The Nissan Xterra's air conditioning system requires an adequate supply of refrigerant to work properly. As it slowly loses its charge over time, the system becomes less efficient at cooling the air. Recharging the system with R-134a refrigerant can be done in your garage or driveway, and is a simple solution to the problem. If a recharge does not fix the air conditioning, then there is a leak somewhere that you should have repaired by a professional mechanic.
Raise the Xterra's hood and prop it open. Locate the air conditioning check port, which is on the tube running between the compressor and the evaporator. It's on the driver's side next to the firewall, and it is blocked off with a blue cap. Remove the cap.
Screw an R-134a hose onto the end of a refrigerant canister of the same type. Connect the other end of the hose to the air conditioning check port by pulling the sleeve back and pressing it onto the port, allowing the fitting to snap into place and secure the connection.
Start the engine and turn the air conditioner to its maximum setting. Check the gauge connected to the hose, which will be color-coded to indicate how high the pressure is in relation to where it should be. If the needle is in the red or yellow, refrigerant should be added.
Turn the valve on the hose slowly to the open position, paying careful attention to the gauge. Allow the needle to move until it is inside the green section of the dial, then close the valve completely. Turn off the engine and remove the hose from the Xterra's check port. Do not remove the hose from the canister unless it is completely empty. It can still be used at a later time.
