How to Make Adapter to Connect RV 7-Way to Semi Truck 7-Way

Updated 03/17/2020 | Published 03/15/2020

Products Featured in This Question

Hopkins Trailer Connector Adapter - 7-Pole Round Pin to 7-Pole RV

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10 Gauge Wire - Blue Primary - Per Foot

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Deka Jacketed 2 Wire, 10 Gauge, Brake Wire - per Foot

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16 Gauge Primary Wire - Black - Per Foot

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Pollak HD, 7-Pole Round Pin Connector w/Cable Guard

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Pollak Black Plastic, 7-Pole, RV Blade-Style Trailer Socket - Vehicle End

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Roadmaster Brite-Lite 3-to-2 Tail Light Converter for Towed Vehicles

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Question:

I have a semi with a 7 pin receptacle need to adapt to the 7 blade for my gooseneck.. that has only electric braking ...will this work? Also need to hook up a brake controller on semi...How do I go about that?

asked by: Kennth D

Expert Reply:

If you need to keep the 7-Way semi active on the truck then you would need to make an adapter to get it to work with an RV 7-Way. For that you would need a trailer side 7-Way round, # PK11702, a converter, # RM-732, and a vehicle side 7-Way RV style, # PK12-707E.

A semi-7-Way has separate circuits for the brake lights and each turn signal. And RV style 7-Way has the brake lights combined on the same circuit. So what you would do is use a circuit tester such as # PTW2993 to determine the functions of the 7-Way on the tow vehicle. Then you would place the red wire from the converter to the appropriate spot on the back of the trailer side 7-Way round for brake lights. Do the same with the green wire for right turn signal and the yellow wire for left turn signal.

You will also need additional wire to attach to the back of the 7-Way round for the other functions needed. For ground and 12 volt power you can use # 10-2-1. For running lights you can use # 16-1-1, and for electric trailer brakes use # 10-1-1.

On the output side of the converter you will attach the wires to the back of the vehicle side RV 7-Way. The green wire will attach at the 9 o'clock position, yellow goes to the 3 o'clock position. Ground goes to the 5 o'clock position, 12 volt power goes to 11 o'clock position. Running lights goes to the 1 o'clock position. The center pin is for reverse lights which is uncommon on many trailers. But if needed you will attach some wire to the appropriate pin on the 7-Way round pin and attach it to the center pin on the back of the RV style 7-Way.

The alternative is to replace the 7-Way round pin on the vehicle with a 7-Way RV style connector. You could still use # PK12-707E and converter # RM-732. What you would do is remove the 7-Way round and then use the circuit tester to determine the functions of the wires. After that you would hook up the converter wires and other wires as explained above and mount the new 7-Way to complete the installation.