2006 Tahoe, 200k miles. I'm a little over halfway thru a a long road trip - Alaska to Michigan, about 4500 miles. I look at the voltmeter and most of the time it's a needle width above the "14" - this is the normal reading. Several times a day i'll notice the meter is indicating about 2 needle widths below the "14", then after an hour or so it's back up to normal. No difference in electrical load that i can determine. Is this normal operation? Is my alternator trying to tell me something? Will it go another 2000 miles to my destination?