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Suction and liquid line temps meaning for mini split in heat mode

Just curious if these temps can be used to help diagnosis reduced heat output on mini split:
Outdoor suction line temp: 115 degrees F
Outdoor liquid line temp: 78 degrees
Indoor unit heat output temp 85 degrees
(Outdoor air temp 38 degrees, indoor temp stuck around 68 with thermostat set to 72.)
I didn't use a high tech temp gauge, just my digital sensor so actual temps probably different, but is it possible that these spreads could indicate a low or high charge of refrigerant? (Assuming next step would be actual psi gauge test.) Thanks.


  • Ironman
    Ironman Member Posts: 7,352
    The only way to assure the charge is right in a mini split is to weigh in the correct amount.

    There are methods of “ballpark” checking, but not by comparing liquid and vapor temps.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • pecmsg
    pecmsg Member Posts: 4,697
    Both lines are suction on minis