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Discussion Starter · #1 ·
Hey guys,
My red warning light which is near the rear of the dash indicator came on. At first I thought the tail lights were out. All the lights are fine and come on. Any idea why the red warning light would come on?
 

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Discussion Starter · #7 ·
Someone on .org found the problem. Apparently, BMW has a back up brake light. What happens is if the real brake light burns out, the back up turns on. The back up is considerably dimmer than the real one. You learn something new every day:)
 

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you know i read something about that in the manual...but i didn't believe it. :)

and after seeing my coworkers car with the burnt out tail light u can definitely tell it's gone. no brake lights on the left side. don't know which is the case...redundant or not?

Maximus said:
Someone on .org found the problem. Apparently, BMW has a back up brake light. What happens is if the real brake light burns out, the back up turns on. The back up is considerably dimmer than the real one. You learn something new every day:)
 

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Maximus said:
Someone on .org found the problem. Apparently, BMW has a back up brake light. What happens is if the real brake light burns out, the back up turns on. The back up is considerably dimmer than the real one. You learn something new every day:)
Strictly speaking, it's not a backup. Rather, BMWs like virtually every other car uses a dual-filament bulb, one filament high wattage the other low. The former lights up when you press the brake pedal, the latter lights with you turn on your running lights (usually at night). Either filament can fail (burn out) without affecting the other. Failure most commonly happens with the high-power filament because it gets used the most.

Now, in old cars where just about everything in the electrical system was hardwired, a failed brake filament would mean no brake light, but the running lights would still work. However, with modern cars, BMW's in particular, activation of lighting circuits is done by computer. So, when the brake filament burns out, the car's electronics can substitute energizing the running light filament when the brake pedal is pressed. The result is a dimmer light when braking, but it's better than nothing. Good safety feature.

Dave
 
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