If the air coming from your air conditioner is warm instead of cool, recharging the system may help. In models made after 1995, you may be able to simply add R134 refrigerant. Models made before this must be retrofitted to accept R134 refrigerant instead of R12.
Inspect the lines for signs of extreme wear or damage. There are some leak detection kits available at most auto parts stores that will help you to see leaks and possibly seal small leaks. If you notice any damage or leaks, you need to fix them before you try to recharge the system.
Find the Low Pressure Side port of the air conditioner. On most Jeep Grand Cherokee SUVs, this will be located near the front grill on the driver side of the engine. In some cases, you may find it near the firewall. This depends on the engine size and year model. The cap on the LPS port is blue or yellow and marked L. Remove this cap.
Look at the connector valve to determine if the system is R134 or R12 compatible in models made in or before 1995. If the valve is a quick connect valve, the system is R134 compatible and you may proceed safely with the recharge. If you see screw type connector, the system is R12 compatible and you must retrofit it before you can add R134 refrigerant.
Turn on the engine and the air conditioner. You need to put it on the coldest setting and highest fan speed. This will make all of the system components work which will circulate the refrigerant and allow you to get accurate pressure readings.
Check the pressure on the Low Pressure Side. To do this, get an automotive pressure gauge from the auto parts store. Read and follow the manufacturer's directions. These may vary slightly for each brand or type of gauge.
Connect the can of R134 to the LPS according to the kit directions. There are a few different types of kits, including quick charge, direct charge and trigger charge. Allow the system to suction the refrigerant out of the can. In some cases, this can take as long as 10 minutes. You may need to add more than one can of refrigerant to fully recharge the system.
Disconnect the refill kit according to the instructions. Keep in mind that you should leave the SUV running with the air conditioner on for at least half an hour to allow the refrigerant to fully circulate through the whole system.
