Powering Signal Lights on Trailer Towed By Semi Truck with 7-Way Round Connetor

Question:

2016 peterbilt semi trying to make a gooseneck trailer plug I got all the lights to work with the adapter I bought from you plugs in truck socket and trailer plugs in the adapter only thing I cant figure out is brake lights cause you cant split of brake wire to left and right cause when you turn on left turn right turn comes on

asked by: Whitney R

Expert Reply:

The 7-Way round on your Peterbilt Semi features separate circuits for its brake and turn signal lights, while your gooseneck trailer will have the brake and turn signals combined. This is why the brake lights and turn signals aren't behaving when connected using the 7-Round to 7-Blade Adapter # HM47425 that you referenced.

To resolve this all you need to do is add a the Roadmaster Converter # RM-732 to your existing setup before the adapter. This will combine the separate circuits on the semi so that they are compatible with the trailer wiring. Doing this will allow the turn signals and brake lights to function properly when towing the trailer. The running lights wire on the truck won't pass through the converter.

I have attached a short video review that you can check out as well.

expert reply by: Chris R