I hope someone can help!

I have been doing a lot of research on this forum looking for the answer to this problem. It isn't anything dier, but I love my car, and I just want everything to be working right. If anyone has any ideas, please let me know!
Heres the problem... Im not sure if you have ever heard of this problem, but I have a 1998 Monte Carlo z34 with the 3800. The other day I got into my car to head home, I was driving during the day and all of my lights worked in the car, but as soon as it started to get dark out my all of my dash lights went out, I mean everything, cd player, shifter rail, speedo, ac, everything. I checked all of the fuses and they all seem to be fine. I know that none of the bulbs are blown becuase when just my running lights are on, everything seems to still work. However, when I turn my lights on for night, everything that should go dim, or turn on shut off instead. I really hope that I can find a person that has ran into this problem before or that knows the answer. Hope you can help and thanks for listening! Adam

Sounds like you have a problem with the reostat that dims the lights. Check and see if you can turn your doom light on with your doors closed. If not that is your problem.

sounds like your alternator took a crap.

Thanks guys for your help. Well, I know that it is not the alternator, just the other day i checked it and its putting out 14.8 volts at the alternator, and about 14.4 volts at the battery. I also have a brand new battery as well. As for the reostat thing, with the doors closed i can turn on the dome light and vanity lights. It weird because basically what the car is doing is instead of dimming the lights, it is just shuting them all off? Any other ideas? Thanks for the help, Eyeshyed