Audi A6C7 2011-2014 with taillights constantly have problems due to the leakiness of the body, the restyling lights are updated and problems are much less common.
A common problem is that one LED burns out, and because of this, the electronics completely turns off the strip with all the LEDs.
If 3 LEDs are not lit at once, then the problem is most likely in the RBG BH-16 transistor.
If the entire strip is not fully lit, but all the LEDs are serviceable - then look for a problem in the power supply line or in the operational amplifier
The lantern is not disassembled, so you need to cut the body, then soldered it with a soldering iron.
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The previous problem with the taillight is described in my blog on DRIVE2 https://www.drive2.ru/l/5734239022612... / then it was enough to replace one pin in the contact chip and the rear dimension worked fine for more than a year.
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Pinning of the contact green chip 4H0873713D rear interior light:
1 pin - brown - ground
2 pin - gray yellow - turn signal
3 pin - gray black - stop signal
4 pin - white blue - overall
5 pin - black white - fog light
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Articles:
Rear left lamp VAG 4G5945093A / 4G5945093G
Rear right lamp VAG 4G5945094A
LED for stop signal CLM4B-RKW-CWaXbAA3 https://www.chipdip.ru/product/clm4b-... red 624nm 4 pin
Two-channel low-power operational amplifier LM2904DR
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My blog on DRIVE2 https://www.drive2.com/users/mark47/