Here's a *general* outline. Specific procedures and refrigerant type may vary for your vehicle, so consult your owner's manual or a repair manual specific to your 1999 GMC Jimmy. Failing to follow the correct procedure can result in injury or damage to your AC system.
What you'll need:
* Refrigerant: You'll need R-134a refrigerant (almost certainly for a 1999 model). Do not use any other refrigerant. Buy this from an auto parts store – it comes in cans with a hose and gauge.
* AC Manifold Gauge Set: This is crucial. It allows you to monitor the system's pressure and ensure you're adding the correct amount of refrigerant. The gauges will have low-side and high-side connections.
* Vacuum Pump: This is essential to evacuate the system of air and moisture *before* adding refrigerant. Moisture in the system can severely damage the compressor.
* Leak Detection Kit (optional but highly recommended): Before charging, you must check for leaks. A leak detection kit uses dye or an electronic detector to locate leaks.
* Safety Glasses and Gloves: Refrigerant can cause frostbite and eye injury.
* Wrenches: To access the low-side and high-side service ports (usually located near the compressor).
General Steps (Again, Consult your vehicle's specifications!):
1. Safety First: Wear safety glasses and gloves. Work in a well-ventilated area.
2. Locate Service Ports: Find the low-side and high-side service ports on your AC system. They're usually capped.
3. Leak Detection: Use a leak detection kit to check for leaks *before* doing anything else. Repair any leaks before proceeding.
4. Evacuation: Connect the vacuum pump to the low-side service port and evacuate the system for at least 30 minutes, preferably longer (an hour or more is better). This removes air and moisture. Monitor the vacuum gauge to ensure a good vacuum is achieved (usually below 29 inches of Hg).
5. Charging: Once the system is evacuated, connect the refrigerant can and manifold gauge set to the low-side service port. Slowly introduce refrigerant according to the pressure readings on the manifold gauge. Your owner's manual or a repair manual for your specific vehicle will have the correct pressure specifications for your system's temperature and climate. Don't just add refrigerant until it feels cold; you risk overcharging and damaging the compressor.
6. Check Pressure: After charging, turn on the AC and check the low-side and high-side pressures again. They should fall within the specified ranges for your vehicle's ambient temperature.
7. Monitor Performance: Observe the performance of your AC system. If it doesn't cool sufficiently, there might be another problem (like a compressor issue, clogged condenser, or restricted airflow) that needs professional attention.
Disclaimer: This is a simplified overview and may not be completely accurate for your specific vehicle. Improper AC service can be dangerous and result in serious damage to your vehicle's AC system. It is strongly recommended that you take your vehicle to a qualified automotive technician for AC service. They have the proper equipment, training, and experience to diagnose and repair AC problems safely and effectively. Saving a few dollars now could cost you significantly more later.
