you must flush the evaporator /condencer and all the hoses with CTC or carb cleaner spary ,,,,,,,,,,,,fill the right oil in the right quantity ,,,,,,,,,,,3-3.5 ounce per pound of gas ,,,,,,,,,,,,,,,,change of dryer is must , dont open the seals of dryer till its ready to fit , ask him to use the old dryer during pressure check the system ,