What Function is Carried on Center Pin of 6-Way Round Trailer Connectors

Updated 07/21/2025 | Published 01/29/2016

Question:

On the middle inlet that says battery . where did we run that from battery or some other source

asked by: Ricky

Expert Reply:

A 6-way round-pin trailer plug like Pollak # PK11604 has a center pin that can be wired in two ways.
The most common function to be found on that center pin is 12V trailer power. This is a low-level maintenance charge that will maintain a charged trailer battery while you're driving. In other applications this center pin will carry the trailer brake signal from the brake controller mounted in the tow vehicle.

Please refer to the linked photo that shows both inside and outside views of a 6-way in both types of wiring configuration.

If your trailer is wired to have the center pin be 12V power then on the trailer this should be run to your breakaway/trailer battery. If it is wired to carry the brake controller's output signal then it should be routed to either of the two wires on each of the electric brake assemblies.

If you need to confirm which function is on your trailer plug's center pin just use a 12V battery (one in a vehicle or a spare if you have one) to apply power to the trailer's pins. You'll then see which function activates. If your center pin carries the brake circuit then you'll hear and feel the brakes engage when power is applied.

expert reply by: Adam R

click to enlarge

Al A.

7/21/2025

I just received my 6 pin socket. My problem is I can't see the #on the socket too small Can you please send me a larger Image Of the pins to complete my install.

Jon G.

7/21/2025

@AlA I don't know what each of the numbers are, but for the Pollak 6-Pole, Round Pin, Trailer Wiring Socket # PK11609 you might have better luck with the photo on this answer page - https://www.etrailer.com/question-52611.html Since these have a star-shape for the outside 5 pins you can look at the visual clues as well instead of just the numbers.