76 Scamp A/C

If you don't replace the drier and exp valve, you are being "penny wise & pound foolish". If the system has been opened for just a couple of days, the drier is shot, already. You said the system has been open for about 10 years, so the chances are excelent the exp valve will be stuck. Changing both of these parts at the getgo will be cheaper then the R-12 you waste, when you have to open the system, again.