block all open lines , I use the plastic taper plugs , taped in place . ounce you complete the job , the system MUST be evacuated to remove AIR , THEN recharged . so keeping things clean IS the goal , not so much as dampness or such .... ( no you can't just add freon .. the space is allready taken up by AIR , you gotta remove the air first) I would replace the dryer any way .