DID YOU KNOW?

WILL YOUR TRUCK'S AUX SWITCH POWER A FUEL
TRANSFER PUMP?

NOT ALL AUX SWITCHES ARE CREATED EQUAL

High-current accessories should only be connected to circuits designed to handle the load.

Before connecting a fuel transfer pump, it is important to understand how the AUX circuit is designed.

"Did You Know?"
WILL YOUR TRUCK'S AUX SWITCH POWER A FUEL TRANSFER PUMP? 

Many modern pickup trucks are available with factory-installed AUX (auxiliary) switches that make it easy to add aftermarket accessories. Depending on the truck, these switches may be connected to factory-installed relays or electronic power modules designed to control accessory loads.

Before connecting a fuel transfer pump, it is important to understand how the AUX circuit is designed and how much current it is intended to handle.

DID YOU KNOW THAT NOT ALL AUX SWITCHES ARE CREATED EQUAL

A switch's primary job is to turn a circuit on and off. A relay does the heavy lifting by carrying the electrical load to the accessory.

When an AUX switch controls a relay:

  • The switch carries only a small control current.
  • The relay carries the high operating current.
  • The accessory receives power through wiring designed for the load.

This is the preferred method for operating higher-current devices such as fuel transfer pumps.

FUEL TRANSFER PUMPS REQUIRE SIGNIFICANT CURRENT

Many people focus on a pump's running amperage, but electric motors require additional current when starting.

This brief surge, known as starting current or inrush current, occurs as the motor accelerates from a standstill to operating speed. During this time, current demand can be significantly higher than normal operating current.

For example, the GPRO V25 12-volt fuel transfer pump is rated at 35 amps while running. The pump may require even more current for a brief moment during startup.

Why WIRING CAPACITY MATTERS

High-current accessories should only be connected to circuits designed to handle the load. If a pump is connected through wiring, switches, connectors, or circuits that are not rated for the required current, the result can be:

  • Excessive voltage drop
  • Reduced pump performance
  • Slow motor startup
  • Nuisance fuse failures
  • Overheated wiring and connectors
  • Premature component failure

Even if the pump operates, insufficient wire size can prevent the motor from receiving the voltage needed to deliver its rated flow performance.

Verify the Circuit Rating

Factory AUX circuits vary by manufacturer, model, and trim level. Some circuits are intended for lower-current accessories such as radios, camera systems, or work lights, while others are designed for higher-current loads. Always verify that the AUX circuit's current rating meets or exceeds the pump's electrical requirements before installation.

When in doubt, choose a relay-controlled circuit specifically designed for the accessory load.

✔ Use an AUX switch that controls a properly rated relay.
✔ Verify the circuit is rated for both the pump's running current and startup current.
✔ Ensure wiring, connectors, and circuit protection are sized appropriately for the load.
✔ Keep the truck running during fuel transfer whenever practical.

By understanding the difference between a switch and a relay, and by ensuring the electrical system is properly sized for the application, you can help your fuel transfer pump operate safely, reliably, and at peak performance.