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What Are The Standard Colors And Functions For A 4 Flat On A Cargo Trailer

Question:

Ive got 5 wires black white brown green and yellow. Can I use a 4 way flat plug and what wire configuration do I use. On the replacement I bought it only has 4 wires. White brown yellow and green

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Expert Reply:

The standard 4 Flat will have the White (ground), Brown (running lights), Yellow (left turn and brake), and Green (right turn and brake). Black will typically be used for 12 volt power, but can also be any number of things. The only way to know for sure what it is used for will be to trace it to its source. However, if you only need the 4 standard functions, you can definitely just cap that off and use something like the Hopkins 4 Flat # HM38168.

With that said, if you do trace it and find that it goes to reverse lights, you can use the 5 Flat plug # 20017 to get the extra wire attached. The Tow Ready Vehicle Side 5 Flat # 20036 can then upgrade the 4 Flat on your vehicle with the wire being spliced into a wire going to your reverse lights. Then your trailer will have reverse lights when you back up with it.

If it ends up being a 12 volt power line to something, it will be much the same, but I recommend putting a 7 Way plug on instead of a 5 Flat. A 7 Way, like the hopkins # H20046, can also be used if it is a reverse light wire and if you already have a 7 Way on your vehicle, I recommend going this way. The only difference between wiring this for a 12 volt line will be which wire you connect the black one to. I have the functions listed below if you choose to go this way.

Brown - right turn/stop,
Red - left turn/stop
Green - running lights
Yellow - auxiliary/reverse light
White - ground
Black - 12 volt hot lead

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Lazer S

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