Here's the breakdown:
* Don't just add freon. Adding refrigerant without knowing the cause of the low refrigerant can severely damage the compressor and other AC components. A leak needs to be found and fixed *before* adding any refrigerant. Adding refrigerant to a system with a leak will only hasten the damage.
* Checking for low refrigerant: To check if your system is low, you'll need to:
1. Turn on the AC system: Set the climate control to full cold and the fan to high. The compressor clutch should engage – you'll hear a slight "click" and might feel a slight vibration. If the clutch *doesn't* engage, there could be several reasons, including a low refrigerant charge, a faulty compressor clutch, a bad pressure switch, or a problem with the AC cycling switch.
2. Check the low-side pressure: You need an AC gauge set to measure the pressure. This requires connecting the gauges to the low-side service port (usually a schrader valve) on the AC system. The low-side pressure reading will indicate whether the system is low on refrigerant. You need a pressure chart specific to your 1990 Buick Riviera to interpret the reading accurately. Improper pressure can damage the system.
* Finding and fixing leaks: If low pressure is confirmed, a leak detection needs to be performed using specialized UV dye and a UV light. Locating and repairing the leak is crucial before adding refrigerant.
* Adding refrigerant (only after leak repair): Once the leak is fixed, a qualified technician will use a vacuum pump to evacuate the system of air and moisture. Then, they'll add the correct amount of refrigerant and oil using the pressure readings from the gauge set and the aforementioned pressure charts. This process requires specialized tools and safety precautions.
In short: Trying to add freon simply by turning on the AC is not only ineffective but dangerous. Take your 1990 Buick Riviera to a qualified automotive AC technician. They have the tools, knowledge, and experience to properly diagnose and repair your system. Improper handling of refrigerant can lead to serious injury.
