Q: How to remove and install the evaporator and expansion valve in a Nissan Sentra's air conditioning system?A: Have the refrigerant discharged at a dealer service department or an automotive air conditioning repair facility. Remove the instrument lower cover on the passenger's side. On 2011 and earlier models, remove the expansion valve. Remove the glove box. Remove the evaporator cover screws and remove cover. Remove the evaporator from the vehicle. On 2012 models, the expansion valve can be removed after the evaporator is removed. Installation is the reverse of removal. Tighten the expansion valve bolts to the torque. Note: Do not use old O-rings for the refrigerant lines, replace with new ones and apply compressor oil to them before installation. Have the system evacuated, charged and leak tested by the shop that discharged it.