Diagnostics of indoor unit of HVAC system based on sound signatures

A method for heating, ventilation, and air conditioning (HVAC) system diagnostics includes sending a first instruction to a thermostat to shut down an HVAC system. A user is instructed to minimize background noise. A second instruction is sent to the thermostat to turn on the HVAC system. A third instruction is sent to the thermostat to set a temperature setpoint below or above a value of a room temperature. Indoor unit sound data is captured for a second time period. The baseline sound data is subtracted from the indoor unit sound data to determine normalized indoor unit sound data. Expected sound signatures of the indoor unit are identified. The normalized indoor unit sound data is compared to the expected sound signatures. In response to determining that an expected sound signature for a blower is missing from the normalized indoor unit sound data, it is determined that the blower has failed.