Third Brake Light

Replace the center high-mounted stop lamp (third brake light) assembly on the rear cab of the 2007 Ram 3500.

Warnings

Tools required

Parts

• Center high-mounted stop lamp assembly (CHMSL) × 1 — Use OEM specification or compatible aftermarket
• Replacement bulb (if bulb only) × 1 — 921 wedge bulb or LED assembly depending on model

Preparation

1. Park vehicle on level surface and turn ignition OFF
2. Allow any exterior lighting to cool if recently operated
3. Position step stool or ladder to safely access the rear cab roof area above the rear window
4. Determine if complete assembly replacement is needed or bulb replacement only

Procedure

1. 1

   Access the third brake light assembly
   Safely position yourself to access the center high-mounted stop lamp on the rear of the cab, just above the rear window. The assembly is mounted at the rear of the cab above the rear window on 2007 Ram 3500 models; verify the exact mounting method (screws vs. retaining clips) for your specific configuration before proceeding.
2. 2

   Remove mounting screws
   Inspect the assembly to determine the retention method. If secured by screws, use the appropriate screwdriver to remove them; if retained by clips or tabs, use a plastic trim tool to release them. Support the assembly with one hand while removing the final fastener. These screws are typically visible on the front face of the lens assembly or may be accessed from underneath depending on the specific assembly design. Support the assembly with one hand while removing the final screw.
3. 3

   Pull assembly away from mounting surface
   Gently pull the brake light assembly away from the cab mounting surface. If the assembly is sealed with adhesive or has clips, use a plastic trim tool to carefully release any retaining clips. Be careful not to let the assembly drop as you separate it from the mounting surface.
4. 4

   Disconnect electrical connector
   Locate the electrical connector at the rear of the lamp assembly. Press the release tab on the connector and carefully pull the connector apart to disconnect power from the lamp assembly. On some models, you may need to rotate the bulb socket counterclockwise to remove it from the housing.
5. 5

   Remove old assembly or bulb
   If replacing the entire assembly, set the old unit aside. If replacing only the bulb, remove the bulb socket from the housing by rotating counterclockwise, then pull the wedge-style bulb straight out from the socket. Inspect the socket for corrosion or burned contacts.
6. 6

   Install new bulb or prepare new assembly
   If installing a new bulb only, insert the replacement 921 wedge bulb into the socket without touching the glass with bare fingers. If installing a complete new assembly, verify the new unit matches the original and that the electrical connector is compatible. Clean any old adhesive or debris from the mounting surface on the cab.
7. 7

   Connect electrical connector
   Reconnect the electrical connector to the new lamp assembly or reinstall the bulb socket into the housing by rotating clockwise until it locks in place. Ensure the connection is firm and fully seated.
8. 8

   Test brake light operation
   Before fully securing the assembly, turn the ignition to the ON position and have an assistant press the brake pedal, or use a brake pedal depressor. Verify the third brake light illuminates properly. If the light does not function, recheck all connections and verify bulb installation.
9. 9

   Reinstall assembly to cab
   Position the brake light assembly back onto the cab mounting surface, ensuring any alignment pins or clips are properly engaged. If the assembly uses an adhesive gasket, ensure it is properly positioned to create a weather seal.
10. 10

    Secure mounting screws
    Reinstall the retaining fasteners (screws or clips) as removed during disassembly, tightening any screws snugly but not overtightening, as this may crack the plastic lens housing. Tighten screws snugly but do not overtighten, as this may crack the plastic lens housing. Ensure the assembly is secure and properly sealed against the mounting surface.

Reassembly

1. Verify all screws are tightened and the assembly is secure with no gaps that would allow water intrusion
2. Wipe down the lens with a clean shop towel to remove any fingerprints or debris

Verification

• With ignition ON, press and release the brake pedal multiple times while observing the third brake light to confirm it illuminates consistently with each application
• Verify the light turns OFF completely when the brake pedal is released
• Inspect the mounting area for proper sealing and ensure no water can enter the electrical connections
• Test brake lights again after closing all doors and with vehicle in normal operating condition before driving

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