My last through-window air conditioner started smelling moldy after a year or two. Improper drainage, I guess? The instructions always say to install the air conditioner at a "slight tilt" so the water that collects will drain out the back.
But how much tilt is the right amount? My last air conditioner was tilted 2 degrees, according to a clinometer app for my phone, and it still got moldy. Should it have been 4? 5? 6?