I just changed my alternator and I'm still having charging problem can anyone give me any information on the issue

 

My recent not charging issue was a bad battery. Went and had the auto parts store test the alternator and battery while they were still installed in the truck. Both tested good, I'm like no that's not right. I keep having a dead battery. Even though my side mount battery posts looked clean I figured go ahead and remove them for ha ha's. To my amazement a fair amount of corrosive dust fell out of the positive terminals connector (small gap behind it where it touched the battery) . I'm like aha, cleaned everything put it all back together and still no charging. I could easily jump start the truck, but the battery was not charging enough to get more than a couple starts. Went to COSTCO and for $93 got a new battery and it has been good since. Before the battery swap my alternator charging needle would read 12 volts, like not charging. Since the battery swap now the needle is reading at about 14 volts. So apparently the old battery was not taking a charge even though it tested good. The auto parts store wanted almost $145 for a battery with tax.

So are your terminals really clean and how old is your battery? Mine was a Nov. 2014 so almost 4.5 years old.