1

my AC unit was frozen up Saturday so I went outside, and cleared all the debris (leaves, pine straw etc) from around the base of the unit, and off the top of the unit and left the unit off for about 12 hours to "thaw"

I have now cut the unit back on, and it has been running for 6 hours, no freezing up, but the set-point (of 73) is never being hit. When I use the "gun" to check the temp of the air being blown from the vents it reads at a 75, and the thermostat reads an internal temp of 78 (usually as low as it will get during the day for about the past week).

Does this sound like a low on coolant type issue or something else? Something I can repair on my own, or do I need to call out a professional to diagnoze/repair?

5

Call a service technician. Your system probably has a leak, and is low on refrigerant.

The system iced up due to low refrigerant. Then as more refrigerant escaped, the system lost the ability to cool.

1

I'm going to assume that this is a traditional split central air system, where there is an outdoor condenser and an indoor air handler or furnace. In these systems the only part that can typically freeze is the evaporator coil, which is within the air handler or furnace.

If that's right, then cleaning debris from your condenser, while a good idea, probably will not affect the freezing. Freezing would happen due to blocked drainage or limited airflow.

Have you checked your condensate drain from the air handler? It's usually a small PVC line that runs to a floor drain or outdoors. These can get clogged due to dust or mold. Inspect your evaporator coil to ensure they are not blocked. See also: How often should I run a bleach and water solution through condensate lines?.

If the condensate drain is OK, the other likely culprit is airflow. Do you have a relatively clean filter? Are your intake and supply vents and dampers open? Is the evaporator coil itself obstructed with dust or other objects?

Another possible cause of evaporator freezing, especially if you only see ice forming on one section of the coil, is refrigerant loss. If that's the case, you will need to call out a pro to repair the leak and add refrigerant as needed.

  • What I noticed iced over is the copper (I believe it is) wire that runs from the outside unit into my home. I only noticed it as the black insulation that usually surrounds the wire was completely cracked through and covered in ice. This unit is on the ground, but runs into my crawlspace up to the attic where it connects to ductwork and provides air supply to my 2nd story. Would the condensate drain be in the attic? – user2676140 Jun 12 '17 at 18:32
  • Yes, the refrigerant lines would run up to an air handler or furnace in your attic. That needs to be inspected. Condensate would run down from there (often routed next to the refrigerant lines, but can also just go out into a roof gutter). Same likely issues, though it's also possible you have something else going on, e.g. a major leak in the ductwork that is causing your air handler to take in hot attic air. – Shimon Rura Jun 12 '17 at 18:45
  • You have checked your air filter right? Restricted air flow across the condenser coils have frozen many a unit. – BD72 Jun 13 '17 at 4:11
  • @BD72 - yes, air filter was changed about 15 days ago - (I am anal retentive about changing them every 90 days) – user2676140 Jun 13 '17 at 13:12

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