I am wanting to replace my old 7-way plug with an updated newer plug & had a couple of questions looking at the current wiring. I believe from the research I have done on prior posts that the following is correct? Brown = Right turn signal Red = Left turn signal Green = Clearance/Tail Black = Brake lights Where is the ground wire? Is the big wire for the electric brakes?
There is no brake "LIGHT" wire. Blue is Brake hot to apply power to the brakes. The brake lights work from the turn signal wiring.
The code above is correct. Ground is the large white wire. Black is the hot charge wire from the vehicle. It charges the battery when on the road.
I'm not sure that is a 7 way connector. If it is, be very careful when rewiring the trailer side. The color codes on older trailers do not always follow the universal RV code. Each trailer wire must be tested separately BEFORE you install a new plug.
Testing is the only way to be fairly sure of what you have ahold of. The hardest part of testing is the same as the hardest part of making the lights work...establishing a good ground for the lighting fixtures.
My W-A-G, and it's just a guess, is that the red wire is a turn signal hot, so is the brown. When the brakes are applied it would energize both of the signal hots. The green should probably run the running and tail lights. The black is either the system ground, or it is a ground for just the brakes exclusively. Often the physical connection between the tow vehicle and the trailer was depended upon to provide the ground. The heavy white should be hot to the brakes. These old trailers did not adhere to the modern day color coding.
P.S. You can determine the brake wiring color...look under the trailer for the wiring running to the wheels. It will likely be the same colors all the way from the plug.
Do not mix ground and hot! This could cause damage to your trailer, so be sure which is which BEFORE you connect things to the new plug.
From what I can tell of the original plug, there appears to be a thicker double lead brake wire (inside might be black/white or red/white wires) Usually, the white wire is grounded to the frame. The white wire from the trailer cord should also be connected to the frame and battery negative, following the universal RV code.
I hope this helps. Take your time and do some sleuthing and testing.
vikx - yes, the wires inside the double lead are one black & one white. If the white is the ground, then what should the black wire be for? Sorry for the dumb electrical questions, I have always struggled with this stuff. Thanks!
The black wire is likely brake hot. It is connected to the 7 way blue wire. As said, not all trailers are wired correctly according to today's code. The 7 way cord black wire is 12 volt hot, so don't confuse the two or your brakes will be always on...
Also, check that the brakes are properly wired under the trailer. (most are) You should be able to trace which wire is the ground if it's connected to the frame. You want both brakes wired identically. This is going to be confusing, but it doesn't really matter which wire is which with electric brakes. In other words, the factory may have use black for ground rather than white. All that has to happen is one wire is ground and the other applies power to the magnet.
Take your time with this. We have a thread all about wiring 7 way plugs with excellent discussion.
As said, it doesn't really matter which wire is which. If they go straight to the plug without connecting to the frame anywhere, then you can use either for the ground. I like to wire both brakes identically. In other words, the top wire connects to one color, the lower wire to the other color.
I would use white for ground since you have a choice.