For several years I have had four HD units - all on the same circuit. Within a few months, two of them went out. So I ordered two of these lamps, installed them and - nothing. So don't think the bulbs are bad. The lamps were to blame, although there were no signs of internal damage. They even had a normal "hum" when turned on. New replacement bulbs worked fine in other lights. Too bad I didn't take the time to look at them beforehand. But I'll keep the old bulbs as spares and put the new ones (they're a bit brighter when they're new) in the work lights. I then converted the faulty lights to LEDs by removing the ballasts and plugging the outlet directly into the line-in. With the new 15W/5000K LED lamps, they are just as bright as ever. So if you have another working headlight, test your "bad" bulbs in it before purchasing a replacement. In any case, a good reason to convert the lamp to LED and save even more energy. They fit the same socket as HD incandescent bulbs - just remove the ballast and plug straight in.
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