Sounds like you did over charge it.Get a pressure tempature chart off the
internet.Charge it up according to that chart. At best,your system will be
acceptable. Your system was designed for r-12.It is not that 134a is not
good. It is.The higher pressures that 134a uses,makes the expansion valve
suspect,here.You need a new one that is for 134a. Unfortunately,to put it
in, requires lots of expense. Remove the vent cover,up top, and look in and
see if the expansion valve is shiny and new.If you got a new valve and it
is properly charged, go for a drive on a rainy day. The water on the
condenser will make your condenser seem larger than it really is.Liquid to
air heat transfer is much better than air to air,like is normal,here.If the
a/c cools better then, maybe consider duel condensers .If the compressor is
in good condition,and there is no moisture in the system,that is about the
best you can expect.Hope you only need a new expansion valve.