Wiring brakes

[Airstray]

I noticed the blue brake wire as well as the large white wire go all the way to the rear of the trailer. What is the reason for this and can someone show me a wiring diagram of the blue and white wires. I assume it has something to do with the brake lights. Electricity baffles me. Thanks, Airstray

[idroba]

I believe the blue and white wires are not brake wire on your vintage units but are the charge line (+12 volts...blue) and the ground or negative wire (white). A lot of the older units had the battery in the rear compartment, and the charge lines had to run the length of the trailer. It also is used as the power for the break away switch for the brakes as well as the power wire for the electric jack.

I think, on your vintage units, yellow was the color used for the brake wires.

[Airstray]

The blue wire is definitely the brakes

[RM66caravel]

If you are replacing the vehicle trailer wire then you are updating the connector and new wiring colors apply.
Cliff

[TG Twinkie]

You did not mention what year the coach is.
The color code on vintage units is not the same as the modern trailers.

[Belegedhel]

Airstray,

I just went through this exercise with my '73. I recognize the diagram you posted above from eTrailer.com. This is the modern wire mapping, and it is NOT the same as a 70's vintage trailer is wired. Attached is the diagram from the '73 maintenance manual--might be the same for your '77, if that is what you are working on.

[RM66caravel]

Perhaps my lack of communication skills has struck again! I have removed the old wiring from my 66 added a new trailer harness and all new wiring so the pin colors on my 66 match the new 7 pin connector. It was a 6 pin cut by a po and replaced with a 4 pin. Sorry I left that part out in my reply.
Cliff

[HiJoeSilver]

If you're working on the '77 trailer, the blue wire is the charging line that goes from the tow vehicle 12v system to the trailer battery/12v system, the white is the ground from the tv to the trailer. The brake wiring in the 77 is yellow in color. New wiring harnesses have different colors. Just going through all this on my 79, and is the same in my 74 as far as colors go. If your battery/12v pannel is in the back on your model then that's why the wires go all the way back there.

[Airstray]

Sorry Guys I didn't give the year. I'm tracing the wiring on my 66 Overlander. Since all the wires are in the belly pan I have to resort to continuity. I have 6 wires at the rear. Blue-brakes, white-ground, red-lt. turn, green-rt turn, brown-running lights and black-12V. There is no yellow at the rear, don't know why so I'm using the red-back-up lights wire, called purple in the diagram, in place of yellow. I get continuity on all wires except the brakes. I pulled a drum to get to the brake wiring, needed packing anyhow, and the only way I get continuity at the drum is to connect the blue and white wires at the rear. So why does the brake wire travel to the rear? Airstray

[TG Twinkie]

The green wire is marker/clearance lights.
There is no need to have the brake wires go to the rear of the coach.
The yellow wires should exit the belly pan near the axles.
That was the old system.
If you don't have yellow, then the blue wire is the brakes and black is the charge line. These 2 wires and the white should be larger than the rest of the wires.