Xenon Control Unit Left=Right Fits AUDI A3 Sportback A4 B7 8E 2002-2013

symptom of a bad headlight ballast number one noticeable change in headlight when the ballast is failing the headlight will dim change color flicker and make a buzzing sound another symptom of a ballast problem could be if your lights suddenly stop working after some time of driving the car and then after some time when you switch the ignition and lights back on your lights start working again this happens a lot with aftermarket hid z non-light retrofits sometimes ballasts installed near a hot surface will suffer and the ballast enters in safe mode so it shuts down to avoid being damaged when the ballasts cool down they start to work fine again hid z-non-lights and ballasts depend on each other to work properly sometimes it is hard to determine whether the problem is in the ballast or in the bulb unless the bulb shows damage when you are inspecting it it's very easy to see when a xenon