Bulkhead connector

A voltmeter is a good idea, even if one keeps the dash ammeter. I use a cigarette lighter type in all my cars on long trips ($15 Amazon). They don't put anything to monitor charging in my newer Chryslers and I was surprised on a road trip when the alternator was slipping (cracked p.s. pulley) in my 2002 van. The trans indicator showed all gears, chimes were going off, the windshield wipers started actuating. New cars don't like low voltage. You should see ~14.3 V while driving and ~12.6 V when off.