Multi-meter, not volt meter. Sorry for the confusion
I'm not sure about the security wire; It may vary by year.
A test light won't tell you anything about current, either. Current is measured in amps and the only way to measure that is with an ammeter (on the multi-meter). Though, the point is moot.
You can't check for how much current something is drawing if there's nothing connected to that circuit. In other words, that may be a 200W stereo (meaning that it would draw about 16.6 amps of
current when on), but there's no way to check for current if it won't power up in the first place. A wire not connected to a completed circuit doesn't have any current on it, only a potential voltage (the test light would draw a current, of course, but there's no way to measure the actual current other than looking at how bright the bulb is).
I get what you're saying, though. A test light is much easier to use, but a multi-meter will give you more precise data.
Either way, I still think it's a fuse
Anyway, I'm sure he will get it figured out with everyone's help. I have to go now.