Paul the clutch will not pull in since there is a pressure switch wired in
series with the comp. If the freon level drops too low the switch cuts out
the compressor thereby alieviating damage to the compressor pistons.Check
with the ftp files re: changeover parts necessary for the 134a
conversion.There is also a new drop in r12 replacement out there which might
be  a cheaper alternative to 134a.
Ed Berroth
84 Westy Wolf
87 Stinkcrow