2002 Audi A4 Air conditioner suddenly blowing hot air

We left the car sitting for a week at home while on vacation, and today the a/c suddenly quit working. It blows hot air, but it's also 110 degrees outside; who knows if it is just regular air blowing which wouldn't be hot if not affected by outdoor temps. The rpm's are not changing when the a/c is turned on, so I thought it could be a compressor issue, though somewhere else I read it could be a fuse. Any other ideas or ways to fix it without spending a ridiculous amount of $$ at the dealer?