Well, there's a couple answers for you!
I suggest a voltmeter over a test light as you can get more use out of it. The function of each is the more or less the same though for what you want.
For a 'few buck more', get a digital voltmeter so you can actually see the numbers. It's much more beneficial to be able to see the actual amount of voltage going through something, as that can help you determine more than just simply a light giving off a bit of light.
The function of a volt meter is very simple (regardless if it's digital display or analog needle movement).
The volt meter may have a few different settings.
- If you have the option of measuring AC or DC voltage, select DC. Direct Current is what you use for checking batteries and other things in your car. Alternating Current is for checking electricity in your house and other things that get plugged into regular utility outlets.
- The next setting that you may have is to select the voltage range ("sensitivity"). Example: 1.5v, 3.3v, 9v, 12v, 110v, etc. Your car is a 12v system, so you'd select that if it's an option. If you don't have any voltage selections, it probably has an auto-sensing feature which is typical on the better, digital voltmeters.
Once you have the voltmeter set, check the location in your fuse panel. You should have two separate parts that represent bridge that the fuse links together.
Try the following test with the car off, ignition on, and engine on.
Attach one lead of the voltmeter to one side of the fuse link, and the other voltmeter lead to the other side.
Do you get a reading on your meter? If not, you have no voltage.
Note: Depending on the type of connection , you may need to use small "alligator clips" so you can more easily attach to the fuse link. If it's a blade fuse type connection, you can probably wedge your test leads in there or at least hold them in place. Don't force them in there though; you don't want to spread the clip or risk breaking the connection in the fuse panel. You only need a very little bit of connection between your test lead and the source in order to get a reading. A solid, secure connection is always better, but not 100% critical for simple testing of line voltage.
Good Luck!