2021 Kenworth T680 Bulb Size Guide

Quick Reference: 2021 Kenworth T680 Bulb Sizes

Note: Higher trim levels of the 2021 Kenworth T680 may feature full LED assemblies for headlights and tail lights, which are not designed for individual bulb replacement.

LED vs. Halogen Upgrade Considerations

Upgrading your Kenworth T680 to LED bulbs can significantly improve visibility and bulb lifespan. However, there are a few things to keep in mind:

• CANBUS Errors: The T680's computer system monitors the electrical current of the lighting circuits. Since LEDs draw less power than halogens, the system may mistakenly register a "bulb out" error. To prevent this, you'll need to install CANBUS-compatible LED bulbs or add a resistor to the circuit.
• Adapter Plates: Some LED headlight conversion kits may require an adapter plate to fit securely in the T680's headlight housing. Check with the LED bulb manufacturer to see if an adapter is needed for your specific model.

How to Replace Each Bulb

• Headlights & Fog Lights: Access the headlight and fog light bulbs by opening the hood and locating the back of the headlight assembly. Twist the bulb socket counter-clockwise to remove it, then gently pull the old bulb out and insert the new one.
• Turn Signals, Brake Lights, & Tail Lights: These bulbs are located in the rear tail light assembly. To access them, remove the screws holding the assembly in place and carefully pull it away from the truck. The bulb sockets are on the back of the assembly.
• License Plate Light: The license plate light is typically housed in a small plastic lens above the license plate. Use a small screwdriver to pry the lens off and access the bulb.
• Side Marker & Interior Lights: These bulbs are generally easy to access. The side marker lens can be popped out with a screwdriver, and the interior dome/map light covers can usually be removed by hand.

Common Lighting Issues for this Generation

The 2021 Kenworth T680 is a reliable truck, but like any vehicle, it can experience occasional lighting problems. Some common issues include:

• Premature Bulb Burnout: This can be caused by a number of factors, including a faulty voltage regulator or excessive vibration.
• Flickering Lights: Flickering lights are often a sign of a loose electrical connection. Check the bulb sockets and wiring for any signs of corrosion or damage.
• One Light Out: If a single light is out, the most likely culprit is a burned-out bulb. However, it could also be a blown fuse or a wiring issue.

If you're not comfortable performing these repairs yourself, it's always best to consult a professional.

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