If the air conditioner in your Nissan Xterra begins to blow out warm air, you may need to recharge the system with refrigerant. A professional mechanic will be able to recharge the air-conditioning unit in your Xterra, but this will be costly. A more cost-effective way to restore cold air in your vehicle is to recharge the system yourself by purchasing a can of R134a refrigerant, which can be purchased at auto part shops. Recharging your AC unit within your vehicle takes a few steps and can be done any time you notice the air conditioner is taking a long time to cool your Xterra.
Allow the Nissan Xterra's engine to cool down completely before working on the vehicle.
Open the bonnet of the Xterra and locate the air-conditioning unit's service fittings. The service fittings are located on the hoses coming from the condenser. The low-side fitting is located on the hose running from the accumulator to the condenser. The high-side fitting is found on the hose running from the compressor to the condenser.
Assemble the can of R134a refrigerant by attaching the service hose to the valve located on the top of the can. Twist the valve to the "on" setting. This will puncture a hole in the top of the can, allowing the coolant and air to be released. Turn the valve to the "off" setting to avoid loss of extra coolant.
Attach the R134a service hose to the low-side fitting on the air-conditioning unit. Turn the Xterra's engine on and set the air conditioner to the highest setting. Twist the valve on the can of R134a to "on." This will begin the charging process by allowing the coolant to flow into the system.
Continue charging the air conditioner until the entire can of R134a is empty. Turn off the engine and switch the valve to the "off" setting. Disconnect the can of R134a from the service fitting and close the bonnet of the Xterra.