A volt meter won't help if your checking the alternator voltage. Voltage has nothing to do with a fuse blowing, to many amps are what causes a fuse to blow. So what you would need to check alt output is an amp meter that's rated over 80 amps. The only problem is the factory alt(for older year trucks) is only rated at 40 amps and I highly doubt that it would spike over 80 amps. Most of the time a fuse blows is from something shorted to ground. Check the wirring from the fuse and follow the wire to see if rubbing, pinched or any bare wire that could be grounding out. If all the wirring is ok, check the componets that the wire goes to, unplug one at a time untill the fuse stops blowing, then you will know what is causing the fuse to blow. If this doesn't help let me know some more info, like year, model, and engine and I will see if I have a wirring diagram.
