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LED 3rd Brake Lights & T15 921 LED Bulbs

This range combines complete LED center high-mounted stop lamp (CHMSL) assemblies with T15/921 projector bulbs for replaceable upper-brake, cargo, and reverse-light positions. Options include a smoked Dodge Ram assembly with separate red brake and white cargo LEDs, plus 500-lumen-per-bulb T15/921 LEDs in 6000K white or red for compatible sockets.

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3rd Brake Lights (CHMSL) & T15 921 LED Signal Bulbs for Trucks

This collection includes LED 3rd brake lights (Center High Mounted Stop Lamps – CHMSL) and T15 / 921 LED signal bulbs, designed to improve rear signaling visibility, cargo-lighting utility, and brake-reaction awareness. These lighting components integrate with truck electrical systems and upgrade compatible factory filament lighting using solid-state LED semiconductor technology, where light is generated through electroluminescence at a p-n junction rather than a heated filament.

CHMSL lighting systems are a safety-critical signaling component. In the U.S., center high-mounted stop lamps have been required on new passenger cars since September 1, 1985, and on new light trucks, including pickups, vans, and SUVs, since September 1, 1993. Positioned higher than standard taillights, the CHMSL gives following drivers an additional, centrally located brake signal. LED light sources also reach useful output faster than conventional incandescent filament lamps.

The collection combines vehicle-specific 3rd brake light assemblies for trucks and high-output T15 / 921 LED bulbs, covering both brake signaling and auxiliary rear lighting applications.

This category includes two primary automotive lighting product types:

  1. LED 3rd Brake Light Assemblies (CHMSL)
  2. T15 / 921 CANbus LED Signal & Reverse Bulbs

Both products serve the rear signaling and visibility system of trucks and passenger vehicles.

LED 3rd Brake Light Assemblies (CHMSL)

A 3rd brake light, also called a Center High Mounted Stop Lamp (CHMSL), is a roof-mounted safety signaling light installed on the rear cab of trucks. This high-position brake signal improves rear visibility in traffic, making it easier for following drivers to detect braking.

Products in This Category

  • Dodge Ram LED 3rd Brake Lights (2009–2018) – Black/Smoke Lens
  • Ford F150 LED 3rd Brake Lights (2009–2014) – Black Housing

Replacement CHMSL assemblies rely on a correctly fitted housing gasket to seal the opening between the lamp and truck body. The Dodge Ram assembly includes a 5mm foam gasket to help seal the installation against water ingress. Aftermarket smoked-lens assemblies provide a darker exterior appearance while retaining the required red brake-light function.

Some truck CHMSL assemblies also integrate cargo-bed lighting. The Dodge Ram assembly, for example, combines 9 red LEDs for the brake lamp with 9 white LEDs for cargo illumination, providing braking and truck-bed lighting from the same housing.

T15 921 CANbus Projector LED Bulbs

The T15 / 921 LED bulb is a wedge-base automotive bulb standard commonly used in reverse lights, brake lights, and auxiliary signaling applications in 6000K white (reverse/cargo lighting). Projector-style LED bulbs include focused optical lenses, which help distribute light more evenly across the reflector housing. This improves beam intensity and visibility, especially for reverse lighting applications.

Installation & Compatibility Considerations

When installing LED CHMSL or T15 LED bulbs, several compatibility factors should be considered:

  • Vehicle-specific fitment (Ford F150, Dodge Ram, Silverado, Tacoma, etc.)
  • OEM connector compatibility for plug-and-play installation
  • Gasket sealing quality to help prevent water ingress around replacement CHMSL housings
  • CANbus or vehicle-monitoring compatibility where the electrical system monitors bulb load

Always verify vehicle year, make, and model compatibility before installing aftermarket lighting assemblies, or use the Vehicle Search tool for fitment verification.

Upgrading to LED 3rd Brake Lights with Underground Lighting

  • Higher Brake Signal Visibility

    The elevated mounting position of the CHMSL brake light ensures the braking signal is visible even when other vehicles block standard tail lights. Underground Lighting LED 3rd brake lights help maintain this improved rear visibility.

  • Faster LED Response Time

    Underground Lighting LED brake lights illuminate approximately 200 milliseconds faster than halogen bulbs, giving drivers behind more reaction time.

  • 10–20× Longer Lifespan

    Underground Lighting LED lighting systems can last 10–20× longer than traditional incandescent bulbs, reducing maintenance and replacement costs.

  • Improved Rear Vehicle Recognition

    Bright red LED brake signals from Underground Lighting help following drivers quickly identify deceleration events, improving safety in traffic.

  • Modern Truck Styling

    Underground Lighting smoked-lens brake light assemblies provide a blackout appearance that complements modern truck aesthetics.

  • Additional Cargo Bed Illumination

    Dual-function CHMSL assemblies from Underground Lighting can include white cargo lights, improving visibility when loading or unloading truck beds at night.

How to Choose the Right 3rd Brake Light Upgrade

Choose between a complete CHMSL assembly and a T15/921 bulb replacement based on what your truck actually uses and which part of the lighting system needs replacing.

  • Replace the complete assembly when the housing, lens, gasket, or integrated LED section needs an upgrade.
  • Choose a T15/921 bulb only when the factory lamp position uses a replaceable 921/T15 socket.
  • Match color to function: red for compatible brake-light positions; white for cargo or reverse-light applications.
  • Check camera configuration: trucks with a factory camera integrated into or near the CHMSL may require a different housing.
  • Inspect the sealing surface: when replacing a complete assembly, make sure the gasket sits evenly against a clean mounting surface.
  • Confirm fitment by vehicle: verify year, make, model, and bulb position before ordering.

Watch these helpful Underground Lighting videos for step-by-step guidance, product details, and real-world installation tips.

Find the Right 3rd Brake Light for Your Truck

Vehicle Part Search

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LED 3rd Brake Light FAQs

The T15 921 projector LED bulb pair is currently listed at $39.99, while the Dodge Ram LED 3rd Brake Light assembly is currently $59.99, reduced from $79.99. Complete assembly pricing varies by vehicle application, and promotions or availability can change.

When the left and right brake lights work, but the CHMSL does not, check the third-brake-light bulb or LED assembly, its connector, fuse or dedicated circuit, ground connection, and wiring. If power and ground are reaching the CHMSL connector but the lamp remains off, the bulb or assembly itself may have failed.

A compressed, damaged, incorrectly positioned, or deteriorated housing gasket can allow rain or wash water to enter between the CHMSL housing and truck body. Remove the lamp, inspect the gasket and mounting surface, and replace a damaged seal rather than relying only on tightening the mounting screws.

A required CHMSL in the U.S. must operate as a steady-burning stop lamp under FMVSS No. 108. Converting the required center stop lamp into a flashing hazard or warning lamp can create a compliance issue.

Yes. The required center high-mounted stop lamp is a red stop signal. A truck assembly may also contain separate white cargo lights, but those are a different function and should not replace the required red brake-light output.

Yes, when the vehicle's CHMSL uses a compatible T15/921 replaceable-bulb socket. The Underground Lighting T15/921 projector bulb is listed for upper third-brake-light applications, but bulb size and color still need to match the specific vehicle and lamp function.

Combination CHMSL assemblies can use separate circuits or LED sections for the red brake signal and white cargo light. When one function works but another function does not, examine the circuit, connector pins, wiring, and LED section. I do not assume that the entire assembly has lost power.

Do not assume that the entire assembly has lost power. I wonder why my LED third brake light glows faintly when it should be off. I have learned that some vehicle lighting circuits send diagnostic or monitoring currents even when the lamp is not fully switched on. An LED can respond to this small current more visibly than an incandescent filament. Confirm the bulb's electrical compatibility with the vehicle before adding resistors or modifying the circuit.

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