Nippon Denso A/C compressor

["Michael Benno" <mbenno@mr.net>]

A/C leak found. The blue light test proved my compressor to be the source
of A/C leakage. The mechanic said that my compressor was not original. It
was a junkyard pull from and 1985 Audi 90? What the hell is this? Is that
the generic name for a 4000?.

Anyway it is bad. I have the Nippon Denso unit and I was quoted a new price
of......$650!!!!!!!!!!!!!!!!!!!!!!!!!! 

Questions?
1. Can it be rebuilt?
2. Can I get on cheaper?, where?
3. Should I get another used one?

Suggestions appreciated.

Thanks
Mike Benno
90q20v