Over the years I've had several local HVAC companies provide seasonal maintenance of the heat pumps and propane furnace in my house. It seems that every technician--even within the same company--does different things. One tested a capacitor. Another hosed out the compressors outside. Some open the air handler up and vacuum it. They all clean the burners, check/clean the filters, and make sure the condensation drain is clear. What should they be doing each visit?