sitting at an idle parked if I roll up windows or anything like that the head lights and dash lights dim. also lately I get some alternator hiss in some not all of my fm radio stations. no noise coming from alternator and is charging fine. do you think it is time for a new alternator and battery or are there other thing to consider

go get the altenator and battery tested. It wouldnt hurt but at least you will know what the deal is before you spend money on an issue and the altenator and battery is fine.

SOunds to me like a weak battery. Gotta second the "get 'em tested" vote....