Alternator Issue??

Hey Guys-
Well on the way home tonite from work I noticed my voltage dropping and coming back up again real quick and pretty much the enitre 20mile drive...all the lights in the truck were pulsing to the volt gauge and a few times it dropped pretty low..I've checked all the normal connections such as grounds, battery posts..etc. and the battery seems to have a normal charge.so I'm leaning to maybe being an alternator issue just wanted to make sure this is what it is before I go out and buy one tomorrow..the alternator is whining and has been for a few months but nothing loud just a little whine under the hood..it is still orginal AC Delco and the truck has about 92,000miles so maybe its due.
The truck is a 03 1500HD 6.0L w/ 105amp alt.
Thanks so much for your guys help..love this place-
Danny

I would check both ends of both battery cables. Make sure connections are clean and secure.

Recently, I had problems on my Yukon and the positive connection was pretty rusty at the battery.

//2000CAYukon

Take it to autozone and let them check your alt and battery for free.

Decided to take it over to Autozone like Blenderwizard recommended...about 15miles from my place...and on the way there the volt gauge dipped to around 12 and "Battery Not Charging" Came On the DIC but it still seemed to make it to Autozone ok..the alternator tested out completly dead by that point so I got that swapped out and also changed out that AC delco battery just for good measure and she seems to be her old self again...thanks again for the comments..great help as always
Danny-

G and R has 145A's (new) for $87 shipped.