Periodically test a flashlight; contact points become dirty and batteries discharge slowly, even when not in use. If practical, store batteries in the refrigerator to prolong their life.
If the beam is dim, rub the battery terminals lightly with sandpaper or emery cloth. Also sand the contact point of the bulb and the contact spring. To reach the spring, remove the cap, reflector, bulb, and batteries; insert a pencil or dowel wrapped with sandpaper. Also stretch the spring slightly with a screwdriver.
If the light blinks, sand and stretch the spring as above. Also check that the switch contact bar touches the reflector collar. If not, bend it slightly and sand it.
If the light doesn’t work, check whether the batteries are inserted correctly. If they are and it still doesn’t work, replace the batteries, the bulb, or both. To replace a bulb, remove the reflector; unsnap or unscrew the bulb protector, and insert a new bulb. If these measures fail, try cleaning all contact points.