The orifice tube is installed in the condenser to evaporator line in that has the main function of converting the high pressure liquid refrigerant to low pressure liquid. First, have the air conditioning system discharged by a dealer service department, or an automotive air conditioning shop if possible. Next you get rid of the refrigerant line containing the orifice tube by unscrewing the high pressure A/C line and using needle-nose pliers to remove it by pulling with an open-end wrench, on the stationery connection and a flare nut wrench to avoid rolling the tube nut. Withdraw the orifice tube with the help of needle-nose pliers while making sure that the tapered mesh screen in the opening of the orifice tube is not damaged; if it is damaged or stuck or if some of it breaks off, then you can from a set of extractor tools in most auto parts stores. Installation is the reverse of this procedure, it is important that the used O-rings are removed and discarded and new O-rings are inserted. Last of all, drive the vehicle back to the workshop that has charged it to get the system emptied and recharged, and the standard leakage check.