2023 International LT Bulb Sizes (Headlight, Tail, Fog)

As an ASE-certified master technician who frequently works on heavy-duty commercial vehicles, I know how critical lighting is for safety and compliance. When your 2023 International LT has a light out during a pre-trip inspection, getting the right replacement bulb quickly is essential to avoid DOT violations and downtime.

Below is your comprehensive bulb size guide for the 2023 International LT. Note that fleet specifications vary wildly—many LTs come standard with premium sealed LED assemblies, while others utilize standard replaceable halogen and incandescent bulbs to lower initial fleet purchase costs.

Quick Reference

Note: The 2023 International LT offers advanced LED lighting packages (like the NiteStar® LED headlights). If your truck is equipped with these factory LEDs, the bulbs are non-replaceable, and you must replace the entire headlight or tail light assembly if a diode fails.

LED vs Halogen Upgrade Considerations

If you are upgrading a halogen fleet-spec International LT to LEDs, there are a few important considerations for Class 8 trucks:

• CANBUS Errors & Hyperflashing: Heavy-duty trucks heavily rely on body control modules (BCMs). Installing low-resistance aftermarket LED turn signals or headlights in a halogen-spec truck can trigger "bulb out" warnings on the dash or cause hyperflashing. You may need heavy-duty CANBUS decoders or load resistors.
• Beam Pattern: For H11 and 9005 headlight upgrades, ensure the LED bulb mimics the halogen filament location perfectly. Commercial DOT inspections are strict on headlight glare. Ensure your new LEDs are DOT-compliant and correctly aimed.
• Clearance and Heat: LED bulbs with cooling fans need space behind the dust cover. The International LT headlight housing has decent room, but you must ensure the heat sink doesn't rub against wiring harnesses.

How to Replace Each Bulb

• Low and High Beam Headlights: Accessing the headlight bulbs requires tilting the hood forward. The rear of the composite headlight assembly features dust caps. Twist the cap counterclockwise, unplug the wiring harness, and twist the H11 or 9005 bulb out. Do not touch the new halogen bulb glass with your bare fingers.
• Fog Lights: Located in the lower bumper, these can be accessed from underneath the front fascia. A simple quarter-turn removes the H11 bulb.
• Front Turn Signal / DRL: Accessible from behind the headlight assembly once the hood is tilted. Twist the socket out and pull the 3157 bulb straight out.
• Rear Stop/Tail/Turn/Reverse: Most LTs use standard 4-inch round rubber grommet-mounted lights at the rear of the frame or on the mudflap hangers. If you have an integrated sealed LED unit, you’ll pop the whole light out of the rubber grommet with a flathead screwdriver and unplug the 3-prong pigtail at the back.
• Side Markers / Clearance Lights: Roof cab markers and side aero-fairing markers are typically sealed LED units held in by Torx screws. Just unscrew, pull the unit, and unplug the harness.
• Interior Dome/Map: Use a plastic trim tool to gently pry the plastic lenses off the overhead console. Pull the festoon or wedge bulb straight out.

Common Lighting Issues for this Generation

The 2023 International LT is a highly reliable road tractor, but heavy-duty environments take their toll on lighting systems.

1. Wiring Harness Corrosion: Winter road salts and de-icing chemicals are notorious for wreaking havoc on the rear pigtail connectors. If a tail light fails, check for green corrosion in the 3-prong plug before buying a new light.
2. Moisture in Headlight Housings: Occasionally, the seal on the composite headlight assembly can fail, causing condensation. This will prematurely burn out halogen bulbs and can destroy factory LED driver modules.
3. Vibration Failures: Extended idling and rough highways can snap halogen filaments. Upgrading to quality LEDs or shock-resistant halogen bulbs is highly recommended for line-haul operations.

If you are dealing with persistent electrical gremlins, BCM faults, or wiring harness corrosion on your rig, don't leave it to guesswork. Find a trusted shop on Repairius.