2016 Kenworth W900 Bulb Sizes (Headlight, Tail, Fog)

The 2016 Kenworth W900 is an iconic piece of American trucking history. While its classic long-hood design remains timeless, its lighting system bridges the gap between old-school sealed beams and modern heavy-duty illumination. As an ASE-certified master technician, I’ve worked on countless W900s, and upgrading or replacing lighting on these rigs is one of the most common maintenance tasks.

Whether you're running the standard halogen setup or want to upgrade your rig to full LED for those long overnight hauls, knowing your exact bulb sizes is crucial to keeping your truck DOT-compliant and safe on the road.

Quick reference

Note: Many 2016 Kenworth W900 models come from the factory with sealed LED units for markers, tail lights, and cab lights. If your truck has standard incandescent fixtures, refer to the sizes below. Headlights are traditionally 4x6 inch sealed beam units.

LED vs halogen upgrade considerations

When upgrading a 2016 Kenworth W900 from standard halogen or incandescent bulbs to LEDs, there are a few heavy-duty specific considerations to keep in mind:

• Sealed Beam Conversions: The W900 traditionally uses four 4x6 inch sealed beam headlights. Upgrading to LED means replacing the entire housing rather than just a bulb. Ensure you choose DOT-approved 4x6 LED headlights with standard H4 pigtail connections.
• Flasher Relays: Upgrading turn signals to LED will almost certainly cause "hyper-flashing" because LEDs draw significantly less power. You will need to upgrade your truck's mechanical flasher relay to an LED-compatible electronic flasher relay to normalize the blink rate.
• Voltage Spikes: Heavy-duty alternators can sometimes produce voltage spikes. When purchasing aftermarket LED modules for cab lights or tail lights, ensure they are rated for 12V-24V wide-range operation to prevent premature burnout.
• Sealed Housings: For markers, brake, and tail lights, it is often more reliable to install complete sealed LED fixtures (like standard 4-inch round grommet-mount lights) rather than putting LED replacement bulbs into old, potentially corroded incandescent housings.

How to replace each bulb

Here are a few quick tips for tackling bulb replacements on your W900:

• Headlights (Low and High Beams): Removing the headlights on a W900 requires removing the stainless steel bezel around the light assemblies. Usually, this involves a few Phillips or Torx screws. Once the bezel is off, remove the retaining ring holding the sealed beam, pull it forward, and unplug the H4 connector.
• Fog Lights: These are typically mounted in or under the front bumper. If you have the halogen H3 housings, access the back of the housing, remove the rubber dust boot or rear cap, unclip the retaining wire, and swap the bulb.
• Front Turn Signals: Often mounted on the fenders as pedestal lights. If you are replacing the bulb inside, simply unscrew the amber lens. If upgrading to sealed LEDs, you will need to unbolt the pedestal from the fender and splice or plug in the new unit.
• Rear Tail/Brake/Turn & Reverse: Most modern W900s utilize standard 4-inch round rubber grommet-mounted lights on the rear light bar. To replace these, use a flathead screwdriver to gently pry the sealed light unit out of the rubber grommet, unplug the 3-prong pigtail, and push the new one in.
• Cab Marker Lights: Accessing the classic "watermelon" or torpedo cab lights requires removing the exterior screws holding the lens. Inspect the gasket when replacing the 194 bulb; if the gasket is cracked, replace it to prevent water intrusion into the cab.
• Dome/Map Lights: Carefully pry the plastic covers off the interior overhead console with a non-marring trim tool. The festoon (211-2) or bayonet (1003) bulbs will pop right out.

Common lighting issues for this generation

The 2016 W900 is a robust workhorse, but its electrical and lighting systems face harsh environments.

• Corroded Pigtails: The 3-prong pigtails on the rear light bars are notorious for collecting road salt and moisture. If a new tail light doesn't work, apply dielectric grease to a replacement pigtail.
• Grounding Issues: Heavy-duty trucks vibrate extensively. If you notice a headlight or group of marker lights dimming or flickering, check the chassis ground straps. A loose ground is the culprit 90% of the time.
• Cab Light Leaks: Sun exposure degrades the rubber gaskets on the roof cab lights, leading to shorted bulbs and water dripping onto the headliner. Always replace the seals when changing cab light bulbs.

Maintaining the lighting on your rig is essential for safety, compliance, and looking good on the highway. If you're dealing with persistent wiring issues or want a professional to handle a complete LED conversion, don't leave it to chance. Find a trusted shop on Repairius.