Sounds like it's low. If you've converted to 134a, pick up a cycle switch for 134a and install it into the receiver dryer. It will make the compressor cycle correctly for the pressures of the new refrigerant. You can readjust the R12 switch, but unless you have gauges or know how much to turn the little adjusting screw, the $15 or so for the new switch is worth it.
anyone got a Part # for the 134 "cycle switch" ?? ( if you go into a "parts store" and ask for one, you get "you want a what ? what engine ? Does it have Air Conditioning ? ", no I want a AC switch for an "Ornament" ! LOL Thanks