Electric Problem - Won't Charge Battery - '98 5.7

A week or so ago my battery light came on and all power to the truck was coming just from the battery. Figuring it was my alternator I bought a new one and installed it. That worked fine for a few days and now it is doing the same thing. Occasionally the light will go out and the gauge reads back up to 14 amps but only for a minute or so and then back to only the battery poering the truck. Another strange thing is when I jump on the gas and get the engine up to 3000 rpms quickly the battery light goes out but comes right back on once the tranny shifts and the rpm's drop.
Before I take the truck to the shop to search for shorts or other problems is there any common or obvious problem I am overlooking?
Thanks in advance,
Ken

My 98 Z71 did that a few weeks ago. It was the rectifier on the back of the alternator. The shop that rebuilt it for me said that it was a common problem with those alternators, he said that 90% of the time it was usually that rectifier. Changed that part and it hasnt done it since.

If that is the case, then if it has happened on two alternators now, something else sholud be causing the rectifer to go bad,...shouldn't it?

Happens to me every now and then. The positive battery cable seems to get every so slightly loose. Can't tell by hand but things light back up when I grab. I just give it annother crank and off I go.

Well,I went back to the parts store that I bought the alternator from and took it off there and had them test it. They said it was definately fried and gave me a new one free of charge. Wasn't expecting that but I'll take it! The owner of the store also has a '98 and he said his went through a couple of alternators because of bad positive cables. So for $22.00 I got a set. I installed everything right there in the parking lot and they came out and read the amps for me when I was done. They said everything seemed okay. Once I got home I took the battery out to give it a full charge and I'll go from there. Hopefully I won't have any other problems with it.