voltmeter check?

[knightowl73]

ive gotten all the other guages working now (big relief) except the voltmeter. i dont really know how to use the "voltmeter" tool, but how can i check out this problem? i know of the brown wire from the alternator, and im sure the alternator works fine because the battery is keeping up a charge just fine. can i try and find the brown wire at the firewall and tap a test light into it while the truck is running or will this burn up something?