When LED flashlights are not working correctly people are often confused because they don’t behave like old-fashioned flashlights with incandescent bulbs. The usual problem with LED flashlights is flickering or blinking which can be temporarily fixed by shaking and if the flashlight has multiple LEDs, some may not be lit or are dim. While these problems more often occur with “bargain” LED flashlights, they are not uncommon and the steps below can often fix the problem.
1. Replace the Batteries
When the batteries are low in a flashlight with an incandescent bulb, the light is dim and will eventually go dark as the batteries drain. When the batteries get low in a LED flashlight the electronics driving the LED(s) react in a variety of ways to try to compensate. Depending on the design this can often result in the characteristic flickering and/or dimming of some (but not all) of the LEDs in the case of a multiple LED flashlight.
Just replace the batteries with fresh ones and see if that fixes the problem.
2. Check and clean the contacts
While you are replacing batteries in the LED flashlight, it is a good time to check and clean the contacts. Check first that all the battery contacts touch the batteries. If the batteries fit into a carrier that then is inserted in the flashlight, check to make sure that carrier contacts are solidly touching the flashlight contacts.
Finally (and this is most important with inexpensive LED flashlights), check for discoloration (hopefully not actual corrosion) on the contacts. If there is any discoloration, gently rub with a pencil eraser until it is bright and shiny before reinserting the batteries. If there is actual corrosion, more extreme measures will be needed but the first step is to try something more abrasive to clean the contacts although access may be a problem. Also, if the batteries have been leaking you have a bigger problem than I can describe in general, but a thorough cleaning may fix the problem.
3. Don’t forget the warranty
Most name brand LED flashlights have warranties, so if your LED flashlight is still covered by the warranty, contact the manufacturer or vendor to see about a replacement. My experience with Maglite has been particularly good in this regard and they will also handle battery leakage problems because most major battery manufacturers will replace items damaged by leaking batteries and Maglite can handle the whole process for you. Other major vendors may offer similar coverage so don’t be shy about asking.