Your air conditioner's refrigerant lines transport refrigerant between the condenser and evaporator coils to run it through the unit for cooling down your room. But these refrigerant lines are always under pressure because of constant liquid transportation taking place. This can cause a leak to develop somewhere in the refrigerant line. When a leak develops, you will begin to hear a hissing sound because the refrigerant is now escaping through the leak and preventing your air conditioning unit from cooling down the room. In some instances, these leaks can also sound like bubbles coming out of your unit. Unless you undertake air conditioning repairs, your unit will stop cooling and will eventually break down.
The compressor of your air conditioning unit contains a valve. This valve can spring a leak, which will result in a hissing sound when your cooling unit runs. When the internal valve leaks, your AC will stop cooling the room because the refrigerant gas is no longer properly pressurised. These internal valve leaks must be fixed as quickly as possible to prevent any components from being damaged because of low pressure. If you leave this internal valve leak problem unchecked, the leak will get worse and will cause your entire air conditioning unit to break down over time.
When your air conditioning unit starts making hissing sounds, it could be because of too much pressure inside the compressor. Added pressure on the compressor may occur because of leaves, debris and dirt affecting its smooth functioning. Keep in mind that the compressor is usually located in the outdoor unit or portion of your AC. If you hear any shrieking or hissing sound coming from the compressor, you will need to turn off the AC and call an air conditioning repairs technician because this problem could cause irreparable damage to the entire unit.
If you notice any hissing sounds in your cooling unit, be sure to call an air conditioning repairs technician as soon as possible to prevent any permanent damage.