I recently started up a walkin freezer box. Receiver at 50%. temp in box is fine. How come the sight glass does not clear? 2 ton condensing unit 404a refrigerant suction @ 13 psi discharge at 200 psi no head master.Unit on top of box in a 70 ambient no restictions . This seems to fool a lot of techs They always want to clear the glass without torching the receiver ending up with an over charge.