AC Drain Line Clog: The $5,000 AC Problem Homeowners Don’t See Most homeowners focus on the obvious parts of their air conditioner when it starts acting up. They think about the compressor, the thermostat, or the refrigerant. But there is a silent failure point that often goes unnoticed until it causes serious damage and expensive repairs. This hidden danger is the condensate drain line . When it clogs, the consequences can be brutal: water leaks, ceiling stains, mold growth,