How To Differentiate a Two Wire and Three Wire System

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Differentiating a Two Wire and Three Wire System

Today we are going to do the Frequently Asked Questions of what is the difference between a three wire system and a two wire system. It is actually very easy and very simple. All it is, is you take away two wires and the same thing applies to the four and five wire system. Starting off on the car side we are going to attach the wiring to, we are going to have five wires. Green is going to be right turn, red is going to be the brake signal, yellow is going to be left turn, brown is going to be your running lights, and the white is going to be ground. When you talk about the three wire system you are only talking about the right turn, the brake signal, and the left turn. You omit the brown wire and the white wire. That is our three. On the two wire system you are only dealing with the two combined signals, the brake signal and the turn signal on the same wire. We are only dealing with the left and right turn. 00:46

Next we will show a couple of examples of a two wire system compared to a three wire system. First we are going to show you a version of a two wire system. We are going to use my little truck and we are going to show the turn signal first and then we will stop that and we will turn on the brake signal. I have got my left turn signal on and now hit the brake and you see the actual same bulb turns on. That tells you that it is a combined system. In this vehicle it is going to be very easy to see that we have a three wire system. First off we have got the yellow turn signal to tell us right away that is going to be a separate system. Yellow is going to be the turn signal and the red on the bottom is going to be our brake light. Just to reiterate we will turn on our turn signal and then we will hit the brake signal and you can see the difference so that means we have got a three wire system.

Questions and Comments about this Video

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How to wire from the van to the wireing to the the trailer harnest that go to the van

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Rachael H 06/03/2014

On the van you will need to identify the left, right, brake, and ground wires. It is best to use a circuit tester like the # 40376 to confirm the functions of each wire, and not reply on vehicle wiring colors. You will then need to splice yellow wire into the left turn signal wire, the green wire into the right turn signal, the red wired splices into the brake signal, and the white wire is connected to an appropriate metal surface to serve as a ground.

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