Is There a 4-Way Round on Truck to 7-Way on Trailer Adapter
Updated 01/05/2026 | Published 09/13/2024
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Question:
I have a tow truck with a 4 pin round light connector for trailers. I often need to pull a trailer with 7 pin round . Do you have a harness I can use? I know that i will lose the brake and power function. I will just need to operate lights. Thanks
asked by: Randall R
Expert Reply:
Hi Randall,
There is a way to do this, but you'd have to use a couple adapters since there isn't a straight 4-round to 7-round. So first you'll need an adapter for the 4-way, the Adapter 4 Round to 4 Flat # 47465.
Then for the 7-way I'm not sure if you were referring to a 7-round or a 7-blade (the difference being simply the pin shape, either rounded or flat in your 7-way). If you have a 7-round you'd use the Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round # KIT-7P-4.
If you have the more standard 7-blade you'd need the Adapter 4-Pole to 7-Pole and 4-Pole # 37185.
Product Page this Question was Asked From
Custer Trailer Connector Adapter - 4-Way Flat to 7-Way Round
- Custom Fit Vehicle Wiring
- Wiring Adapters
- Universal Fit
- 4 Flat to 7 Round
- Plug and Lead
- Custer
more information >
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Jerred H.
1/5/2026
Hey Randall, did the adapter setup with the 4-round to 4-flat and then to the 7-way work out for your tow truck and trailers? Knowing how it performed could help others trying to connect similar setups.