2020 Ford F-350 Super Duty Fuse Box Diagram & Amperage

As an ASE-certified master technician, I’ve spent plenty of time tracing electrical gremlins on Ford’s Super Duty lineup. The 2020 Ford F-350 Super Duty is an absolute workhorse, but with its advanced towing features, robust diesel and gas engine options, and sophisticated SYNC infotainment systems, its electrical system is complex. Whether you've lost power to your trailer brakes, your 12V accessory outlet stopped working, or your blower motor quit on a hot day, knowing where your fuses are and what they control is half the battle.

Disclaimer: Fuse configurations vary based on engine type (6.2L V8, 7.3L V8, or 6.7L Power Stroke Diesel), trim level (XL to Limited), and optional equipment. Always verify with the printed legend on the inside of your fuse box lid.

Quick answer

On the 2020 Ford F-350 Super Duty, there are two primary fuse box locations you need to know about:

1. Under-hood Fuse Box (Battery Junction Box): Located in the engine compartment on the passenger side, near the firewall and battery. This box contains high-current fuses and relays for major powertrain and chassis components.
2. Passenger Compartment Fuse Box (Body Control Module): Located on the passenger side, behind the kick panel down by the passenger’s right foot. This panel houses fuses for interior electronics, lighting, and cabin accessories.

(Note: There is no trunk/cargo fuse box on the F-350 pickup trucks).

Under-hood Fuse Box (Battery Junction Box)

The under-hood Battery Junction Box (BJB) handles the heavy lifting. It houses the high-amperage cartridge fuses (J-case), mini fuses, and relays that protect the engine control module (ECM/PCM), starter, ABS, and external trailer connections.

Note: Headlights on the 2020 F-350 are generally controlled electronically by the BCM. Instead of traditional dedicated fuses for low/high beams, the BCM monitors the circuits and will shut down power in the event of a short.

Passenger Compartment Fuse Box (Kick-Panel)

The passenger compartment fuse box is built into the Body Control Module (BCM) located behind the right-side kick panel in the passenger footwell. Pull the trim panel straight back toward you to release the clips and access the fuse block.

How to test a fuse

When a component fails, the first and easiest step is checking the fuse. Here is the proper way an ASE technician tests a fuse:

1. Visual Inspection: Pull the suspect fuse using a fuse puller or needle-nose pliers. Hold it up to a light source. If the internal metal wire bridging the two blades is melted, broken, or scorched, the fuse is blown and must be replaced.
2. Using a Multimeter (Continuity Test): If the visual inspection is inconclusive, set your digital multimeter to the continuity setting (the one that beeps). Touch one probe to each blade of the fuse. If you hear a beep, the fuse is good. If it's silent, the fuse has failed.
3. Using a Test Light (In-circuit Test): You can test fuses without removing them. Clip the test light's ground wire to a good bare-metal ground. Turn the ignition to the "ON" position (do not start the engine). Touch the test light probe to the two small exposed metal testing ports on the top of the fuse. If the test light illuminates on both sides, the fuse is good. If it only lights up on one side, the fuse is blown.

Important: Never replace a blown fuse with one of a higher amperage rating. Doing so can cause the wiring harness to overheat, potentially leading to an electrical fire or severe damage to modules like the PCM or BCM.

Common blown fuses on this vehicle

Based on my experience in the shop, F-350 Super Duty owners frequently run into a few specific electrical issues:

• Trailer Tow Fuses (Fuses 6, 20, & 32 - Under-hood): Super Duty trucks are built to tow, but faulty wiring on trailers is incredibly common. A shorted wire on your boat or RV trailer will quickly pop the stop/turn fuse (F20) or trailer brake module fuse (F32). What to check first: Inspect your trailer's 7-way plug for corrosion and check the trailer's wiring harness for rubbing or damage before replacing the fuse.
• 12V Power Points / Cigar Lighter (Fuse 37 - Passenger Box): Power inverters, tire inflators, and phone chargers are notoriously hard on 12V outlets. If an accessory pulls more than 20 amps, or if a penny falls into the socket, this fuse will blow immediately. What to check first: Remove any accessories plugged into the dash and check the socket for debris before inserting a new fuse.
• Data Link Connector / OBD2 (Fuse 32 - Passenger Box): If your F-350 won't communicate with an emissions inspector's computer or your personal scan tool, check this fuse. What to check first: This circuit sometimes shares power with accessory systems; ensure no aftermarket electronics are tapped into this circuit.
• Blower Motor (Fuse 31 - Under-hood): If your A/C and heat controls work but no air blows from the vents, the 40A blower fuse or Relay 12 might be the culprit. What to check first: Blower motors draw more amperage as they age and their bearings wear out. If this fuse blows repeatedly, you likely need a new blower motor, not just a new fuse.

If you are dealing with a fuse that blows repeatedly after being replaced, you have a short-to-ground in the wiring harness or a failed component drawing too much current. Don't risk further damage to your Super Duty's expensive electrical system.

Find a trusted shop on Repairius.