Came out to call for a system not cooling properly. Customer stated that they just got back from vacation and the thermostat was blank. They changed out the batteries and it came back on, but the AC wasn’t working still. I checked thermostat and found it not communicating with control board. I tested wired leads without thermostat face and the system cycled on properly. I also verified system operation in attic. Thermostat is needing to be replaced due to it not communicating. Went over options and pricing with customer, and they decided to go with the Honeywell WiFi thermostat. I installed the new thermostat and wired in common wire for constant power to the thermostat. Went over operation of thermostat with customer and set up control from mobile device. Went over having the system maintenance done due to it not being looked at in over 5 years. Customer signed up for blue plan. I gave customer filters, I inspected the blower assembly, motor, evaporator coil, compressor, fan motor,