Couldn't find cond in backyard but followed fan noise and voila!
Check out AHU, H/O couldn't find where to insert filter, not even door filter holder avail. No primary drain going out to reg drain but draining into "emergency pan" then into drain. Cutout for air intake blocks half of area and made of particle board no less.
Unit sitting in its own slime. This is an install from the oldest and largest contractors in area. Go figure!