Lennox Central AC Doesn't Cool

HVAC-ers,

Lennox central air that came with the house. Both the house and system are 3-1/2 years old. I've noticed lately that the compressor has been running continuously, and the house has been warmer than usual. With the thermostat set to 70F, the system struggles to keep the house at 74 downstairs and 77* upstairs. Low 70s are attainable at night, but the heat of the day (Virginia) brings temps up during the day. Turning the system off only makes the house a few degrees warmer, so it's clearly struggling.

Yesterday I shut the system off for six hours in an attempt to melt any ice that may have formed, and I replaced all filters. I started the unit up again. I'm getting a little more airflow (the filters were kinda dirty), but it's barely cool air. Still won't cool house below 74* or so. I shut the system off.

I'm not an HVAC guy, but I used to be a professional mechanic---so I know my way around a toolbox. To me, this is screaming 'low refrigerant', but I don't understand how a 3-1/2 year old system can already be leaking. Anything I can check before calling a tech?

submitted by /u/demproteinz
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