Upon arrival inspected thermostat. Thermostat is displaying error code AO-01 Error code indicates an issue with external protection device or a problem with the indoor unit’s PCB (Printed circuit board). External protection device was checked. Green operating light is indicating that device is operating correctly. Wiring was checked for External device ( Surge Protector) Shut power @ outdoor unit to give system a hard reset. While outdoor is powered off. Inspect wiring @ indoor unit. Stripped and reconnected wiring. Check fuse and all other electrical components. Re-installed power to condenser after 5-10 minutes. Check thermostat operation once more. Thermostat still display same error code of AO-01 Tried to go through thermostat settings. Thermostat would not have system call for cooling. Thermostat goes back to display same error code. Customer had issue in the past where his other Daikin system gave same error code until PCB board was replaced. Customer is explaining that he had is