if yo dont have a vacuum pump to pull a vacuum.. all i did when the high pressure valve blew(had to replace it).. was to charge from the low side and let the R-134A out the high side.. the freon blew out any moisture in there...I have a home made vacuum pump from an old refrigerator compressor that i used to use in the old R-12 systems.. but the valve on it will not work with the new R-134A hoses...if you have an old pump i found out that you can get a retrofit R-134A valve to put over the old R-12 valve and the old pump will work fine....
hope this helps.
