2020 Kenworth W900 Fuse Box Diagram & Amperage
Complete guide to the fuse and relay locations, diagrams, and amperage ratings for your 2020 KW W900.
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Quick Answer
On the 2020 Kenworth W900, you will find the main fuse and relay center inside the cab. There is also a secondary power distribution box located under the hood near the driver's side firewall.
- Main Interior Fuse Panel: Located on the passenger side of the cab, behind a kick panel or the glove box assembly. This is the primary location for most of the truck's body and cab-related fuses.
- Under-Hood Power Distribution Box: Located in the engine compartment, typically on the driver's side. This box contains high-amperage fuses and relays for engine systems and main power distribution.
Note: Always consult the diagram printed on the inside of your fuse box covers. Fuse assignments can vary depending on the specific options and powertrain your truck was built with.
Main Interior Fuse Panel (Passenger Side)
This panel houses the fuses for most of the cab's functions, including lights, gauges, radio, and HVAC.
Fuses
| Fuse # | Amp | Color | Circuit / Component Protected |
|---|---|---|---|
| F1 | 15A | Blue | Turn Signals, Hazard Lights |
| F2 | 10A | Red | Panel, Dash, & Gauge Illumination |
| F3 | 20A | Yellow | Cigar Lighter / 12V Power Port 1 |
| F4 | 20A | Yellow | Cigar Lighter / 12V Power Port 2 |
| F5 | 10A | Red | Ignition Switch Power |
| F6 | 15A | Blue | Radio, Infotainment System |
| F7 | 5A | Tan | Instrument Cluster (B+) |
| F8 | 10A | Red | Mirror Heat |
| F9 | 30A | Green | Blower Motor (HVAC Fan) |
| F10 | 10A | Red | Brake Lights |
| F11 | 10A | Red | Low Beam Headlight (Left) |
| F12 | 10A | Red | Low Beam Headlight (Right) |
| F13 | 10A | Red | High Beam Headlight (Left) |
| F14 | 10A | Red | High Beam Headlight (Right) |
| F15 | 15A | Blue | Fuel Pump |
| F16 | 10A | Red | Parking / Marker Lights |
| F17 | 20A | Yellow | Wipers |
| F18 | 15A | Blue | ABS Control Unit (Key Power) |
| F19 | 10A | Red | Airbag / SRS Module |
| F20 | 15A | Blue | A/C Compressor Clutch |
| F21 | 30A | Green | Trailer Marker Lights |
| F22 | 30A | Green | Trailer Brake Controller Power |
| F23 | 10A | Red | ECM / PCM (Key Power) |
| F24 | 5A | Tan | Sleeper Panel Power |
Relays
| Relay # | Circuit Controlled |
|---|---|
| R1 | Ignition Main |
| R2 | Blower Motor |
| R3 | A/C Clutch |
| R4 | Low Beam Headlights |
| R5 | High Beam Headlights |
| R6 | Horn |
Under-Hood Power Distribution Box
This box contains high-amperage mega-fuses and critical relays for engine and chassis systems.
| Fuse # | Amp | Color | Circuit / Component Protected |
|---|---|---|---|
| M1 | 175A | - | Main Starter Feed |
| M2 | 125A | - | Main Cab Power |
| M3 | 60A | - | ABS System Power |
| M4 | 40A | Orange | ECM / PCM Main Power |
| M5 | 50A | Red | Engine Aftertreatment System |
| M6 | 30A | Green | Fuel Heater |
| Relay # | Circuit Controlled |
|---|---|
| R1 | Starter Relay |
| R2 | ECM Main Power Relay |
| R3 | Fuel Pump Relay |
| R4 | Engine Fan Override |
How to Test a Fuse
A blown fuse can cause an entire circuit to fail. Luckily, checking a fuse is a simple process.
- Turn Off the Ignition: Before checking any fuses, turn the truck completely off.
- Locate the Fuse: Using the diagrams above, find the fuse for the component that is not working.
- Remove the Fuse: A fuse puller tool (often found in the fuse box lid) makes this easy. If you don't have one, small needle-nose pliers will work carefully.
- Visual Inspection: Hold the fuse up to the light. Inside a "good" fuse, you will see an intact, S-shaped or straight metal wire. In a "blown" fuse, this wire will be broken or melted. You may also see a black or hazy discoloration inside the plastic.
- Test with a Multimeter (Optional but Recommended): For a more definitive test, set a multimeter to the continuity setting (it looks like a sound wave or diode symbol). Touch the probes to each of the two metal tabs on top of the fuse. If the multimeter beeps, the fuse is good. If it remains silent, the fuse is blown and needs to be replaced.
- Replace the Fuse: If the fuse is blown, replace it with a new fuse of the exact same amperage rating. Using a higher-rated fuse can cause a fire hazard by allowing too much current through the circuit.
Common Blown Fuses on the 2020 Kenworth W900
- Cigar Lighter / 12V Power Port: These fuses (F3, F4) are frequently the first to blow. This is almost always caused by a faulty or cheap phone charger, a bad plug on a CB radio or other accessory, or a coin falling into the socket. Before replacing the fuse, unplug everything from the power ports and inspect the sockets for foreign objects.
- Trailer Lights: Fuses related to trailer lighting (F21, F22) are common failure points. The issue is rarely the truck itself. The problem is usually a short in the trailer wiring, a corroded trailer-side plug, or a faulty light on the trailer. If a trailer light fuse blows, the very first thing to check is the trailer you just hooked up to.
- Headlights: While a single burnt-out headlight is usually just a bad bulb, if both low beams or both high beams stop working at once, check the corresponding fuses (F11-F14) and relays (R4, R5) first. This is much quicker and cheaper than replacing both bulbs as a first step.
If a fuse blows repeatedly, this indicates an underlying short circuit that needs to be diagnosed and repaired by a qualified technician.
If you're struggling with electrical issues or any other truck repair, use Repairius to find a trusted and qualified heavy-duty shop in your area. '''
Before you pull a fuse on the 2020 Kenworth W900
- 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 2020 Kenworth W900
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
2020 Kenworth W900 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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