Went to recharge the AC today. Everything went well until ---

I got one can of refrigerant into the system, cranked the engine and found
the clutch will not engage, nor will it take any more refrigerant with
engine running or not. Refrigerant lines felt cool as the first can went in
but not since. The AC controls were set properly, but no go.  How does one
go about checking the clutch while the compressor is on the engine? I can
hear a faint clicking like something turning on and off, but not sure what
it is. The system still had some 135a in it but it got low enough to shut
itself off last year. Haven't run it since.

This is my first foray into the vanagon AC. Lots of mysteries to learn
about. Any suggestions?

John