I would add a little more freon before changing anything.....
It does not take but a couple of 0z to make a big difference in evap/cond temp differential...
That will givwe you a start point , anyway

Ok, try this on for size. If after more than one conversion there maybe too much oil in the system.. This oil will gather in the evaporator. Think of it this way if the evaporator is 1/3 full of oil all of your pressures will look fine but you will get diminished cooling because only 2/3 of the evaporator will be cold. It's just like having a small evaporator. If the system has been converted then the oil that was installed with the hodge podge mixture is not flowing with your r12 and is just sitting there. I noticed u flushed the system but that wont bring out that old oil. I have had to go so far as to pull the evaporator and literally turn it on its side to get excess oil out of the system.

Bill

I just noticed that this was from 2003.. oh well hope its fixed