Problem with Air Conditioner Freezing

May 30, 2010 by Shawn Mack  
Filed under Ask Thomas

First Name:  Gregory

Last Initial:  L

Problem: It’s a mini-split A/C.  Has worked perfectly for seven years.  This week I noticed that the brass coupling or valve cap that attaches the tubing to the outside unit is developing frost, and while the unit cools the house fine, it runs constantly; that is, the fan (which appears to run slower than it used to) never turns off.  Had it checked and the freon topped off, but the problem is still there.

Solution:  Most mini split air conditioner evaporators run constantly.   They are designed that way to continually bring in air through the indoor unit to monitor the air temperature for the thermostat.  Freezing of components in mini split air conditioners is usually contributed to a leak at the connection point or too low of refrigerant.  Make sure the proper amount of refrigerant is in the system.  Most manuals will tell you the amount needed for proper pressure settings.  Make sure to use a R22 or R410 gauge to monitor this pressure.  Pressures get low and air conditioners show freezing.