How do you know if one of your HID's are starting to go out?



If you really want to test it, you can swap left/right to see if the effect follows the bulb.
I wouldn't buy the replacement bulb from the dealer though, they'll charge you double the price of what you can get outside.
On Ebay, you can get HID bulbs as cheap as $20/each or as expensive as $200 each. All depends on what you want.



