Howdy, so I have a '91 civic with a d15b. Its been my daily driver for around a year now, so before summer started I decided to check my freon, and it was PLENTY full. Once summer started I went and did an on site job and my car sat for about a month in the Texas heat without being ran. Flash to end of my working term, driving home my AC is awful, barely blowing coolish air. Once I got home I checked freon and it lost at least half of the freon. I recharged it and its blowing cold again. Could the heat have caused the freon to leak? I never had any leaking before.

Best regards

One more thing, I had an issue where I essentially burned off all my coolant from a bad head gasket and overheated really bad, the AC had noticeably stopped working that day I overheated. It was a long process burning the coolant but I don't know if super low coolant would affect the AC in anyway. Just thought I'd add that. Also, I replaced the head gasket so that issues fixed

 

You have a leak in the system, perhaps a bad o-ring or pinhole in the line(s). You can evacuate the existing refrigerant and then pull vacuum on the system to see if it holds. I recently fixed the issue in my wagon. Culprit were: bad AC compressor and expansion valve