Problem
A hissing sound comes from the AC unit while it is running.
Possible Causes
Refrigerant leak
High pressure in refrigerant lines
Air escaping from ductwork
Loose internal component
How To Fix It
Turn off the AC and listen for where the sound comes from
Inspect visible refrigerant lines
Check vents for airflow leaks
Restart the system to confirm the sound
When To Call A Professional
A hissing sound often indicates a refrigerant leak and should be inspected by an HVAC technician.
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