Using a multimeter to check a light socket in your home can help you pinpoint a problem and decide on the best solution. Multimeters can be purchased from any hardware store, or rented from an auto parts store for a small deposit. If you don't plan on needing a multimeter often, you should rent one. The multimeter can be used to narrow down which part of the light fixture or corded lamp is broken.
Unplug the lamp, if it is currently plugged into the wall. Set the multimeter to the resistance/continuity setting, it is the setting with the omega symbol. The omega symbol looks like an upside down horseshoe.
Take one of the leads -- which are the two cords on the multimeter, one is black and one is red -- and place it onto one of the prongs at the end of the light cord.
Take the other lead, and push it into the centre of the light socket. If there is a beep, or the meter reads 000, than that side of the circuit is complete and good. If the number displayed is higher than four, there is some form of resistance in the socket, and it is probably bad.
If the meter does not beep, doesn't show 000, or shows O.L. go to Step 3.
Remove the lead that you are holding against the prong, and press it to to the other prong on the lamp cord. If, while holding the lead against the other prong, the meter doesn't say 000, but it displays a higher number, or O.L., then that side of the circuit is bad.
If the meter displays 000 or beeps, it is a complete circuit and that circuit is good.
A corded lamp, if found to be bad, can either be replaced or repaired. The choice is up to you.
Flip the switch on, if you are testing a ceiling light or vanity lights. Set the multimeter to the voltage setting. This setting usually has a V next to it.
Remove the light bulb, if there is one. Place one lead from the multimeter into the socket, where the bottom of the light bulb would touch. Place the other lead at any point along the side of the socket, where the light bulb screws in.
Check the multimeter. The display should show a number around 120V. If the number is smaller than 110V, or the display reads 0, the wiring to the socket, or the socket itself is bad. Replacement of the socket or wiring will usually require the services of a professional electrician.