1. A method of cleaning a heat exchanger of an HVAC system, the heat exchanger having a coil matrix having a plurality of fins and a plurality of rows of heat exchanging coils supported by the fins, the coils spaced apart to define channels extending through the plurality of rows between an inlet side and an outlet side of the coil matrix, said method comprising the steps of: 1) a pre clean measuring step including taking thermal images of the inlet side and the outlet side and measuring pre cleaning operating conditions at the inlet side and the outlet side with a plurality of inlet sensors on the inlet side and a plurality of outlet sensors on the outlet side, wherein the plurality of inlet sensors include a temperature sensor, a relative humidity sensor, and a pressure sensor, and the plurality of outlet sensors include a temperature sensor, a relative humidity sensor, and a pressure sensor; 2) mixing water and a cleaning solution having ammonium bifluoride together to form a mixture; 3) applying a layer of the mixture directly onto the fins and outer surface of the matrix coil, said cleaning solution being noncorrosive; 4) allowing the mixture to set on the coils for a predetermined time that is sufficient so that contaminants formed on a surface of the heat exchanging coils are loosened and begin to dissolve; 5) heating and pressurizing water and the cleaning solution forming a wet steam mixture; 6) directing the wet steam mixture with a wand at exterior edges of the fins and into each of the plurality of channels as to penetrate the coil matrix between the inlet side and the outlet side; and 7) a post clean measuring step including measuring post cleaning operating conditions at the inlet side and the outlet side of the heat exchanger with the plurality of inlet sensors and the plurality of outlet sensors.