Problem was a knocking in the drain line after the AC shut off. Juan showed up and diagnosed it within five minutes as being air in the drain line that is shared with the condo unit neighbor downstairs. Found out another company had installed a new unit downstairs and failed to put a trap in the drain line. Juan added a trap in neighbors drain line. Problem solved. Yet another reason why we have done business exclusively with Brisk and their predecessor for 25+ years.
