How to Troubleshoot Problems With Incandescent Light Bulbs

Incandescent light bulb with standard light bulbs

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In this day of compact fluorescent lights (CFLs) and light-emitting diode (LED) bulbs, the good old-fashioned incandescent bulb is getting a bit rarer, but it is still the most popular light bulb overall, and it has many merits. Its light has a warm temperature that many people find more pleasant than either CFL or LED bulbs. And the low cost is still appealing—although the cost advantage lessens somewhat when you calculate the shorter life of incandescent bulbs.

When Light Bulbs Burn out Too Soon

Incandescent light bulbs typically have a lifespan of around 900 hours—a lifespan that translates to about five hours per day for six months before the bulb burns out. However, if the bulbs are not reaching their full potential in lifespan, here are some possible problems that can be corrected:

  • One problem may be a loose contact connection between the bulb and the light fixture socket. At the bottom of the socket, there is a small metal tab that sometimes gets compressed or flattened over time. The contact tab itself may have a loose crimp, or the solder joint on the tip of the bulb may be too small to make a good connection with the post, causing an increase in resistance and heat buildup. This, in turn, overheats the bulb and shortens its lifespan.
  • Another common problem is an oversized bulb in a lamp socket rated for a smaller wattage. The maximum wattage is posted on the side of the socket and is not to be exceeded. Check your bulbs, and never install a bulb with a higher wattage rating than the socket rating. 
  • Vibrations in and around the lamp socket can also shorten bulb life. An unbalanced ceiling fan is usually the culprit here. The vibration shakes the filament and lessens the lifespan.

Commercial-grade and industrial-grade bulbs are built for more rugged use and generally last longer than the cheaper standard-grade bulbs. Rough-service bulbs are commonly used at construction sites due to their durability. They have a plastic coating on the surface of the glass that will prevent the glass from shattering. When these bulbs break, they resemble a cracked eggshell. Another nice feature of these bulbs is that they are built to withstand vibration.

If a Light Bulb Just Won't Light

When a light bulb fails to illuminate at all, here are some likely causes of the problem:

  • The bulb might be burned out.
  • The lamp or fixture wiring might be faulty.
  • The cord to the lamp could be unplugged, or the power to the light could be shut off at the circuit breaker.
  • The bulb may loosen in the socket—check to make sure it is tight. 
  • The outlet receptacle the lamp is plugged into may be bad.
  • The switch feeding the light may be defective.

If the Light Bulb Frequently Trips the Circuit Breaker

If a circuit breaker trips or a fuse blows out each time a light bulb is screwed into a light fixture, one of several bigger problems may be to blame: 

  • You may have a defective plug inside the lamp cord.
  • The light socket may be defective.
  • There may be a short circuit in the cord or wiring feeding the light.

If a Light Bulb Works but Flickers

If the light bulb flickers when the lamp or light fixture is turned on, here as some possible problems: 

  • The bulb may be loose. You'll generally see this in ceiling fans where vibration loosens the bulb, causing it to make intermittent contact and flicker as a result. 
  • Wiring connections may not be tight. A loose connection to the socket connection or the wiring to the light or fan/light combination can cause this problem.
  • Bad contacts in the switch feeding the light can be the culprit. You'll normally hear a buzzing or sizzling sound around the switch when this occurs.
  • A worn-out receptacle can cause problems when a lamp is plugged into it. The metal contacts inside the slots of old receptacles lose their grip, preventing them from securely holding the prongs on a lamp cord. Just the vibration of walking through the room can jiggle the connection and cause the light to flicker.

Problems with incandescent light bulbs can be easily solved in some cases, and can also hint at other wiring problems with light fixture sockets, wall switches, or outlet receptacles.