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Brake Light Working Intermittent
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Posted 3/27/2018 7:52 PM
Rangek1d
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Date registered: Feb 2018
Location: Calgary, Canada
Vehicle(s): 03 G55 Brilliant Silver
Posts: 25
25
Brake Light Working Intermittent

I've got an error up on the dash, Right Brake Light. I opened it up and all the bulbs are fine. I asked another person to watch the rear as I hit the break pedal, apparently the brake lights are not working properly. I'll describe the situation in more detail below:

I've got 3 brake lights because the previous owner bolted a brabus style spoiler on the back.....
So the brake light in the tail lights are operating intermittently when I press the pedal. The spoiler brake light seems to flash. The brake light in the window is fairly dim and also working intermittently.

To fix this, do I install a new brake light switch? Or a new brake light harness? I'm not sure where to even start. Any and all advice is appreciated.

Thanks

Edited by Rangek1d 3/27/2018 7:54 PM
#238810
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Posted 3/28/2018 1:05 AM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
2000
RE: Brake Light Working Intermittent

Switch places with your observer.  Watch the lights carefully from a distance. 

If the lights go on and off at the same time, then you have a switch or possibly a wiring problem. 

If they go on and off independently then the problem probably lies in the lights or light sockets, small chance of wiring.

#238813 - in reply to #238810
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Posted 3/28/2018 10:32 AM
Rangek1d
Member


Date registered: Feb 2018
Location: Calgary, Canada
Vehicle(s): 03 G55 Brilliant Silver
Posts: 25
25
RE: Brake Light Working Intermittent

AlanMcR - 3/27/2018 11:05 PM

Switch places with your observer.  Watch the lights carefully from a distance. 

If the lights go on and off at the same time, then you have a switch or possibly a wiring problem. 

If they go on and off independently then the problem probably lies in the lights or light sockets, small chance of wiring.



That sounds like a plan, thanks Alan, I'll give that a try soon and update the thread, on a side note I did see that the spoiler brake light was wired up with the right tail light wiring, and the error on the dash also indicates a right brake light failure. Coincidence? I think not!
#238815 - in reply to #238813
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Posted 3/28/2018 12:33 PM
ychung
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Date registered: Aug 2015
Location: SO CAL
Vehicle(s): 2004 G500, 2014 ML350, 2008 S550
Posts: 196
100
RE: Brake Light Working Intermittent

Why don't you disconnect the wires to the spoiler brake light first and go from there?
#238816 - in reply to #238810
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Posted 3/29/2018 1:28 PM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
2000
RE: Brake Light Working Intermittent

Too much electrical loading on the right bulb.  Virtually all the bulbs are monitored by the lighting computer(s).  Too much or too little current will definitely irritate the system.  In turn, the system may stop trying to light up the bulb to prevent melting a connector/wire.

Try installing LEDs w/o load resistors in the add-on part.  Alternatively, connect it to the 3rd brake light instead.  I have read that it is not monitored as closely.



Edited by AlanMcR 3/29/2018 1:30 PM
#238825 - in reply to #238815
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Posted 3/29/2018 6:30 PM
NHDave
Extreme Veteran




Date registered: Dec 2013
Location: Seacoast NH.
Vehicle(s): 2004 AMG
Posts: 464
300
Re: Brake Light Working Intermittent

By any chance..have you or anyone installed brighter bulbs or LED's for stop lights. As AlanMcR mentioned..too little or too much bulb draw can cause the same issue.

Edited by NHDave 3/29/2018 6:31 PM
#238826 - in reply to #238810
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Posted 4/3/2018 7:59 PM
fernweh



Date registered: Apr 2006
Location: Calabasas, CA - Centenario, BCS - Luebeck, Germany
Vehicle(s): Few Mercedes-Benz, a Toyota Amphibious and a Vespa
2000
Re: Brake Light Working Intermittent

Our friend Harald used to have the same problems, the bulbs are always ok, but once in a while, one side did not work.
I did traced it to the SAM unit in the center console, not working correctly.....
Due to no parts availability in Baja Sur, I just wired it to the third brake light, which is not monitored at all.

Will ask him tomorrow at lunch, if he still lives with that fix, from a few years ago.
#238852 - in reply to #238826
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Posted 4/8/2018 2:52 AM
Rangek1d
Member


Date registered: Feb 2018
Location: Calgary, Canada
Vehicle(s): 03 G55 Brilliant Silver
Posts: 25
25
Re: Brake Light Working Intermittent

Sorry for late update, so all the lights (including spoiler brake light) would basically dim together, these symptoms were occruing as the key in the ignition was in second notch without engine on. After having the engine running and the alternator kicking in, the brake lights were coming on much stronger, however the right tail lamp brake light is still not showing any signs of life. There is a foot of snow outside right now, as soon as the weather clears I'm going to remove that monstrosity of a spoiler and with it the connection it has to the right brake light. Dear lord I hope it has nothing to do with the SAM, that sounds like a a big budget problem that I don't have time or money for at this moment considering I might have to do a timing chain job.
#238890 - in reply to #238810
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