Circuits and Functions Supported by 4-Pole Flat Trailer Wiring

Updated 07/11/2018 | Published 07/09/2018

Products Featured in This Question

Wesbar 4-Way Flat Trailer Wiring Harness - 20' Long

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Hopkins 7-Way RV Style Connector with Molded Cable - Trailer End - 8' Long - RV Standard

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$46.90

Pollak Replacement 7-Pole, RV-Style Trailer Connector Socket - Vehicle End

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Question:

4 wire trailer hook up. So what is brown, power?

asked by: Christopher

Expert Reply:

In 4-pole flat type trailer wiring such as part # 002220 the tail light circuit (also known as the running light circuit) is usually assigned to the brown wire which connects to the pin next to the ground pin. You can see this in the photo I linked for you.

This type of wiring format does not support an additional circuit for +12V auxiliary power as might be needed to top off a trailer-mounted battery or to operate a jack or winch on the trailer. Other wiring formats with additional circuits can support more functions. The 7-way wiring format, which uses connectors like # H20046 and # PK11893, has three more circuits and can support three more functions.

The linked article on wiring details the circuits available in each type of wiring format.

expert reply by: Adam R