2018 Ram 3500 Fuse Box Diagram & Amperage

Quick Answer

The 2018 Ram 3500 has multiple fuse box locations to manage its extensive electrical system. You'll find fuse boxes located under the hood, inside the cabin on the passenger side kick panel, and in the rear cargo area (under the rear seat).

Under-Hood Fuse Box (Power Distribution Center - PDC)

The Power Distribution Center (PDC) is located in the engine bay, typically on the driver's side, near the battery. This box contains high-current fuses and relays for critical vehicle systems such as the engine, ABS, and major accessories. Always refer to the fuse diagram on the underside of the PDC lid for the most accurate information for your specific trim level.

**Relay Locations (within PDC): **

• R1: Engine Control Module (ECM) Relay
• R2: Fuel Pump Relay
• R3: Starter Relay
• R4: HVAC Blower Motor Relay
• R5: A/C Clutch Relay
• R6: High Beam Headlight Relay
• R7: Low Beam Headlight Relay

Passenger Side Kick Panel Fuse Box (Interior Fuse Box)

This fuse box is located on the passenger side of the cabin, typically behind a removable panel on the kick panel. It houses fuses for various interior electrical components and accessories.

Rear Cargo Area Fuse Box (Under Rear Seat)

For 2018 Ram 3500 models, especially those with additional features or a mega cab configuration, there might be a third fuse box located under the rear seats. This fuse box typically handles power for rear accessories, power outlets, and sometimes trailer connections.

How to Test a Fuse

Testing a fuse is a straightforward process. Here's how you can do it:

1. Safety First: Ensure the vehicle is off and the ignition key is removed before handling fuses.
2. Locate the Fuse Box: Identify the correct fuse box for the circuit you're troubleshooting.
3. Identify the Suspect Fuse: Refer to the fuse diagram (usually on the lid or in your owner's manual) to find the fuse associated with the malfunctioning component.
4. Visually Inspect: Many modern fuses have a visible wire inside. If this wire is broken or melted, the fuse is blown. However, sometimes a blown fuse isn't visually obvious.
5. Use a Fuse Tester or Multimeter:
   • Fuse Tester: These are inexpensive tools with a light that illuminates if the fuse is good. Simply touch the probes to the small metal test points on the top of the fuse.
   • Multimeter: Set your multimeter to the continuity or ohms setting. Remove the fuse from its slot. Touch the multimeter probes to each metal blade of the fuse. If you get a reading (continuity or close to 0 ohms), the fuse is good. If you get no reading (open circuit or infinite ohms), the fuse is blown.
6. Replace (if necessary): If the 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 a fire.

Common Blown Fuses on This Vehicle

While any fuse can blow, some are more common culprits due to high usage or external factors. For the 2018 Ram 3500, pay particular attention to these circuits if you experience an issue:

• Cigar Lighter / 12V Power Outlets: These fuses often blow due to over-drawing power with high-current accessories (e.g., air compressors, portable vacuums) or from a short circuit in a plugged-in device. If your phone charger or other accessories aren't working, check the relevant 12V outlet fuse first.
• Trailer Brake Controller / Trailer Tow Power: When towing, issues with trailer wiring or a short in the trailer itself can frequently cause these fuses to blow. If you're having trailer light or braking problems, this is a prime suspect.
• Radio/Infotainment System: Although less common, a fuse can blow if there's an internal issue with the radio or if aftermarket accessories are incorrectly wired. If your radio suddenly goes dead, check both the main power and accessory power fuses.
• Blower Motor: A failing blower motor or an obstruction in the HVAC system can cause the blower motor fuse to blow due to excessive current draw. If your fan isn't working, check this fuse.

When troubleshooting, always start with the most obvious and easily accessible fuses. If a fuse repeatedly blows, there's a larger underlying electrical issue that needs professional diagnosis.

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