I have a 82 240d and i had the a/c compressor replaced, but i never replaced the dryer and expansion valve... The AC works at first but now it blows air, is my compressor shot or how can i test that?

You had a mechanic replace the compressor.... and he replaced it without insisting the receiver dryer be replaced at the same time ?

yep.... it was not the most reputable place it was where i bought the car and they offered to install it and i didnt know any better at the time

I assume you mean it worked when they first replaced it... now it does not work... ?
Or do you mean when you first turn it on it works and then stops putting out cold air ?