Brake light not working properly

2001 MERCEDES BENZ S430
208,000 MILES • V8 • 2WD • AUTOMATIC
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TERRENCEJ
  • MEMBER
  • 2 POSTS
When i press the brake pedal my driver side brake light comes on then goes off.
Mar 22, 2019 at 9:44 AM
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JOETECHPRO
  • CERTIFIED EXPERT
  • 705 POSTS
Hey TERRENCEJ,

This may sound obvious but have you replaced the bulb?

When the filament heats up it can sometimes cause a break in the connection and as it cools it reconnects.

Please if you haven't done already replace the bulb and retest.

Regards, Joe
Mar 23, 2019 at 1:16 PM
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TERRENCEJ
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  • 2 POSTS
Yes, i have replaced all the bulbs and changed the tail lights with new ones. also the brake light that is acting up is ran off a circuit board not a bulb.
Mar 23, 2019 at 1:34 PM
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JOETECHPRO
  • CERTIFIED EXPERT
  • 705 POSTS
Hey TERRENCEJ,

I have attached the wiring diagram for the rear lights.

If the brake unit portion is an LED and you have already replaced the unit then you will have an issue with either power or ground to the brake light unit or a problem with the SAM module for the rear.

To begin i would get someone to operate the brake light and check for voltage between pin 3 and pin 7 on the light unit connector.

You will need a multimeter for this testing.

Let me know what reading you get when it initially comes on and then what it is with the pedal depressed but no light output.

Hope that helps.

The wiring diagram is attached to this message.

Regards, Joe
Mar 23, 2019 at 5:47 PM