Disconnecting the battery is not optional
Countless auto repair procedures begin with “disconnect vehicle battery,” but for HIDs, that safety precaution is not optional. Here’s why.
HIDs get their powerful white glow from an arc between two electrodes. Look inside the bulb, and you’ll see that HID doesn’t use a filament like a traditional halogen lamp. Instead, the arc is contained within the bulb’s glass, along with a gas. It can take a lot of juice to create the arc between those electrodes… to the tune of around 25,000 volts to start the arc! Disconnecting the battery helps to keep you safe while working inside the headlight assembly. Compared to the bulb startup voltage, the current should be fairly tame, but you still don’t want to be on the receiving end of that zap. Pay close attention to the connection between the ballast and the bulb, and if the shielding or cable is damaged, steer clear until you’ve resolved the problem.
Also, be sure that the headlight switch is off while working on the headlight assembly. The maximum voltage is delivered to the HID bulb at startup, and an accidental connection could trigger the ballast’s highest output. Although this step is redundant after disconnecting the battery, it’s best to make sure the HID system is switched off before digging in.