turbowhine

I'm trying to diagnose my air conditioning unit before getting raped by a shop. I can easily turn the center of the compressor with one finger, and I've worked on many different non-automotive A/C units and usually this would indicate a worn compressor. Is this also the case with these car compressors? I'm thinking there should be some resistance. If your A/C work well, can you turn the compressor by hand. Thanks in advance.