Are you speaking about the voltmeter mounted in the instrument cluster or an external one you might troubleshoot with. The cluster mounted gauge measures system voltage and unless input is changed doesn't measure coil voltage.
As far as a trouble indicator goes, it might help you see something like ballast resistor failure, condenser failure or something of that order. Truth is, the engine will let you know a problem is occurring around the same time. If the LED display turns your crank, then go for it.
