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Adapting 5 Pin Round Connector on Harley-Davidson to 4-Pole Flat Trailer Connector


my new harley has a five wire round plug on the hitch but my traile has only got a four wire flat plug on it what wire do i not have or not need ???? how do I do this my trailer has four tail lights and one set of marker lights on the side but nothing fancy


Expert Reply:

The extra wire on your 5 pin H/D plug will serve one of two purposes. It is either the brake light signal or a constant 12-volt power feed to the trailer. You can easily determine which case you are dealing with by using a circuit tester like part # 40376 on the plug. Activate the turn signals, running lights and brakes to determine which pin carries which circuit. If the extra pin carries a constant 12-volts, and your trailer does not require any power supply, you could simply construct an adapter using parts # PK11501 and # 18172.

I believe you will find that your 5 pin connector has one pin that carries the left turn, one pin for the right, and one pin for the brake lamp. Your trailer with the 4-pole connector most likely carries the brake lamp and right turn signal one one circuit and the left turn and brake on the other, with the remaining pins being running lamps and ground (if the trailer does not have amber turn signal lamps, this is the case) In this case, you will need a tail light converter like part # 119190KIT to take the existing separate brake and turn signals from your bike and combine the three circuits into two circuits like a car trailer.

This unit can be installed permanently onto the bike by removing the existing 5 pin plug and wiring it directly to the inputs on the converter. The black 12-volt power wire would connect to the positive battery terminal via the included fuse holder.

expert reply by:
Mike L

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