Is Adapter Needed to Tow Trailer with 5-Way Flat with a Harley Ultra Classic with 4-Way Flat

Published 06/03/2015

Products Featured in This Question

Adapter 4-Pole to 5-Pole Trailer Wiring Adapter - Shorter

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2-to-3 Tail Light Converter for Towed Vehicles w/ Incandescent Tail Lights

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Hopkins Endurance 5-Way Flat Trailer Connector - Vehicle End - Ergonomic Design

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Question:

Have a 2009 harley davidson ultra classic that has a 4 wire flat trailer plug on it. i just got a new trailer that has a 5 wire set up. do i need to buy a 5 wire to 4 wire adapter to make this work correctly. was not sure if i could jummper some wires to make it work. please let me know asap and i appricate any info you can provide.

asked by: Gregg S

Expert Reply:

Many times a 5-Way flat trailer connector will plug into a 4-Way flat connector. But if it doesn't then you would need an adapter such as # 47515. If the trailer is designed for use behind a motorcycle I am curious as to what the functions are for each of the 5 pins.

On a typical 4-Way flat connector on a vehicle there is aground pin, running light pin, left turn signal/brake light pin, and right turn signal/brake light pin. And on a vehicle with a 5-Way flat the functions are the same and the 5th function is usually tied into the reverse light circuit to operate an electric reverse lockout solenoid on a trailer with hydraulic brakes.

You don't see reverse lights on motorcycles so if you can tell me the functions of the 5 pins I can determine if something else is needed to make the 2 connectors compatible. It is likely that the trailer uses 1 wire each for left and right turn signals and brake lights so you would need a converter such as # 118158.

You would cut off the 4-Way end on the motorcycle and connect the wires to the input wires on the converter (the brown running light wire will bypass the converter). Then on the output side you will have yellow for left turn, green for right turn, and red for brake lights. You would then wire these wires plus the brown wire to a matching vehicle side 5-Way connector such as # HM47900 for a 5-Way flat.

expert reply by: Michael H