There are many reasons why lights dim. The first reason could be that the lights are on a circuit with a larger appliance such as a refrigerator or air conditioner. When the appliance kicks in, the lights may dim because the appliance took a lot of power to start. You should have a dedicated circuit breaker for such appliances that require more power to start. If your wiring is not equipped to handle the load of electricity your home needs it could result in dimming lights. This is because the existing wiring has a large current need and the voltage can drop if the wiring has too much resistance.
If the lights get brighter and dimmer, you might have a corroded, broken or loose neutral wire. If this happens, you could be pushing 240 into the 120 outlets for a second. This is a more serious problem and should be corrected immediately by an experienced electrician. If your lights dim or flicker, you need to check for frayed wiring or loose connections. Another reason that lights dim is if there is something wired on the same circuit that is faulty. For instance, if your lights dim when you start the vacuum cleaner, it may be drawing too much power because of a faulty or wearing motor.
If you notice your lights are dimming, you need to find the source of the problem. It could be the light bulb itself or it could be something more serious. Inspect wiring and observe appliances while turning on and running. If you have not found the problem yourself you should have an electrician or an electrical contractor come and inspect the wiring and appliances. Electricians do have more ways of searching for electrical problems. An electrician will troubleshoot the wiring and circuitry before suggesting what the problem is as well as what has to be done to correct it.
