The issue is the low freon. Simply adding freon will not fix the problem and could actually damage the compressor further. Low freon is almost always a symptom of a leak somewhere in the system.
Here's what you should do:
1. Find and repair the leak: This is the crucial step. A qualified technician needs to locate the leak using specialized equipment (like UV dye). The leak could be in the condenser, evaporator, lines, or seals. Ignoring the leak and simply adding freon will just result in the same problem repeating, and potentially damage your compressor.
2. Evacuate the system: Once the leak is fixed, a technician needs to evacuate the system using a vacuum pump to remove any remaining air and moisture. Air and moisture in the system will severely damage the compressor and other components.
3. Recharge the system with the correct amount of refrigerant and oil: The system needs the correct type and amount of refrigerant (R-134a is likely for your 1999 DeVille) and oil. A qualified technician will know the correct amounts. They'll use gauges to ensure the system is charged to the proper pressure.
Do not attempt to do this yourself unless you have extensive experience with automotive AC systems and the proper tools. Improper handling of refrigerants can be dangerous, and attempting repairs without the proper equipment can lead to further damage and expensive repairs.
In short: There's no reset button. You need professional AC service to find and fix the leak, evacuate the system, and properly recharge it. Trying to bypass this will likely cause more problems and cost you more money in the long run.
