Lights will sometimes dim for a few seconds and then come back to complete brightness again. This can happen when a light is connected to the same wires that provide power to something that takes a lot of power, like a refrigerator, a microwave oven, or an air conditioner.

Humming lights can be caused by:

• A bad ballast or bad transformer. Replace the ballast or transformer.
• A conflict between the low voltage dimmer and the low voltage light fixture it controls. This is a tough one, but sometimes experimenting with several dimmers will eventually lead you to one that does not make the low voltage light transformer hum.

Here are the three reasons this can happen:

• The wattage of the bulb is too high. This is very common. Most light fixtures with glass covers have a maximum rating of 60 watts per bulb. It is very common for people to put in 75-watt or even 100-watt bulbs into these fixtures. The result is bulbs burning out much too quickly. Use the correct wattage bulbs in all your light fixtures.
• Poor-quality lights bulbs. Use only major-brand light bulbs.
• Mysterious light fixture problem. It's mysterious because the light fixture looks perfectly fine, and even electricians can't find anything wrong with it. Nevertheless, after checking #1 and #2 above, if the bulbs keep burning out ... Replace the light fixture.

There are three reasons fluorescent lights sometimes flicker:

• For a few moments when they first turn on, the bulbs will flicker until they warm up. You will notice this more on colder days. Just wait a few moments for the bulbs to warm up.
• The fluorescent bulbs are old. Replace them.
• The fluorescent ballast is old. Replace it.

There are two main reasons for lights blinking on and off:

• A photo cell-is out of adjustment. Adjust photocell.
• Some light fixtures that are recessed into the ceiling have a built-in thermal protector that automatically shuts off the light when the light fixture gets too hot. Use a lower wattage bulb for a lower temperature.

Here are reasons lights don't turn off:

• The switch to the light fixture is broken. Replace the switch.
• The time clock for the light is broken or out of adjustment. Set the time clock to the right time. If it won't stay adjusted, replace it.
• If the light fixture is activated by a photocell, the photocell is either out of adjustment or broken. Adjust or replace photocell.

Lights don't turn on for six basic reasons:

• The bulb is bad. This is more common than one might think. Try replacing a questionable light bulb with a new one. If that doesn't work, before giving up, try using a bulb from another light fixture that you KNOW is working.
• The switch to the light is bad. The switch will need to be replaced.
• The light fixture is broken. Usually it is easier and less expensive to simply replace the light fixture. However, many light fixtures can be repaired if this is what the owner desires.
• No power. Please go to the No Power section.
• Time clock for the light is broken or not set for the correct time. Re-set the time on the clock or replace the broken time clock.
• If the light fixture is activated by a photocell, the photocell is either out of adjustment or broken. Adjust or replace photocell.
• Fluorescent, Mercury-Vapor, or High-Pressure-Sodium Lights. These kinds of light fixtures all use an electrical ballast to energize their special light bulbs. If the light is humming loudly, has an "electrical odor" or if the light just doesn't turn on, the ballast may need to be replaced.