Lights flickering on stock 1G??!!

[90TurboTSi]

The lights on my 1G flicker all the time, inside the car and outside the car. The alternator in the car has less then 20k and is only a year old. I took it to the local battery shop and they did a voltage check on it, and said it was low, ans that the alternator was going bad. I had an extra alternator laying around so i put it on. (this alternator was boxed up for a long while and may have gotten banged around) The new alternator did not fix the problem, and is making weird noises. What are the chances that both are bad...or could it be something else in the system? Should I just go buy a new alternator. I figure the only way to be sure of what it is is by replacing the alternator, but is there anything else I should check? Oh, and the car is stock, no added electronics at all.
thanks
Jon

[alanseijas]

Don't just go out and buy a new alt without really testing it. The bat shop you visited should have done a load test and amperage test along with the voltage test. Did they tell you what your voltage is? If it's under 13.3, it's no good. A battery will not charge if it's that low. You could, however, have 13.3 or higher without a load on it; and as soon as you do put a load on it, POW---- low voltage.
Get it tested properly.