2021 International LT Fuse Box Diagram & Amperage
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Quick answer
The 2021 International LT has two main fuse box locations:
- Under-Hood Fuse Box: Located in the engine compartment on the driver's side, near the firewall.
- Cab Fuse Box: Located in the passenger-side footwell, behind a kick-panel.
Note: Fuse and relay configurations can vary based on the specific trim and options package of your vehicle. Always consult the diagram printed on the inside of your fuse box lid to confirm the correct layout for your truck.
Under-Hood Fuse Box (Engine Compartment)
This fuse box contains high-amperage fuses and relays that control critical engine and chassis systems.
| Fuse # | Amp | Color | Circuit / Component Protected |
|---|---|---|---|
| F1 | 60A | Yellow | Trailer Power Feed |
| F2 | 40A | Green | ABS Module Power |
| F3 | 30A | Pink | Starter Motor Solenoid |
| F4 | 30A | Pink | Engine Control Module (ECM) Power |
| F5 | 20A | Blue | Fuel Pump |
| F6 | 20A | Blue | Ignition Coils |
| F7 | 15A | Light Blue | A/C Clutch |
| F8 | 15A | Light Blue | High Beam Headlights |
| F9 | 15A | Light Blue | Low Beam Headlights (Left) |
| F10 | 15A | Light Blue | Low Beam Headlights (Right) |
| R1 | Relay | Black | Starter Relay |
| R2 | Relay | Black | Fuel Pump Relay |
| R3 | Relay | Black | A/C Clutch Relay |
| R4 | Relay | Black | ECM Relay |
Cab Fuse Box (Passenger Footwell)
This fuse box handles most of the interior and body control circuits, including lighting, accessories, and infotainment.
| Fuse # | Amp | Color | Circuit / Component Protected |
|---|---|---|---|
| F12 | 20A | Blue | Cigar Lighter / 12V Power Outlet 1 |
| F13 | 20A | Blue | 12V Power Outlet 2 |
| F15 | 30A | Pink | Blower Motor (HVAC Fan) |
| F18 | 10A | Red | Radio / Infotainment System |
| F19 | 10A | Red | Brake Lights (Stop Lamps) |
| F21 | 15A | Light Blue | Airbag (SRS) Control Module |
| F22 | 10A | Red | Instrument Cluster |
| F24 | 15A | Light Blue | Trailer Brake Control |
| F29 | 10A | Red | Tail Lights & Park Lights |
| F30 | 5A | Tan | Cabin Fuse / Interior Lights |
How to test a fuse
A "blown" fuse is one where the internal metal strip has melted and broken to protect a circuit from an over-current situation. You can often spot a blown fuse by visually inspecting it.
- Turn off the ignition and the affected component.
- Locate the suspect fuse using the diagrams above.
- Use a fuse puller tool (often found in the fuse box lid) or small pliers to gently remove the fuse.
- Hold the fuse up to the light. Look at the metal strip inside. If it is broken, melted, or has a dark burn mark, the fuse is blown.
- If you can't see clearly, you can use a multimeter set to continuity mode. Touch the probes to each metal tab on the top of the fuse. If it beeps, the fuse is good. If it is silent, the fuse is blown.
- Replace a blown fuse with a new one of the exact same amperage rating. Using a higher-rated fuse can cause a fire.
Common blown fuses on this vehicle
- Cigar Lighter / 12V Power Outlet Fuse (F12, F13): This is one of the most common fuses to blow. It is often caused by a faulty phone charger, an overloaded power inverter, or a coin falling into the outlet socket. Before replacing the fuse, unplug everything from the outlets and check for any foreign objects inside.
- Trailer Power Fuse (F1, F24): Issues with trailer wiring are a frequent cause. If this fuse blows, the first thing to check is the trailer plug and wiring harness on the trailer itself for corrosion, pinched wires, or shorts. A faulty trailer brake controller can also be the culprit.
- Headlight Fuses (F8, F9, F10): If a headlight fuse blows as soon as you replace it, it usually indicates a short circuit in the wiring to that headlight. Inspect the wiring harness for damage. If it blows intermittently, you may have a failing headlight bulb that is drawing too much current.
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Before you pull a fuse on the 2021 International LT
- Use the label printed on the panel cover or the owner's manual for your exact build. Layouts change with options, model year and build date, so a chart for another truck can be wrong.
- Replace a blown fuse only with the same amp rating. A larger fuse can let wiring overheat.
- A fuse that blows again right away means a short or failing component downstream. Find the cause before replacing it again.
- A good fuse doesn't prove the circuit works — relays, grounds and connectors fail too.
- Many heavy trucks have more than one power distribution point (cab, under-hood or near the batteries), and some circuits use circuit breakers instead of fuses. Some systems have 24-volt starting circuits; confirm the voltage before testing.
- Disconnect the battery before working near high-current fuses or cables.
Learn more: How fuses, relays and truck electrical systems work · Find mobile truck repair
More specs for the 2021 International LT
Oil Capacity & Filter
Capacity, weight, filter PN, drain plug torque, change interval.
Fluid Type Specs
Engine oil, coolant, ATF, diff, brake, PS, DEF — with OEM spec numbers.
Coolant Capacity & Type
Total system capacity, OEM coolant spec, flush interval, bleed tips.
Transmission Fluid & Service
Trans model, fluid spec, capacity, filter PN, service interval.
Torque Specifications
Lug nuts, drain plug, caliper, axle nut, plug, key fasteners.
Brake Pad & Rotor Specs
Pad PNs, rotor size, min thickness, caliper torque.
Tire Size & Pressure
OEM size, cold psi, bolt pattern, wheel size, TPMS.
Battery Size & Group
Group size, CCA, AGM/flooded, dimensions, reset note.
A/C Refrigerant & Oil
R-134a or R-1234yf, charge oz, PAG oil spec.
Bulb Sizes (Headlight, Tail, Fog)
Headlight, fog, tail, turn, reverse, interior.
Factory Maintenance Schedule
Service intervals by mileage, severe-duty notes, known issues.
Towing Capacity & Payload
Max tow, payload, GVWR/GCWR, hitch class by trim.
Serpentine Belt Routing & Length
Belt routing, length, rib count, OEM + aftermarket PNs.
Wheel Alignment Specifications
Camber, caster, toe ranges (front & rear), adjustability notes.
Paint Color Codes
All factory colors with paint codes, sticker location, touch-up tips.
Wiper Blade Sizes
Driver/passenger/rear blade size, attachment, OEM + cross-refs.
Spark Plug Type & Gap
Plug PN, gap, torque, interval by engine.
Transmission & Axle Gear Ratios
Trans gear ratios, axle ratios, RPO codes, tow vs MPG impact.
Key Fob Programming
DIY programming steps, FCC ID, fob PN, battery, transponder.
Same spec — other model years
Maintenance & repair guides
2021 International LT Maintenance Schedule →
Available maintenance guidance; confirm the manufacturer schedule.
Repair planning references →
Plan the scope of work; detailed procedures need configuration-matched evidence.
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