How to Adapt 7-way Round Pin Trailer Connector on Kenworth Tractor to RV Blade Style 7-Way
Question:
I have a class 8 Kenworth tractor with a standard for tractor trailer round pin 7 wire plug . The Kenworth tractor has separate wires for turn and stop lights.3 wire. I want to tow a trailer with standard rvinch 7 wire round plug that has stop lights combined w/turn signals 2 wire …… can you tell me what adapter/convertor to use please . thank you
asked by: Doug M
Expert Reply:
There isn't an off-the-shelf adapter that'll do exactly what you're wanting to do, but you can certainly piece one together. Your best bet would be to install a taillight converter and a 7-way RV blade-style trailer connector on the Kenworth tractor. This way, you'd have 2 functioning trailer connectors.
I'd recommend using the # 119250KIT taillight converter which would tap into the circuits feeding your tractor trailer 7-pin round plug. The yellow wire taps into the feed for the left turn signal, the green into the right turn, the red into the brake the brown into the running light circuit and the white wire into the ground. The black wire connects to the positive battery terminal. I'll link you to our wiring help article that includes photos showing how the 7-round pin is wired.
Then, you'd use an adapter like # 37185. The 4 pole from the converter would plug into the 4 pole on the adapter, then there'd be 4 loose wires to connect. Ground the white wire, the black wire connects to a 12-volt power source, the blue wire is used to carry the output voltage from a brake controller if the trailer has brakes and the purple wire is usually used for reverse lights. Other than the ground, if the other three wires aren't needed, you can bundle them up out of the way.
You could use the # HM47425 adapter you referred to, and tap the converter's inputs and outputs inline between the 7-way round pin and 7-way blade, but I believe the method outlined above would make for a simpler and cleaner install.
Products Referenced in This Question
ZCI Circuit Protected Vehicle Wiring Harness w/ 4-Pole Flat Trailer Connector and Installation Kit
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Converter
- Universal Fit
- 4 Flat
- Tekonsha
more information >
Adapter 4-Pole to 7-Pole and 4-Pole
- Trailer Wiring
- Wiring Adapters
- Multi-Function Adapter
- 4 Flat
- Plug and Lead
- 4 Flat
- 7 Round - Blade
- Hopkins
more information >
Product Page this Question was Asked From
Hopkins Trailer Connector Adapter - 7-Pole Round Pin to 7-Pole RV
- Trailer Wiring
- Wiring Adapters
- Single-Function Adapter
- 7 Round - Round
- Plug and Lead
- 7 Round - Blade
- Hopkins
more information >
Featured Help Information
Instructions
Miscellaneous Media
Continue Researching
- Shop: Trailer Wiring
- Shop: Roadmaster Hy-Power Diode - (Qty 1)
- Shop: Hopkins Trailer Connector Adapter - 7-Pole Round Pin to 7-Pole RV
- Article: Trailer Wiring Diagrams
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Article: Brake Controller Installation: Starting from Scratch
- Q&A: Converting From 7-Way Round to 7-Way Flat Connector
- Q&A: Availability of 7-Way Round to 7-Way Blade Adapter
- Article: Gooseneck to 5th Wheel Adapters
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Q&A: How to Make an Adapter to Go from Semi Truck 7-Way Round to RV Style 7-Way Blade on Trailer
- Q&A: Semi Trailer Light Function Locations on Heavy Duty 7-Way Pin Connection
- Q&A: Will the BOLT Trailer Hitch Receiver Lock Work on 2022 Thor Magnitude on Ford F-550 Chassis
- Q&A: Determining If 2018 Toyota Sienna XLE has Factory Tow Package and Recommended Trailer Hitch
- Article: Trailer Maintenance Schedule
- Article: Towing a Trailer? Let's Talk About Brake Controllers
- Q&A: Size Hole Needed to Install 4 inch Trailer Taillight that is Flush Mounted
on Trailer Wiring
