HID Headlights
 

This X I bought a couple weeks ago came with HID dual beam head and fog lights. I've lost the low beam on one side, but it comes back and then goes again. I'm guessing that since the high beam still works the ballast is good, but the bulb is dying. With ballasts at $100 and bulbs around $25 I'd rather not start throwing money to diagnose it. Anyone have experience with HIDs? I'm not in town with the truck, but I'm guessing swapping the bulbs would be a sure fire way to find out.

Just got back in town and switched the bulbs. I figured the ballast and bulb would be bad and I would have no headlights. Today must be a good day since they're both working now.