ac problem?

I have a 1996 Buick Regal,3.1 engine when i turn on the ac or heater it makes a awful noise.I replaced the ac compressor about 2 years ago it only had a 90 day warr.Is it the same problem again? and i just replaced my radiator (leaking) now i noticed the fan to the radiator is not coming on.How do i check that.The fan hasn't come on since the radiator guy put it in.