Adapting A Trailer With A 7-Way To A Vehicle With A 4-Flat
Updated 12/19/2025 | Published 12/18/2025
Question:
is there an adapter that will go from a 4 way flat to a 7 way on the trailer. there is no brake controller on the truck
asked by: bobby m
Expert Reply:
Hi Bobby!
While we do have a couple options for you, there is not a way to just adapt a 7-way on a trailer to a 4-flat on a vehicle that I am aware of. There will need to be some slight alterations to accomplish what you are needing to do, but it's nothing major.
The first option is to use something like the Hopkins Adapter 4-Pole to 7-Pole and 4-Pole # 37185. Your 4-flat will plug into this and you will either leave the unused wires as they are (tied up and out of the way) or cap them off. This gives you that needed 7-way, but with the unused wires not being connected, it will only have the functions of a 4-flat through it. You can run wires to these for more functions if needed, of course. It also has a 4-flat on the side, so no other adapters will ne needed. The only downside to this is you will need to find somewhere to mount it.
The other option would be to remove the 7-way on the trailer and use something like the etrailer Trailer Wiring Junction Box - 7 Terminal # e99009 and the Hopkins Endurance Easy-Pull Harness w/ 4-Pole Flat Connector - 48" # HM38134. The junction box was would make it easy to go back to a 7-way if you ever upgrade your vehicle to a 7-way. This is probably the way I would go if I were needing to do this.
Out of curiosity, what kind of trailer is it?
Michelle
12/19/2025
I purchased the Hopkins Multi-Tow Trailer Connector Adapter and it works great for connecting a 4 way flat to a 7 way. I have a Ram 3500 that has a 7 way in the bed of the truck as well as the one on the back/bumper. I use this connector to power my lights on my sled deck and it works great. I liked that I didn’t have to add any wires, drill holes in my truck to install a new plug and you can also use it to power items that have the 12v plug.