Met with Alberto the dad, discussed if there were any issues and he said everything was good. He showed me the furnace, I opened up the evaporator cabinet to inspect the coils. They showed some rust and decay. Installed anti microbial tablets. I brushed and flushed the condensate drain lines. Checked the air filter, it needs replacement. Alberto said he would have his son replace it. Moved to the outside condenser. Opened up the disconnect switch along with the electrical junction box. Inspected, checked and cleaned all wiring connections. Connected the gauges and took readings. Found the unit low on refrigerant. Spoke with the customer regarding a leak check service with a possible coil replacement and a condenser acid wash. Alberto said he will discuss it with his son.