2025 Peterbilt 389 Bulb Sizes & LED Upgrade Guide

Quick reference

Location	Bulb Size	Type
Low Beam Headlight	H11	Halogen (some trims may have LED)
High Beam Headlight	HB3 (9005)	Halogen (some trims may have LED)
Fog Light	H10 (9145)	Halogen (some trims may have LED)
DRL	7443	Halogen (integrated into turn signal)
Front Turn Signal	7443NA	Amber Halogen
Rear Turn Signal	1156	Amber Halogen
Brake Light	1157	Red Halogen
Tail Light	1157	Red Halogen
Reverse Light	3156	Halogen
License Plate	194	Halogen
Front Side Marker	194	Amber Halogen
Rear Side Marker	194	Red Halogen
Dome/Map Light	578	Halogen

The 2025 Peterbilt 389, a stalwart in the heavy-duty trucking industry, continues to offer a blend of classic styling and modern engineering. While many larger trucks are transitioning to full LED lighting systems, the 389 often retains a mix of traditional halogen bulbs, particularly in its base trims. High-end trims and specific option packages, however, may feature factory-installed LED headlights, fog lights, and even some marker lights. It's always recommended to check your owner's manual or visually inspect the bulbs to confirm the exact type and size for your specific vehicle configuration.

Headlight Low Beam

The low beam headlights on the 2025 Peterbilt 389 commonly utilize H11 halogen bulbs. These provide a reliable and focused light output for general night driving. For those opting for premium lighting packages or higher trim levels, factory LED low beams may be present, offering superior brightness and a longer lifespan.

Headlight High Beam

For high beam illumination, the Peterbilt 389 typically uses HB3 (9005) halogen bulbs. These provide a powerful, far-reaching beam for maximum visibility on unlit roads. Similar to the low beams, certain configurations of the 389 might come equipped with dedicated LED high beams.

Fog Light

Fog lights, crucial for navigating adverse weather, generally employ H10 (9145) halogen bulbs on the 2025 Peterbilt 389. These bulbs produce a wide, low beam designed to cut through fog, rain, or snow. Some premium packages may include LED fog lights for enhanced performance.

Daytime Running Lights (DRL)

The DRL function on many 2025 Peterbilt 389 models is often integrated with the front turn signals, using a 7443 halogen bulb. This bulb typically operates at a lower wattage for DRL purposes and then at full power for turn signal activation. Some newer or top-tier trims may feature dedicated LED DRL strips.

Front Turn Signal

Front turn signals commonly use 7443NA (amber) halogen bulbs. These dual-filament bulbs serve both the DRL and turn signal functions. When upgrading to LED, ensure the LED bulb supports both functionalities.

Rear Turn Signal

On the rear, the turn signals typically use 1156 amber halogen bulbs. These single-filament bulbs are solely dedicated to indicating turns.

Brake Light

The brake lights on the 2025 Peterbilt 389 generally use 1157 red halogen bulbs. These are dual-filament bulbs, sharing the same housing as the tail lights.

Tail Light

Integrated with the brake lights, the tail lights also utilize 1157 red halogen bulbs. One filament illuminates for the tail light function, while the brighter filament activates for braking.

Reverse Light

For backing up, the Peterbilt 389 commonly employs 3156 halogen bulbs for its reverse lights, providing clear illumination behind the vehicle.

License Plate Light

Illuminating the license plate is typically handled by 194 halogen bulbs. These small but important bulbs ensure your license plate is visible at night.

Side Marker Lights

Both front and rear side marker lights generally use 194 halogen bulbs. The front markers are amber, and the rear markers are red, adhering to safety regulations.

Interior Dome/Map Light

Inside the cabin, the dome and map lights commonly utilize 578 halogen festoon bulbs, providing adequate illumination for the interior.

LED vs Halogen Upgrade Considerations

Upgrading from halogen to LED bulbs on your 2025 Peterbilt 389 can offer significant advantages, including brighter light output, longer lifespan, and a more modern aesthetic. However, there are several key considerations:

• CANBUS Errors: Modern vehicles, including the Peterbilt 389, often use a CANBUS (Controller Area Network Bus) system to monitor electrical circuits. LED bulbs draw significantly less power than halogens. If the vehicle's computer doesn't detect the expected power draw, it can trigger "bulb out" warnings or hyper-flashing turn signals. To prevent this, you'll typically need to install CANBUS-compatible LED bulbs or use load resistors in conjunction with standard LED bulbs. Load resistors trick the vehicle's computer into thinking a halogen bulb is still present by drawing the appropriate amount of power.
• Adapters Needed: While many LED bulbs are designed for a direct plug-and-play fit, some may require specific adapters or wiring harnesses, particularly for headlights and fog lights, to ensure proper seating and electrical connection. Always check the product specifications for compatibility.
• Beam Pattern: For headlights and fog lights, it's crucial to select LED bulbs that replicate the beam pattern of their halogen counterparts. Poorly designed LED bulbs can scatter light, creating glare for oncoming drivers and reducing your effective visibility. Look for LED bulbs specifically designed for projector or reflector housings as applicable to your 389.
• Heat Dissipation: LED bulbs generate heat, and effective heat dissipation (often through integrated fans or heat sinks) is vital for their longevity. Ensure there's adequate space behind the headlight assembly for any cooling mechanisms.

How to Replace Each Bulb (Short Tips per Location)

• Headlights (Low/High Beam): Access is usually from the rear of the headlight assembly. Twist the bulb counter-clockwise to remove, unplug the connector, and install the new bulb in reverse order. Some models may require removing the grille or fender liner for better access.
• Fog Lights: Often accessed by turning the wheel to full lock and removing a few screws from the inner fender liner to gain access to the fog light housing.
• DRL/Front Turn Signal: Located within the main headlight assembly. Access similar to headlights.
• Rear Turn Signal/Brake/Tail/Reverse Lights: Typically involves removing the tail light assembly from the exterior of the truck. Unscrew the retaining screws, gently pull the assembly out, twist the bulb sockets, and replace the bulbs.
• License Plate Lights: Usually involves removing a small plastic lens cover near the license plate with a trim removal tool or small screwdriver, then replacing the bulb.
• Side Marker Lights: These often simply twist out of their housing on the fender or side fairing.
• Dome/Map Light: Use a trim removal tool to carefully pry open the plastic lens cover on the overhead console. The festoon bulb will snap into place.

Always ensure the vehicle's ignition is off and the lights are cool before attempting any bulb replacement.

Common Lighting Issues for this Generation Peterbilt 389

While the Peterbilt 389 is known for its robust design, certain lighting issues can occasionally arise:

• Bulb Burnout: Halogen bulbs have a finite lifespan. Frequent burnouts, especially for the same bulb, might indicate voltage regulation issues or excessive vibration.
• Corrosion in Sockets: Exposure to the elements can lead to corrosion in bulb sockets, resulting in intermittent operation or complete failure. Cleaning the contacts with a wire brush or electrical contact cleaner can often resolve this.
• Wiring Harness Issues: Over time, wiring harnesses can experience fraying, pinches, or poor connections, leading to lighting malfunctions. This is more common in areas exposed to constant movement or road debris.
• Faulty Switches/Relays: Less common, but a defective headlight switch, turn signal stalk, or a faulty relay can cause lighting systems to fail.
• Trailer Wiring Conflicts: Issues with trailer wiring connections can sometimes backfeed into the truck's lighting system, causing unusual behavior like dim lights or flickering.
• DRL and Turn Signal Integration Problems: Since the DRL and front turn signals often share the same bulb, a malfunction in one can affect the other. Incorrectly installed aftermarket bulbs, especially LEDs without proper resistors, can trigger hyper-flashing or "bulb out" warnings.

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