* Refrigerant Type: Older vehicles like a 1991 Suburban likely use R12 refrigerant, which is now banned due to its ozone-depleting properties. Improper handling of R12 is illegal and harmful to the environment. Even if you *could* find R12, it's incredibly expensive. Most likely, a mechanic would convert your system to use R134a, which requires more than just adding refrigerant.
* System Leaks: Simply adding refrigerant won't fix a leak. The system needs to be checked for leaks using a specialized dye or electronic leak detector, and any leaks need to be repaired before recharging. Adding refrigerant to a leaky system is a waste of money and harmful to the environment.
* Compressor, Condenser, Evaporator, etc.: There are several components that could be failing, not just the refrigerant level. A professional will diagnose the entire system to determine if other parts need repair or replacement.
* Vacuum and Proper Charging Procedure: A proper recharge involves evacuating the system to remove air and moisture, then adding the correct amount of refrigerant and oil. This is done with specialized equipment, ensuring the system operates correctly and safely.
In short: Take your 1991 Chevy Suburban to a qualified automotive air conditioning specialist. They have the tools, knowledge, and legal authorization to handle the refrigerant and properly service your AC system. Trying to do it yourself is strongly discouraged due to safety, environmental, and legal concerns.
