Do I Need an Adapter to Go from a 5-Pole Flat Vehicle Connector to a 4-Pole Flat Trailer Connector?

Question:

I recently had a flatbed put on my truck. It came with a rv plug and a 5 pin flat plug. I’ve never seen a 5 flat pin before but my one little trailer has 4 flat. Is there an adapter that goes from 4 to 5 flat? I do have a RV to 4 adapter but I’d prefer flat to flat. Can you help me ?

asked by: Dan F

Expert Reply:

Typically the 5-Way Flat is used for trailers with surge brakes or hydraulic brakes. The additional wire is tapped into the backup lights to disengage the hydraulic trailer coupler (actuator) when the vehicle is reversing, thus turning off the trailer's brakes.

That being said, there isn't an adapter out there to convert a vehicle's 5-pole flat into a 4-pole flat because it's not needed. All you have to do is plug the 4-pole trailer connector into the 5-pole vehicle connector. Doing this leaves the one (reverse light circuit) pin exposed on the vehicle's 5-way connector which you have no use for.

You also have the option to use an adapter like # HM47910 to covert your current trailer's 4-pole flat into a 5-flat to match your trailer. This will give you the option to add brakes to your trailer if you decide to do so in the future.

I have attached a photo for reference.

expert reply by: Carla M