Mine was charging but my headlights looked like strobe lights. The rectifier was going bad in mine.
When I started mine up Thur morning all was fine for a minute and then the truck stumbled. I thought...wtf! Then the battery warning light would flash in the message center and when I looked at the voltage it was on the first slash at where a 1/4 tank of gas would be. After it ran for about 10 minutes and I floored it it kicked in and started charging. The same thing Fri, Sat and this morning, but this morning it wouldn't even start to charge.
The original one in the Tahoe shit the bed 2 winters ago while we were still up north, it did the same thing. I found a new Delco 145 amp at the parts store from an HD, it was clocked differently, but it worked great. With it at an idle defrost on high, rear heat on high, heated seats on, and 2 amps booming, it doesn't even dim the headlights.