What are the symptoms of insufficient refrigerant in a car's air conditioning system?

[DiAdrian]

When the car's air conditioning system is low on refrigerant, the following symptoms may occur: During normal continuous operation of the air conditioning, if bubbles persistently appear in the sight glass, it indicates insufficient refrigerant and the need for a recharge. Open the car's hood and check the air conditioning system connections for oil stains. If present, this typically indicates a refrigerant shortage. It's recommended to clean the area before recharging. When the air conditioning is turned on, if bubbles appear in the sight glass every 1-2 seconds continuously; if there are oil stains at pipe connection points; or if there's no noticeable temperature difference between the high and low pressure sides when touched by hand - these all indicate minor refrigerant leakage in the system that requires replenishment. Users who have operated the system for more than six months should check both the indoor unit's pipe connections and outdoor unit's valves for obvious signs of oil leakage. Visible oil leakage indicates system leakage, as oil and refrigerant are mutually soluble - oil leakage means refrigerant leakage, and vice versa.