Brake Light Switch

Replace the brake light switch located on the brake pedal assembly to restore brake light operation and ensure proper communication with vehicle safety systems including cruise control and transmission shift interlock.

Warnings

Tools required

Parts

• Brake light switch × 1 — A0015456409 or equivalent OEM

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn ignition to OFF position and remove key from ignition
3. Open driver's door and adjust seat to full rearward position for maximum working room
4. Remove lower dash panel below steering column if equipped (typically held by plastic clips and possibly 10mm fasteners)
5. Allow eyes to adjust to low-light conditions or position work light to illuminate brake pedal assembly area
6. Locate brake light switch on brake pedal bracket - it is typically mounted above the brake pedal arm with a plunger that contacts the pedal

Procedure

1. 1

   Disconnect electrical connector from brake light switch
   Locate the electrical connector on the brake light switch body. Press the release tab on the connector and pull firmly straight away from the switch. The connector may be stiff due to age. Do not pull on wires - grasp the connector body. If access is limited, a flat blade screwdriver can carefully release the locking tab.
2. 2

   Identify switch mounting method
   Mercedes brake light switches use either a twist-lock bayonet mount or a sliding clip mount. Examine the switch body: bayonet mounts have alignment marks and rotate approximately 30-45 degrees to release; clip mounts have side tabs and pull straight out. On 2007-2013 S65 AMG, the most common type is the twist-lock bayonet style.
3. 3

   Remove old brake light switch
   For bayonet mount: Rotate switch counterclockwise (when viewed from behind) approximately 30-45 degrees until it releases from the mounting bracket, then pull straight out. For clip mount: Squeeze side tabs together and pull switch straight out from bracket. Note the installed depth and plunger position for reference during installation. The brake pedal may move slightly forward when switch is removed due to loss of contact point.
4. 4

   Inspect mounting bracket and pedal arm
   Check the mounting bracket for cracks or damage. Inspect the brake pedal arm contact point for wear or deformation. Clean any dirt or debris from the mounting bracket opening. Verify the pedal return spring is functioning properly and pedal returns fully to rest position without binding.
5. 5

   Prepare new brake light switch
   Compare new switch to old unit to verify correct replacement part. Check that plunger moves freely and returns under spring pressure. Most replacement switches come pre-adjusted, but verify plunger is in the fully extended position before installation. Do not adjust plunger position unless specifically required by installation instructions.
6. 6

   Install new brake light switch
   For bayonet mount: Align switch tabs with bracket slots and push switch straight in until fully seated against bracket, then rotate clockwise 30-45 degrees until it locks into place with a distinct click. For clip mount: Push switch straight into bracket until side tabs click into locked position. Ensure switch is fully seated and secure. The plunger should contact the brake pedal arm with pedal at rest.
7. 7

   Verify plunger contact and adjustment
   With pedal at rest position, verify the brake pedal arm is holding the switch plunger compressed approximately 2-4mm. There should be light but definite contact. If plunger has no contact or excessive compression (more than 5mm), switch position may need adjustment. Most switches are self-adjusting: with switch loosely installed, press brake pedal fully, release pedal, then fully seat and lock switch - this sets proper gap automatically.
8. 8

   Reconnect electrical connector
   Push electrical connector onto brake light switch terminals until it clicks securely into locked position. Gently tug on connector to verify it is fully latched. Ensure wiring is routed away from brake pedal pivot points and moving components.
9. 9

   Test brake light operation
   Turn ignition to position II (ON) without starting engine. Have assistant observe brake lights while you press brake pedal, or observe reflection in garage door/window. Verify both brake lights illuminate immediately when pedal is pressed and extinguish completely when pedal is released. Test multiple times to confirm consistent operation.
10. 10

    Test integrated safety systems
    With engine running, verify cruise control can be set and cancels immediately when brake pedal is pressed. Verify transmission shifts out of Park only when brake pedal is depressed. Check that brake assist system indicator (if equipped) does not show faults. These systems rely on brake light switch signal and must function properly.

Reassembly

1. Reinstall lower dash panel below steering column, ensuring all clips are fully seated and any fasteners are tightened securely
2. Return driver's seat to normal operating position
3. Clear any brake system fault codes stored in vehicle memory using diagnostic scanner if available

Verification

• With ignition ON, verify both brake lights illuminate when pedal is pressed and turn off when released
• Verify center high-mount stop light (third brake light) also functions properly
• Confirm transmission will not shift out of Park without brake pedal depressed
• Test that cruise control (if used) disengages immediately when brake pedal is touched
• Check instrument cluster for any new warning lights or fault messages related to brake system
• Perform test drive to verify brake lights function properly and all integrated safety systems operate normally
• Have another person verify brake lights are visible and functioning before returning vehicle to service

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