How to Use the 7 Way Plug to Power a Fuel Pump

Updated 08/05/2025 | Published 01/26/2016

Products Featured in This Question

7-Way Round RV Style Trailer Connector - Trailer Side

(381)

$13.52

Deka Jacketed 2 Wire, 10 Gauge, Brake Wire - per Foot

(323)

$2.72

Deka Heat Shrink Butt Connector - 12-10 Gauge - Nylon Insulation - Yellow - Qty 5

(1110)

$7.45

Hopkins 2-Pole Flat Wiring Extension - 12" Long

(119)

$4.08

Question:

How much power amperage in 12 volts does a 7 blade RV plug typically deliver? I have a RAM 3500 diesel, wondering if I can run a 12 volt fuel pump off it for short periods without having to connect directly to the battery.

asked by: Neal D

Expert Reply:

Good news! I can help you wire your 12 volt fuel pump to work with your 7 way vehicle plug.

To accomplish this task you will need a few things:
7-way plug # A7WCB
10 gauge wire # 10-2-1
2 pole flat wiring # HM47965
butt connectors # DW05745-5

First thing you will want to do is wire the 7 way plug with the 10 gauge wire to the ground and 12 volt power wire. The 12 volt power will be in the 1 o'clock position and the ground is in the 7 o'clock position. I've included a picture for you to see where those locations are on your connector for your convenience.

Next you will want to cut that 2 pole wire in half and connect the jacketed red wire to the 12 volt wire from 7 pole trailer connector and the white wire to the ground wire. Then for the other half of that 2 pole with the jacketed white wire to the fuel pump. These two connectors will fit together and make the connection for power to the fuel pump. It is important to have the positive circuit on the 7 pole connector wired to the protected red wire to prevent a short in the wiring in case the exposed terminal were to make contact with a ground source on the truck.

A typical 7 pole RV plug can handle up to 40 amps, if your pump draws more than that, your best bet is to hardwire it directly to the vehicle's battery.

expert reply by: Jackie C

click to enlarge

Marty

9/5/2020

My transfer pump has red and black wires. Which one should I run to the auxiliary and which to the ground on my 7 blade trailer plug?

Jon G.

9/8/2020

Usually when you see a red and black wire together the red is for power while the black is for ground. You're going to want to confirm this on your end though as wire colors aren't always a universal thing.

Marty

9/8/2020

@JonG Thanks!