You don't need a bulb at all to test the fixture. There should be one main "neutral", and one main "hot" wire coming out of the fixture. If there's more than one of each, you can tie each set all together, or test each one individually. The following procedure assumes a single "hot", and single "neutral".
First, set the multimeter to test continuity , or the lowest resistance setting.
Test the "neutral" wire
- Put one probe on the "neutral" wire.
- Touch the other probe to the threads inside each socket.
Next, test the "hot" wire.
- Put one probe to the "hot" wire.
- Touch the other probe to the contact at the bottom of each socket.
The threaded portion of each socket should show continuity (or low resistance), with the "neutral" wire. While the contact at the bottom of the socket, should show continuity (or low resistance) with the "hot" wire.
If one or more of the sockets doesn't test out, you may be able to repair the fixture. It's up to you if you're willing to put in the work.
If you know what size socket it is, you might want to fit a bulb in the sockets to make sure they're not physically damaged (deformed, etc.).
As @MichaelKaras points out, you'll also want to check to make sure there's not continuity between "hot" and "neutral", or either of those and the body of the fixture.
- With the multimeter set to test continuity (or low resistance). Place one probe on the "hot" wire, and the other on the "neutral" wire.
- With one probe still on the "hot" wire, touch the other probe to various metal parts on the fixture.
- Place one probe on the "neutral", then touch the other probe to various metal parts on the fixture.
If any of these tests show continuity, then the internal wiring is likely damaged.
I have a multimeter and I don't want to spend more money on other electrical test devices.
While, I understand your thought process, keep in mind that multi-meters, when combined with house wiring are not nearly as safe to operate as devices designed to perform these tests. You are paying not only for utility but also for safety (which is far more important).
circuit tester
I guess you mean outlet tester specifically.
- Set your Cat II or better rated multimeter to a high voltage AC range. If your meter has a Low-Z range intended for 120 V AC (or 230 V AC), use that.
Double check that you have the leads in the right sockets for voltage testing.
Measure the voltage
- between ground and neutral
- between ground and hot
- between hot and neutral
Check that the results match what you expect (e.g. 0, 120, 120).
GFCI outlet tester
You can't test this with just a multimeter. You need a load that will pass about 8mA at 120V (or >30mA at 230V for UK/EU readers) between hot and ground.
(Note, according to NEMA, a GFCI "test" button uses a 15kΩ resistor with a suitable voltage rating. This means the test current is nominally 8mA at 120V (or up to 9mA for a 10% tolerance resistor)
A typical multimeter has a 10MΩ impedance on its AC voltage ranges, so it passes less than 12 micro-Amps at 120V - too small to trip a GFCI. A "low-Z" range might use a 3kΩ impedance and pass 40mA at 120V - this is more than is needed for safely testing a GFCI. Note that around 10mA is the let-go threshold for humans and so currents above that can be problematic.
Fabricating something that is safe for use with 120 V AC is going be difficult to do for less than the cost of a purpose built tool.
Best Answer
To test voltage, you'll want to set the meter to the "Volts AC" setting. On the meter it will likely look like a capital "V" followed by a "~".
Typically there will be more than one setting within the range, so you'll want to choose the setting that is higher than what you expect to get. For example. In the US a lighting circuit is typically 120 volts, so you would choose the "200" setting typically found on most meters.
Check the documentation for the meter you're using, to determine where each probe should be plugged in. Typically the black probe goes in "COM", while the red goes in "VΩmA", "VΩ", or "V".
Carefully touch one probe to a known good ground, and the other to the "hot" conductor. (When I say "ground", I don't mean dirt. I'm talking about electrical ground). Next with the one probe still touching ground, touch the other probe to the "neutral" conductor. (When I say touch the conductor, I mean touch an exposed part of the conductor with the tip of the probe. Touching the probe to the insulation on the wire, isn't going to do anything). Finally, touch one probe to the "hot" conductor, and the other to the "neutral".
When you measure between ground or "neutral" and "hot", you should measure line voltage (about 120 volts). When you measure between ground and "neutral", you should measure 0 volts.