Performed heat check on an American Standard heat pump system. Checked electrical, mechanical, safety, and performance of the system. Electric heat strips for auxiliary heating are functional. I ran the system in heating and cooling for several minutes and both are operational. Condenser was cleaned. The condensate drain had a partial clog and had buildup along the entire length of the line. I tested the drain line and found that it was backing up. I used drain treatment to break up the clog and then cleared the drain. I then rechecked the drain with water and the drain is now flowing. Once done, I treated the drain. No other major issues were found, and system was running at the time of departure.