7-Way Round to 4-Way Flat Adapter for Semi Truck
Updated 01/27/2026 | Published 08/24/2024
Products Featured in This Question
Question:
Hey, Im looking for a plug adapter to go from my 7 pin round semi truck to a 4 pin regular car trailer. Any help would be greatly appreciated even if I have to get an adapter from 7 round to 7 blade then 7 blade to 4 pin. I do not need to control the trailer brakes just the lighting/turn signals. Thank you.
asked by: Richie F
Expert Reply:
Hi Richie; there are no adapters that are designed for this but you can make your own. A standard adapter like the # 47405 works with your standard 7-way and trailer wiring which doesn't require a converter. The lights on your semi are separate which means a converter will be required to make it compatible with the combined lights on your trailer. You can put this together using the Pollak 7-Pole Round Pin Connector # PK11700, Hopkins Tail Light Converter # HM48847, and Hopkins 4-Way Flat Trailer Connector # HM48035.
Robin H.
1/27/2026
Hey Richie, how did your wiring setup go using the Pollak connector, tail light converter, and 4-way flat connector? Your results could really help others trying to connect a semi truck to a small trailer.