2018 Ram 2500 Fuse Box Diagram & Amperage Guide

As an ASE-certified master technician, I’ve spent countless hours tracking down electrical gremlins in heavy-duty trucks. If your 2018 Ram 2500 has a suddenly dead radio, missing trailer lights, or won’t start, checking the fuses is always step one. Today, we’re diving into the fuse box diagram, amperage ratings, and circuit locations for the 2018 Ram 2500.

Quick answer: 2018 Ram 2500 Fuse Box Locations

Unlike many modern vehicles that scatter fuse boxes between the engine bay, dashboard, and cargo area, the 2018 Ram 2500 keeps things relatively simple. There is only one primary fuse box on this vehicle:

• Under-Hood Power Distribution Center (PDC): Located in the engine compartment on the driver’s side, near the battery. It has a black plastic cover secured by a couple of push-clips.

(Note: Depending on your trim—Tradesman, Laramie, Power Wagon, or Cummins diesel versus HEMI gas—there may be slight variations or auxiliary upfitter modules. Always verify the printed legend on the inside of your fuse box lid before pulling or replacing fuses.)

Engine Compartment: Power Distribution Center (PDC)

The PDC houses almost all of the critical electrical circuits for your 2018 Ram 2500, including the ECM, fuel pump, lighting, radio, and trailer braking system. It also contains several micro relays and standard relays for high-draw components like the starter and blower motor.

Below is the most common configuration for the 2018 Ram 2500. Keep in mind that depending on your specific engine and trim level, some slots may be empty or serve a slightly different function.

Common Relay Locations in the PDC:

• Run/Start Relay: Powers ignition-switched circuits.
• Starter Relay: Engages the starter motor.
• Fuel Pump Relay: Often integrated into the TIPM/PDC board, but check external micro-relays for fuel system power.
• A/C Clutch Relay: Engages the air conditioning compressor.
• Blower Motor Relay: Supplies heavy current to the cabin fan.

(Always cross-reference the exact relay diagram etched into your fuse box lid, as Mopar frequently shifts relay positions between the HEMI and Cummins configurations).

How to Test a Fuse

As a mechanic, I always tell folks not to just "eyeball" a fuse. While you can sometimes see a broken wire inside a blown fuse, a hairline fracture can easily trick you.

1. Use a Test Light or Multimeter: The easiest way to test a fuse is with a 12V test light. Turn the key to the "ON" position (engine off). Ground the test light clamp to a clean metal surface. Touch the probe to the small metal test points on top of the fuse. If the test light illuminates on both sides, the fuse is good. If it lights up on one side but not the other, the fuse is blown.
2. Pull and Inspect: If you don't have a test light, use the fuse puller tool (usually clipped inside the fuse box lid) or a pair of needle-nose pliers to gently pull the fuse. Hold it up to the light. The metal "U" or "S" shaped wire inside should be continuous. If it's broken, melted, or blackened, the fuse is blown.
3. Always Replace with the Same Rating: Never put a 30A fuse in a 10A slot. This is a surefire way to melt wiring harnesses or cause an electrical fire. Stick to the exact amp rating and color code specified.

Common Blown Fuses on the 2018 Ram 2500

Heavy-duty trucks work hard, and some circuits take more abuse than others. If you're dealing with electrical issues on your 2018 Ram 2500, check these common culprits first:

• Trailer Lighting (F53, F81, F60): Hauling trailers means dealing with suspect trailer wiring. A short in your trailer’s harness will immediately pop the right or left turn/stop fuses in your Ram's PDC to protect the truck's main body module. If you lose trailer lights, check these fuses and inspect your 7-way plug for corrosion.
• Cigar Lighter / 12V Outlets (F90, F91, F93): Phone chargers, power inverters, and tire inflators often draw too much amperage or have cheap connectors that short out the socket. If your devices aren't charging, a 20A Yellow fuse is almost certainly blown.
• Air Conditioning Clutch (F62): If your blower motor works but the air isn't blowing cold, the A/C compressor might not be engaging. Check the 10A Red F62 fuse. If it’s blown, there may be excessive resistance in the A/C clutch coil.
• Integrated Trailer Brake Controller (F11): Ram's factory trailer brake controllers are great, but heavy braking loads can sometimes pop the 30A fuse. If your dash reads "Trailer Brake Disconnected," inspect F11 before replacing the controller module.

Dealing with an electrical issue you just can't track down? Fuses blowing repeatedly indicate a dead short somewhere in the wiring harness or a failing component. Find a trusted shop on Repairius to get your heavy-duty Ram back on the road safely.