Sometimes it can be difficult to determine if a light bulb is good or bad, or if the problem lies in the fixture. You can see the filament of some incandescent bulbs and determine if it is broken. But with other light bulbs -- such those that are frosted or silicone-coated -- you can't see the interior to inspect the filament. Fluorescent light bulbs also are difficult to assess. However, you can test a light bulb for electrical continuity with a multimeter and determine whether the bulb still works.
Set the dial on a multimeter to resistance times 1,000 (Rx1). This setting allows you to test the continuity on any electrical device.
Touch one probe from the multimeter to the very bottom centre of the light bulb. Touch the remaining probe from the multimeter to the side of the light bulb base, along the threads. Look for the multimeter needle to sweep across the meter face to the far right if the bulb continuity is good; a digital multimeter will read zero.
Touch one probe from the multimeter to one prong on the end of a fluorescent tube. Touch the remaining probe from the multimeter to the remaining prong on the end of the tube. Look for the same sweep across the meter face or a reading of zero if the tube's continuity is good, as you did with the incandescent bulb.
- A fluorescent tube may show good continuity, but it could have a fluorescent gas leak that renders it useless.