2015 Peterbilt 579 Fuse Box Diagram & Amperage

Quick Answer

The 2015 Peterbilt 579 typically features fuse boxes in several key locations to manage the complex electrical systems of a heavy-duty truck. You'll generally find them:

• Under the Hood: Usually located on the driver's side, near the firewall or battery box. This box typically houses fuses and relays for major engine components, lighting, and ABS.
• Inside the Cab (Dash Kick-Panel/Driver's Side): Often situated behind a panel on the driver's side kick panel or lower dash. This box usually controls interior accessories, HVAC, radio, and dashboard functions.
• Trunk/Cargo Area (Sleeper Compartment): For models equipped with a sleeper, an additional fuse panel may be located within the sleeper compartment to manage its specific electrical needs, such as auxiliary power outlets, lighting, and HVAC controls within the sleeper.

Under-Hood Fuse Box

The under-hood fuse box on your 2015 Peterbilt 579 is the primary distribution point for many high-current circuits, particularly those related to the engine, charging system, and major lighting components. Always consult the diagram on the inside of the fuse box cover for the most accurate information for your specific trim level.

Common Under-Hood Fuse and Relay Locations

Cab Fuse Box (Dash Kick-Panel/Driver's Side)

The fuse box located inside the cab, typically behind a panel on the driver's side kick panel or lower dash, is responsible for protecting various interior electrical components. This includes your infotainment system, interior lighting, power windows, and auxiliary power outlets. As with all fuse boxes, verify the exact layout with the diagram on the cover.

Common Cab Fuse and Relay Locations

Sleeper Compartment Fuse Box (Trunk/Cargo Area)

For Peterbilt 579 models equipped with a sleeper compartment, an additional fuse box is typically located within the sleeping area. This panel is dedicated to the electrical needs of the sleeper, including heating, air conditioning, auxiliary power outlets, interior lighting, and sometimes entertainment systems specific to the sleeper. Location can vary slightly, but it's often found behind a panel on the back wall, under the bed, or in an upper cabinet.

Common Sleeper Compartment Fuse Locations

How to Test a Fuse

Testing a fuse is a straightforward process that can help you quickly identify an electrical issue. Here's how:

1. Safety First: Ensure the ignition is off and disconnect the battery if you're working on high-amp circuits.
2. Locate the Suspect Fuse: Refer to your vehicle's fuse diagram (usually on the fuse box cover or in the owner's manual) to find the fuse for the non-functioning component.
3. Visual Inspection: Most fuses are transparent, allowing for a quick visual check. A blown fuse will have a broken wire or a dark, burnt appearance inside.
4. Use a Fuse Tester or Multimeter:
   • Fuse Tester: These inexpensive tools light up to indicate if a fuse is good. Simply touch the tester probes to the two small metal test points on top of the fuse (without removing it from the socket).
   • Multimeter: Set your multimeter to the continuity setting (often indicated by a beep icon) or the ohms setting. With the fuse removed from its socket, touch one probe to each metal blade of the fuse. A good fuse will show very low resistance or the multimeter will beep (on continuity setting). A blown fuse will show an open circuit (OL or infinity).
5. Replace (if necessary): If the fuse is blown, replace it with a new fuse of the exact same amperage rating and color. Never use a fuse with a higher rating, as this can lead to severe electrical damage or fire.

Common Blown Fuses on This Vehicle

While any fuse can blow, heavy-duty trucks like the Peterbilt 579 often experience certain failures due to their demanding usage. When troubleshooting, consider these common culprits:

• Cigar Lighter / 12V Outlets: These fuses often blow due to overloads from charging multiple devices or using high-power accessories. Check first: The devices you're plugging in. Unplug all devices before replacing the fuse.
• Blower Motor (Cab & Sleeper): Constant use of the HVAC system can eventually lead to the blower motor fuse blowing, especially if the motor is struggling or has an obstruction. Check first: For any unusual noises from the blower, or if the fan speed seems weak before it stops working entirely.
• Trailer Brake Control / Trailer Lights: Connecting and disconnecting trailers can sometimes cause spikes or shorts, leading to blown fuses for trailer-related circuits. Check first: The trailer's wiring harness for any damage or corrosion.
• Headlights / Tail Lights: While less common with modern LED lighting, older bulb-style lights or a short in the wiring can cause these fuses to blow. Check first: For any visible damage to the lamp assemblies or wiring.
• Radio / Infotainment: Malfunctions within the radio unit or connected accessories (like aftermarket chargers) can pop this fuse. Check first: Any recently installed accessories or if the radio unit itself is showing signs of failure.

Always ensure you address the underlying cause of a blown fuse, not just replace the fuse itself, to prevent recurrent issues.

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