Demand call/heat preventative maintenance on two gas systems from 2011 using air filter 20*25*1 which customer did provide today to change. Demand call was for the upstairs system not cooling and having water drip out the emergency line over the garage. Upon a visual inspection the system had an “E312” error code indicating that there was lack of airflow. I checked the air filter and found it to be caked and not allowing proper airflow through the machine causing it to start building frost which led to an excessive amount of water going into the drain pan which drains outside. I took the air filter out and the machine sounded like a drowning victim, the error code cleared after a few seconds. I put the system in ac mode and let it run for 15-20 minutes, the system didnt produce an excessive amount of water because it wasn’t freezing up and I was getting 53 degrees coming out of the vents. On the maintenance I checked electrical connections and components, cleaned safety sensors, i
