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Third Brake Light Replacement
 
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Pelican Technical Article:

Third Brake Light Replacement

Tom Morr

Time:

30 minutes30 mins

Tab:

$180

Talent:

*

Tools:

Small Phillips screwdriver, small flathead screwdriver, possibly needle-nose pliers

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

Replacement light assembly

Hot Tip:

Don't attempt to pry the lens away from the trunk

Performance Gain:

Legal brake light illumination

Complementary Modification:

Replace license plate light bulbs if necessary

LED technology for brake lights offers advantages over traditional incandescent bulbs. First and foremost, LEDs are brighter at lower amperage draw. LEDs also "fire" quicker, reaching maximum illumination faster than incandescent bulbs. Even a millisecond of extra warning can be beneficial for brake lights, particularly for the CHMSL (center high-mounted stop light).

Cost is the trade-off. LEDs require a circuit board. (The R170's third brake light has 24 LEDs.) And while replacing individual diodes on the circuit board is certainly possible, the focus here is on swapping out the entire unit. Pelican Parts sells the complete assembly (170-820-05-56-MBZ, Additional Stop Light), which includes the lens, diode housing/circuit board, and reflector. The tinware isn't inexpensive, but there's no need to pay someone to install it.

The cover plate inside the trunk lid must be removed.
Figure 1

The cover plate inside the trunk lid must be removed. Three plastic rivets (arrows) hold it on. Gently pry out the rivets' center pins with a flathead screwdriver, then remove their bodies.

Pull the plug (arrow) out of the diode housing.
Figure 2

Pull the plug (arrow) out of the diode housing.

The diode housing has tabs (arrows) that secure it to the reflector.
Figure 3

The diode housing has tabs (arrows) that secure it to the reflector. A small flathead screwdriver is helpful for depressing these tabs in order to lift off the diode housing.

The lens is held in place on the trunk by molded-in clips (arrows) that hook on the reflector housing.
Figure 4

The lens is held in place on the trunk by molded-in clips (arrows) that hook on the reflector housing. Beginning at one end, gently pinch the clips, with a small screwdriver or needle-nose pliers if necessary, until their barbs clear the reflector's shoulders.

Gently lifting the lens as you go helps the fragile clips slide through the slots in the reflector.
Figure 5

Gently lifting the lens as you go helps the fragile clips slide through the slots in the reflector.

With the lens out of the way, the three small Phillips screws (arrows) that mount the reflector are accessible.
Figure 6

With the lens out of the way, the three small Phillips screws (arrows) that mount the reflector are accessible.

Once unscrewed, the reflector can be removed from inside the trunk's lid.
Figure 7

Once unscrewed, the reflector can be removed from inside the trunk's lid.

OE replacement third brake lights are sold as an assembly, which includes the LED housing (top), reflector (center) and lens with sealing gasket (bottom).
Figure 8

OE replacement third brake lights are sold as an assembly, which includes the LED housing (top), reflector (center) and lens with sealing gasket (bottom). Installation reverses the disassembly.

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Comments and Suggestions:
Steve Comments: Thank you very much Nick for your help I really appreciate it I will do
September 22, 2015
  Followup from the Pelican Staff: No problem. Let me know how it works out. - Nick at Pelican Parts  
Steve Comments: Hello I recently had my 98 SLK 230 repainted when they repainted the car live in the trunk they remove the right to do so now I'm leaking water inside the trunk from the light was wondering if you could recommend something I can use to seal this
September 19, 2015
  Followup from the Pelican Staff: Replace the seal for the light. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 

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