2017 Kenworth T680 Bulb Size & LED Upgrade Guide

Quick reference

*Note: The 2017 Kenworth T680 was available with both halogen and factory LED lighting options, particularly for headlights, fog lights, and many exterior marker lights. Always verify your specific truck's configuration before purchasing replacement bulbs.

The 2017 Kenworth T680, a workhorse in the heavy-duty truck segment, offered a blend of traditional halogen lighting and advanced LED options. Understanding the specific bulb sizes for your T680 is crucial for maintenance, repairs, and upgrading your truck's illumination. This guide provides a comprehensive breakdown of common bulb sizes and important considerations for owners.

Headlights

Many 2017 T680 models came with a complex headlight assembly that could house either traditional halogen bulbs or integrated LED units from the factory. For halogen-equipped models, the low beam typically uses an H11 bulb, while the high beam uses an H9 bulb. These are common halogen sizes, offering decent light output. However, many premium trims and packages included full LED headlight assemblies, meaning the individual bulbs are not replaceable and the entire unit would need replacement if a failure occurs.

Fog Lights

Fog lights, when equipped, generally utilize an H10 bulb in halogen configurations. Similar to the headlights, some T680s were fitted with factory LED fog lights that are integrated into the bumper assembly.

DRL (Daytime Running Lights)

Daytime Running Lights on the 2017 T680 were predominantly LED-based, often integrated into the main headlight assembly. These provide enhanced visibility during daylight hours and typically do not use a replaceable bulb.

Turn Signals and Brake/Tail Lights

For both front and rear turn signals, as well as the brake and tail lights, the most common halogen bulb size is the 3157. This dual-filament bulb handles both tail light (dimmer) and brake/turn signal (brighter) functions in many applications. However, many T680s were also equipped with full LED tail light and turn signal assemblies, particularly on higher trim levels or spec'd for premium applications. These LED units are sealed and do not have serviceable individual bulbs.

Reverse Lights

Reverse lights commonly use a 921 bulb for halogen setups, providing bright white light for backing up. Again, factory LED options for reverse lights were also available, often integrated into the main tail light assembly.

License Plate and Side Marker Lights

Smaller exterior lights like the license plate and side marker lights frequently use the 194 bulb for halogen versions. These are relatively small wedge bulbs. Just like with other exterior lights, LED equivalents or factory-installed LED units are also common on the T680.

Interior Dome/Map Lights

Inside the cab, dome and map lights can vary. Common halogen sizes include the 921 (wedge style, similar to reverse lights) or 578 (a festoon-style bulb). Many trucks now feature LED interior lighting from the factory, offering a brighter and more energy-efficient solution.

LED vs Halogen Upgrade Considerations

Upgrading from halogen to LED bulbs in your 2017 Kenworth T680 can offer significant benefits, including brighter light, longer lifespan, and lower power consumption. However, it's not always a straightforward swap:

• CANBUS Errors: Modern trucks like the T680 use a CANBUS (Controller Area Network Bus) system to monitor electrical circuits. LED bulbs draw much less current than halogens, which can trick the CANBUS system into thinking a bulb is out, leading to "bulb out" warnings on your dash. Installing CANBUS-compatible LED bulbs or using load resistors/decoders is often necessary to prevent these errors.
• Adapters and Fitment: While many LED bulbs are designed to be direct replacements, some larger heat sinks on high-power LED headlights may require additional space or minor modifications for proper fitment. Ensure the LED bulb's base matches the original halogen bulb type (e.g., H11 to H11 LED).
• Beam Pattern (Headlights): For headlights, simply swapping halogen bulbs for LED replacements can sometimes result in a scattered or unoptimized beam pattern, especially in reflector housings. Look for LED bulbs specifically designed to mimic the halogen filament