what wire goes to what.

As far as the other wires, you have to test. Clean the light sockets and be sure the light plates are well grounded before starting.

If you had a 4 way plug on the trailer, I'm guessing:

BROWN is running lights and tails (TM)
GREEN is Right Turn
YELLOW is Left Turn

To test, ground a portable battery to the trailer frame and lightly touch each wire above to the hot side. Some of the lights should glow if your grounds are good. Label each and go to the next.

For the 7 way connection, you must *change* the color code to today's RV universal code:

GREEN is TM
BROWN is LT
RED is RT Note the switch on Green and Brown. Red is connected to the 4 way yellow.

Again, Test the wiring before connecting. The above is educated guesses. Hope this helps.

NOTE: THE ABOVE IS AN IMAGE OF THE VEHICLE SOCKET. It is correct for the 7 way code you should be using and the colors are usually stamped in the plastic on the wiring side. In other words, you can see "green" when inserting the Tail/Marker wire.

Btw, here's what's on my truck... The same as the image above.

I think I can explain the different connection in the 7 way plugs. I'm familiar with 2 systems that use the same plug. Semi and RV, the plugs swap but the wires do different things.
Being that the semi standard existed before the RV standard, its not surprising that some really old trailers may be wired to that standard.

Inspection and testing is the only way to know for sure.

Also, if you're installing a plug on your tow vehicle, don't assume the manufacturer used RV standard color for the truck wiring. Find a wiring diagram or do plenty of testing. I've had to fix plenty of botched installs over the years.

Note: many pickups and bigger SUV's since the early 2000 have wiring on them for trailer hookups even if the brake control and rear plug aren't present. Pays to look and parts stores may have what you need for a plug in install.