I am trying to ass R-134a to the mechanical refrigerator/freezer system, using a 12oz can and would appreciate some advice
I hooked up with the standard gauge set, following Nigel Calder book (and as described in many other books)

I could hear the refrigerant in the can slowly boiling off. It took at least half an hour to empty the can. Is it normal to take so long (ambient about 60 F)
The system works, the freezer is good and cold, but when we run it the refrigerator takes forever to cool and the holding plate frosts MUCH more slowly than it used to.
System ahs run 8 years without any R134a top up or other maintenance.
I think the liquid refrigerant is flowing preferentially to the freezer, and little to the refrig, due to low quantity of R134a in the system. The way the piing is arranged the freezer will get all the flow of liquid refrigerant if the quantity is short.
.
Sight glass had lots of bubbles at all times when running, before adding one can. Now it has fewer bubbles and the refrigerator frosts somewhat faster.
Should I add more 134a?

Any comments and suggestions welcome.