Don't let an electrical problem leave you stranded on the side of the highway, where you might die from thirst, starvation, or an errant cell-phone-talking driver! A voltmeter gauge can give you an early warning of an alternator failure or excessive current draw from a powerful sound system.
VDO's voltmeter gauge is 2-1/16"diameter and is backlit for night time driving. Gauge measures from 8 to 16 volts.