Performed 2 ac pms Visually inspected indoor evap coil and blower compartment Checked all electrical connections and safeties Checked volts and amps Visually inspected air filter Replaced both filters with customer supplied Rinsed condenser coil Blew out drain line and poured water to ensure properly draining Tested condensate pump Checked refrigerant levels Checked capacitor Took temps While performing the maintenance we found the customer had the second floor system replaced since the last maintenance. We found the refrigerant line connections were made with silver solder instead of braze. Manufacturers say in the install manual not to use silver solder since it is not rated for higher pressure refrigerants. Also found the second floor unit was low on refrigerant. The manufacturer calls for 10*sub and the u it was only at 2.5*. After getting customer authorization we added 11oz R410A to the system bringing the subcooling up to 13*. Unit is working properly