2019 Kenworth W900 Bulb Sizes

Quick Reference: 2019 Kenworth W900 Bulb Sizes

The 2019 Kenworth W900, a legendary workhorse known for its rugged reliability and classic styling, utilizes a mix of bulb types depending on the trim and optional lighting packages. While many W900s came equipped with traditional halogen lighting, some were available with High-Intensity Discharge (HID) low beams for improved nighttime visibility. LED options were less common as original equipment in 2019 but are a popular aftermarket upgrade.

Low Beam

For the low beam headlights, the most common halogen bulb size is the H11. However, some W900s equipped with a premium lighting package may feature D2S HID bulbs, identifiable by their brighter, whiter light and often coupled with projector-style housings. It's crucial to check your specific truck's headlight assembly to determine whether you have halogen or HID bulbs before purchasing replacements.

High Beam

High beam headlights typically use H7 or H9 halogen bulbs. Again, a visual inspection of your existing bulbs or your owner's manual will confirm the exact size.

Fog Light

Fog lights on the 2019 W900 commonly take an H10/9145 halogen bulb. These are designed to provide a wide, low beam of light to cut through fog and improve visibility in adverse weather conditions.

Daytime Running Lights (DRL) & Front Turn Signals

Many W900 models combine the Daytime Running Light (DRL) and front turn signal functions into a single bulb, typically a 3157 or 7443. These are dual-filament incandescent bulbs, with one filament for the DRL and the other for the brighter turn signal.

Rear Turn Signal, Brake Light, Tail Light, and Reverse Light

The rear lighting on the W900 often utilizes the versatile 3157 incandescent bulb for the rear turn signals, brake lights, tail lights, and reverse lights. This common bulb type simplifies replacement and stocking for fleet managers and individual owners.

License Plate and Side Marker Lights

Smaller auxiliary lights such as the license plate lights and side marker lights typically use the 194 incandescent bulb. These are compact bulbs that provide sufficient illumination for their respective functions.

Dome/Map Lights

Inside the cabin, the dome light commonly uses a 578 fuse-style incandescent bulb, providing general illumination. Map lights, if separate, often use a 194 bulb.

LED vs Halogen Upgrade Considerations

Upgrading from halogen to LED bulbs is a popular choice for W900 owners looking for brighter, longer-lasting, and more energy-efficient lighting. However, several factors need to be considered:

• CANBUS Errors: Modern vehicles, including the W900, use a CANBUS (Controller Area Network Bus) system to monitor electrical components. LED bulbs draw significantly less power than halogens, which can trick the CANBUS system into thinking a bulb is out, leading to "bulb out" warnings on the dashboard or hyper-flashing turn signals. CANBUS-compatible LED bulbs or load resistors are often required to prevent these issues.
• Beam Pattern: Not all LED bulbs are created equal. Poorly designed LED headlights can scatter light inefficiently, creating glare for oncoming drivers and reducing your usable light output. Look for LED bulbs designed to mimic the filament placement of their halogen counterparts or consider projector-style LED retrofits for the best beam pattern.
• Heat Dissipation: LEDs generate heat, but unlike halogens which radiate it forward, LEDs often dissipate heat from their base. Many high-quality LED bulbs feature integrated cooling fans or heat sinks. Ensure there's adequate space in the headlight housing for proper heat dissipation to prevent premature LED failure.
• Adapters: Some LED kits may require specific adapters or wiring harnesses to connect seamlessly with the W900's existing electrical connectors.

How to Replace Each Bulb (Short Tips)

• Headlights (Low/High Beam): Access is usually from behind the headlight assembly in the engine bay. Twist to remove the bulb socket, then replace the bulb. For HID D2S bulbs, specialized knowledge may be required due to high voltage. Always disconnect the battery before working on electrical components.
• Fog Lights: Often accessible from underneath the bumper or by removing an inner fender liner. Twist and pull to remove the socket.
• Front Turn Signal/DRL: Typically accessed from within the engine bay, behind the headlight assembly. Twist to remove the socket.
• Rear Lighting (Turn, Brake, Tail, Reverse): Usually accessed by removing the tail light lens assembly from the exterior (multiple screws) or from behind the housing in the truck frame. Twist the socket to remove.
• License Plate Lights: Usually accessed by removing a few screws holding the light housing.
• Side Marker Lights: These often simply snap into place or are held by a single screw. Gently pry or unscrew to access the bulb.
• Dome/Map Lights: Carefully pry off the lens cover with a plastic trim tool or small flathead screwdriver. The bulbs typically push in or twist into their sockets.

Common Lighting Issues for this Generation

For the 2019 Kenworth W900, common lighting issues are often related to the demanding environment these trucks operate in. Vibrations can lead to premature filament failure in incandescent bulbs. Corrosion in bulb sockets, especially in older trucks or those exposed to harsh weather, can cause intermittent lighting or complete bulb failure. Electrical shorts, though less common, can also occur. Regular inspection of bulbs and connections, especially during preventative maintenance, can help catch and address these issues before they become major problems. If you're experiencing frequent bulb outages or electrical gremlins, it's worth investigating the wiring and socket integrity.

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