Extreme temperatures, rough roads, and lots of moisture and salt can test the design of even the best lights and bulbs, so make sure that they all work on a regular and frequent basis. Turning the headlamps and emergency flashers on when doing your morning snow brushing, for instance, makes this a no-effort job. Before tackling any bulb replacement, check for access. While the general rule is that most bulbs should be accessible without tools, some carmakers have turned this into a major process requiring body panel removal. That unforgotten tome in the glove-box, the owner’s manual, usually contains some very helpful tips on bulb replacements as well as their part number, making it easy to shop at your neighborhood auto parts store for replacements. If your ride is equipped with factory High-Intensity Discharge lights (HIDs), be prepared for some sticker shock on bulbs — those units can run from $200 to $350 and more. But before burning the credit card on one, have it checked by an experienced tech. These lamps have individual ballast resistors that can fail and darken the bulb, and a new bulb won’t fix the problem. And if you bought one and tried it, chances are good your store won’t take it back for a refund.