Written by Tony Carrick | Published 2:53 PM, July 22, 2021

There are a variety of reasons that can prevent a flashlight from working, from obvious battery drain to less obvious connection corrosion. The flashlight consists of a series of metal contacts that form a circuit between the battery and the light bulb. If the contacts or battery fail, even the best flashlight will not work.

Fortunately, most problems that cause flashlight failures are usually easy to solve without any special tools. The following are the most common problems that cause flashlights to malfunction and how to fix them.

Although this seems obvious, usually the culprit is the battery. In most cases, it is easy to identify a battery that is about to run out. As the batteries discharge, they release less and less power, causing most flashlights to change from bright to dark before they are completely extinguished.

If the flashlight is left unused for a long time, the battery inside may discharge slowly. Although this usually takes a long time to happen, storing a flashlight with a battery in a high temperature environment will shorten the battery life. Rechargeable flashlights (and flashlights that use rechargeable batteries) lose power more quickly when they are not in use.

You may also have a flashlight that uses a regulated output, which allows the battery to provide a steady flow of light instead of slow decay. When these batteries are finally abandoned, the light will not fade away. Instead, the light suddenly cut off.

The flashlight switch has two metal contact strips. When you push the switch to the on position, the light bar touches the light and the battery, completing the circuit and lighting the bulb.

Sometimes these contacts will corrode due to exposure to moisture, preventing one or two contact strips from making a clean connection. When this happens, the current will not pass through the corroded metal to complete the circuit. These contacts may also be bent or damaged, preventing the contacts from contacting the battery spring or light.

If you can access the contact strips under the switch, clean them with a little vinegar and check to make sure they are not damaged or bent.

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In addition to the two metal strips in the switch, there are brass or copper contacts that contact the battery. These contacts are usually composed of springs and flat metal sheets, both of which can be accessed through the battery box. The spring contacts the negative end, generating tension that pushes the positive end toward the flat piece. This creates a connection, completes the circuit in the flashlight, and lights up the light.

Since the spring is usually made of thin metal, it may bend so that it no longer comes into contact with the battery, or it may not generate enough tension to push the opposing flat metal sheet. When this happens, the connection is disconnected and the flashlight stops lighting. Open the battery box and check these parts. If it seems that the spring is not working, pull it out a few millimeters to increase the tension of the spring.

Like the contacts in a switch, battery contacts can also corrode due to moisture or even acid from battery leakage. If corrosion affects these parts, clean the battery with a small amount of isopropyl alcohol.

It should be clear by now that whether the flashlight works depends to a large extent on the metal contacts that form the circuit inside the flashlight. If any of these contacts fails to work properly, the circuit will not be completed and the flashlight will not light up.

If dirt enters the flashlight, it will work between the battery and its contacts or the flashlight switch and its contacts, thereby destroying the circuit. To clean, turn on the flashlight and remove the battery. Use a cotton swab to clean all visible dirt in the battery compartment. If the contacts become dirty, wipe them clean with a cotton swab dipped in rubbing alcohol.

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O-rings are rubber gaskets that are installed around the opening parts of the flashlight, such as battery boxes and lights. When the compartment is closed and the flashlight is in use, these rubber rings prevent water and dirt from entering the flashlight. They are especially important for the use of durable flashlights, such as tactical flashlights or camping flashlights.

If you find dirt or moisture inside the flashlight, it means that the O-ring is not working. Over time, these rubber O-rings can wear out, dry out, and crack, making them unable to perform their duties. Check the O-ring on the flashlight. If they are damaged, replace the O-rings with new ones. If the O-ring looks intact, but it looks a bit dry, apply a little silicone lubricant to it.

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