The lamp socket conducts electricity directed at the bulb. The lamp socket can fail and if the light no longer turns on you can test the lamp socket to see if it faulty. The following article will show you how to do this test.
Step 1 - Safety
When working around electricity you should always protect yourself. If you're going to be accessing the lamp socket or moving wires then make sure it's unplugged or the power is off at the junction box. If you're working a lamp socket in the ceiling the same safety measures apply. You may get a mild shock but there's a possibility that a stroke, heart attack or death may occur from direct contact with electricity. If you plan to work with the wires then make use of a voltage tester to ensure that the power is completely shut off.
Step 2 - Test for Basic Current
This is the easiest way to test if the lamp socket is bad or if the problem is somewhere else in the lamp. Remove the lamp shade and light bulb from the lamp. Make sure the lamp is plugged in or that the power is still on. Turn on the voltage tester and press the probe inside the lamp socket to tough the lead in the bottom. If the voltage tester lights up or beeps then there is current. This indicates a good socket which means either the plug or the bulb is defective. If it does not light up then the problem may still be the lamp socket.
Step 3 - Access the Lamp Socket
If the lamp socket is installed in a ceiling or wall then remove the light bulb and lamp shade. On the base of the lamp socket will be at least two screws. Remove them and place them aside. The lamp socket will be able to be removed by pulling it downward (for a ceiling) or out (if in a wall). The wires will not be exposed. If working on a floor lamp remove the shade, light bulb and the harp (the shade is placed over this). Depress the outer shell of the lamp socket and pull it free then remove the insulation.
Step 3 - Test for Wire Current
Now that you tested for current in the socket you can now test the wires connected to the socket. For this you test you will want the electricity turned off. Verify that it is off by using the voltage tester on the wires. For this test you will be using the continuity tester which will test for current from wire to wire and terminating points. Start by touching the tester to the screw that is holding the black wire (hot wire) and the other probe to the ground (can be bare copper, plain screw, metal box or a wire that is either brown, green or yellow). Repeat with each connecting wire. If no power is registered from any of the contacts the lamp socket is bad.