my 08 3rd brake lite has not worked since I got the car, even after changing the bulb. I saw 3 other Smarts today with the same lite inop and was wondering if there is a common problem on these cars and if so what would it take to fix it.
Mine was replaced under warranty as well for moisture collecting inside. I was crossing my fingers that they didn’t blame the Brabus spoiler I had installed right on top of that area, and luckily they didn’t.
That bulb burned out on mine with less than 14k miles. I replaced it with a SYLVANIA LED, which I found made a pinkish color and light distribution that is illegal, so I got a Brabus LED option, part # A 451 906 49 00, to replace the lamp.
Check the bulb again, just to make sure it hasn’t burnt out...
Check fuse #24 and also check terminal R2. Both have to do with the brake lamps.
The owners manual for my 2011 also lists terminal R2 as part of the brake circuit also.
Verify with a test meter that you indeed don't have power to the 3rd brake light. I need to research it. 3rd brake lights used to used a simple diode based circuit that required both taillights to be lit in order for the 3rd brake light to power up. I'm not sure if this is the case on the Fortwo or if it triggers from terminals on the brake light switch. But in any case be sure both taillights light up when you press the brake pedal. The left and right side each have their own fuse. DCO
The taillights each have their own separate fuse. Fuse #7 is the left taillight and fuse #6 is the right one. If I remember correctly when the fuse is out the front turn signal will not blink either, but I'm certain on the rear neither the parking light nor your turn signal will light. And since the turn signal on a side doesn't light that means the brake light won't either because your brake light merely lights both turn signal bulb filaments at the same time. DCO