2021 Kenworth T680 Fuse Box Diagram & Amperage

Quick Answer

The 2021 Kenworth T680 typically has three primary fuse box locations: one under the hood, one in the dash (often behind a kick panel or glove box), and another in the cab usually located on the passenger side firewall or in a dedicated electrical panel. Always consult your owner's manual and the fuse box lid for the most accurate and trim-specific information.

Under-Hood Fuse Box (PACCAR Engine Bay)

This fuse box is usually located on the firewall on the driver's or passenger's side, or near the battery box. It houses fuses and relays for critical engine and chassis functions.

Note: Relay locations are typically marked on the fuse box lid or housing. Always verify with your vehicle's specific diagram.

Dash / Cab Fuse Box

This fuse box is most commonly found behind a panel on the passenger side dash or kick panel. It manages electrical components within the cab.

Note: The exact number, amperage, and function of fuses can vary by trim level and installed options. Always refer to your vehicle-specific fuse diagram.

Auxiliary Cab Fuse Box (e.g., Passenger Firewell/Side Panel)

Some T680 models may have an additional fuse box located in the interior, often on the passenger side firewall, a side panel, or within a dedicated electrical compartment. This box typically handles auxiliary circuits, body builder connections, and additional cab accessories.

Trim variations are common. Always consult your vehicle's owner's manual and the fuse box lid for exact details.

How to Test a Fuse

Testing a fuse is a straightforward process:

1. Safety First: Ensure the ignition is off before working with fuses.
2. Locate the Fuse: Identify the suspect fuse using the diagrams above and your vehicle's fuse box legend.
3. Inspect Visually: Many fuses are transparent, allowing you to see if the metal wire inside is broken. If it's broken, the fuse is blown.
4. Use a Test Light or Multimeter:
   • Test Light: Touch one end of the test light to a ground point and the other to the two small metal test points on the top of the fuse. If both sides light up, the fuse is good. If only one side lights up, or neither, the fuse is blown.
   • Multimeter: Set your multimeter to continuity mode (Ω). Remove the fuse from its slot and touch the probes to each end of the fuse. A good fuse will show very low resistance or continuity. A blown fuse will show an open circuit (no continuity).
5. Replace with Correct Amperage: If a fuse is blown, replace it with a new fuse of the exact same amperage and type. Using a fuse with a higher amperage can cause severe electrical damage or fire.

Common Blown Fuses on This Vehicle

On a 2021 Kenworth T680, some fuses might be more prone to blowing due to their circuit demands or common issues. Here are a few and what to check first:

• Cigar Lighter / 12V Outlets (Dash/Sleeper): These often blow due to overcurrent from charging multiple devices or using high-power accessories. Check connected devices and ensure they are within the outlet's amperage limit.
• Trailer Brake / ABS Fuses: Heavy-duty trucks frequently experience issues with trailer wiring. A short in the trailer's electrical system can blow these fuses. Disconnect the trailer and check the truck's circuits independently.
• Blower Motor Fuses: A failing blower motor, a clogged cabin air filter, or issues with the blower motor resistor can cause the blower motor fuse (often a higher amperage fuse) to blow. Check for obstructions and listen for unusual noises from the blower.
• Headlight Fuses: While less common on modern trucks, a short in the headlight wiring or a failing bulb could potentially blow a fuse. Inspect bulb connections and wiring.
• Radio / Infotainment Fuses: Aftermarket additions or issues within the radio unit itself can sometimes lead to a blown fuse. If recently installed, recheck wiring connections.

Always remember to check related wiring for any signs of chafing, pinching, or corrosion that could lead to a short circuit.

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