Rectifier / regulator changes the AC into DC on a 12V board. This prevents bulbs from burning through. Exposure to high temperatures means bulbs often fail. If the rectifier is faulty, the ignition system can falter, the bulbs burn through, and the headlight flickers.
OEM-numbers for reference only: 641709 / 641533 / 58208R
OEM-numbers for reference only: 641709 / 641533 / 58208R