Freon is added into the low side ac port. Using the proper type Freon, and a gauge that works with that type Freon, connect the hose to the port. With the engine running allow the Freon to flow until the gauge reads in the ok range.
In the low side ac service port.
The 1999 Oldsmobile Alero does not have Freon in the A/C system. It contains R134 and not Freon which is R12. As I am sure you do not have the proper equipment to recharge the system plus the fact it is illegal to add refrigerant to a system with a leak, until the leak is repaired, take it to a professional and have the leak repaired. You have a leak or you would not need to add refrigerant.
FreonThe connection is on or close to the receiver dryer. If you add too much, the compressor will lock up or it won't cool very good. They don't sell Freon any longer. By the way, your car takes R134A refrigerant. If you add Freon, you ruin it.
Low pressure line Larger line running from compressor
R134a
None, the refrigerant is R134a not Freon which is R12.
R-134
R134a
never use it
R134a
R134a
You don't add Freon as it has R134a not Freon. You add it to the low pressure side which is the larger hose.