2014 Peterbilt 579 Fuse Box Diagram & Amperage

Quick Answer

The 2014 Peterbilt 579 typically features three main fuse box locations: one under the hood, a primary fuse panel inside the cab (usually on the passenger side kick panel or behind the glove compartment), and a third in the sleeper compartment (if equipped).

Under-Hood Fuse Box

This fuse box, often located near the battery box or firewall on the driver's side, primarily houses fuses and relays for high-current circuits and critical engine functions. Always consult your vehicle's specific fuse box lid diagram for exact layouts, as configurations can vary slightly.

Common Relays in this location often include:

• Starter Relay: Engages the starter motor.
• ECM Main Relay: Supplies power to the Engine Control Module.
• Fuel Pump Relay: Powers the fuel pump.
• Headlight Relays: Controls high and low beam circuits.

In-Cab Fuse Box (Passenger Side Kick Panel / Glove Compartment)

The main in-cab fuse panel is typically located behind the passenger side kick panel or accessible by removing the glove compartment. This panel contains fuses for interior accessories, comfort features, and various electronic modules.

Common Relays in this location often include:

• Accessory Relay: Controls power to various cabin accessories.
• Blower Motor Relay: Powers the cabin blower fan.
• Ignition Relay: Powers various switches and modules when the key is on.

Sleeper Compartment Fuse Box

For 2014 Peterbilt 579 models equipped with a sleeper, a dedicated fuse box is typically found within the sleeper compartment. This panel manages power for sleeper amenities and auxiliary functions.

Common Relays in this location often include:

• Sleeper Main Power Relay: Supplies primary power to the sleeper fuse box.

How to Test a Fuse

1. Locate the Fuse Box: Refer to your owner's manual or the quick answer section above to find the correct fuse box.
2. Identify the Suspect Fuse: Look at the fuse box diagram (usually printed on the inside of the fuse box cover) to identify the fuse for the circuit that has failed.
3. Visual Inspection: Most fuses are clear plastic. A blown fuse will have a visibly broken or melted wire connecting the two terminals inside. If it's a opaque maxi-fuse, you won't be able to see the element.
4. Use a Fuse Tester or Multimeter:
   • Fuse Tester: These inexpensive tools light up if the fuse is good. Simply touch the tester probes to the two small metal test points on the top of the fuse (or remove the fuse and test across its terminals).
   • Multimeter: Set your multimeter to the continuity or ohms setting. Remove the suspect fuse from its holder. Place one probe on each metal terminal of the fuse. A good fuse will show very low or zero resistance (continuity). A blown fuse will show infinite resistance (open circuit).
5. Replace (if blown): If a fuse is blown, replace it with a new fuse of the exact same amperage rating and type. Using a fuse with a higher amperage can cause serious electrical damage or fire.

Common Blown Fuses on this Vehicle

While any fuse can blow, some common culprits on a 2014 Peterbilt 579, especially given the demands of heavy-duty use, include:

• Cigar Lighter / 12V Outlets (In-Cab and Sleeper): These frequently blow due to overloads from charging multiple devices or using high-power accessories. Always check the amperage draw of your devices.
• Blower Motor Fuses (Cabin and Under-Hood): A failing blower motor or an obstruction in the fan can cause these high-amp fuses to blow.
• Trailer Brake / Trailer ABS Fuses: Issues with the trailer's wiring or a short in the trailer's electrical system can lead to these heavy-duty fuses blowing.
• Headlight Fuses: Especially if using aftermarket bulbs or if there's a wiring issue in the headlight circuit.
• Radio / Infotainment Fuses: Can blow if there's a short in the unit itself or if aftermarket accessories are incorrectly wired.

What to Check First: Before replacing a fuse, consider what accessory or system was in use when the problem occurred. If you just plugged in a high-power inverter, for example, the cigar lighter fuse is a good place to start your investigation.

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