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How To Tow Trailer W/ 7-way Blade Connector With 2013 Freightliner 122SD W/ 7-pin Round Connector


Read you qanda on this, great write up. I’m trying to wire my trailer to accept my semi truck 7-pin round male connector. In the qanda it showed 2 sockets to mount to the trailer PK11720 and PK12-707E along with a tail light converter 119178. The diagram shown was different from the taillight converter. it had a 4-pin. I’m trying to plug in my semi 7pin round into my trailer that only has the 7pin flat blade. The trailer is a 2020 EZ4 with 3 axles 6 brakes any clarity would be REALLY appreciated.


Helpful Expert Reply:

I would be happy to help you make a wiring adapter to allow you to connect your 2013 Freightliner 122SD with a 7 pin round connector to your 2020 EZ4 triple axle trailer.

First you will need a female 7-pin round # PK11720 and female 7-way blade # PK12-707E. Since the 7-pin round has separate brake and turn signals but a 7-way blade has combined you will need the the 3-wire to 2-wire converter # HM48847 like you mentioned.

This will get connected to 7-way connector as follows:

Red wire of converter to 6 o'clock pin on 7-way round
Yellow wire of converter to 5 o'clock pin on 7-way round
Green wire of converter to 7 o'clock pin on 7-way round
White wire to 12 o'clock pin on 7-way round
Brown wire to 11 o'clock pin on 7-wayround

On the other side of the converter you will make the following connections:

Green wire to the 11 o'clock pin on the 7-way blade
Yellow wire to the 9 o'clock pin on the 7-way blade
Brown wire to 3 o'clock pin on 7-way blade
White wire to 7 o'clock pin on 7-way blade

In addition you are going to need run some # 10-1-1 to make one connections which is the from the center pin of 7-way round to 1 o'clock pin on 7-way blade.

Now to install the Hayes Air Actuated Trailer Brake Controller - 1 to 4 Axles - Proportional # HA100400C you will need to connect it to the air lines on your truck using air line # RM450700 which is sold by the foot.

You will need to extend the # 10-1-1 from the blue brake output wire on the controller to the 5 o'clock pin on the 7-way blade.

Lastly you will connect the black wire from the controller to the positive terminal of the battery with a 30 amp circuit breaker # PK54530, and ground the white wire from the controller.

I included diagrams for both of these connectors, and videos of the products mentioned for you to take a look at.

7-Way Blade and Round Wiring Diagram
7-Way Blade and Round Wiring Diagram
(click to enlarge)
helpful expert reply by:
Samuel C

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