How do you know if your air handler is bad?

Determining whether your residential indoor air handler has failed completely involves observing severe operational breakdowns and lack of airflow throughout your home. Key signs of a bad air handler include complete silence from the indoor unit when your thermostat calls for heating or cooling, a burning electrical odor coming from the cabinet caused by a burnt-out blower motor winding, or persistent tripping of the dedicated electrical circuit breaker whenever the fan attempts to start. You may also notice that your indoor supply vents produce zero airflow even though the outdoor condenser is running. To troubleshoot safely, turn off power at the breaker and inspect the blower motor and capacitors. You can verify that the air handler is dead when confirmed 24-volt control signals and line voltage fail to engage the blower motor, indicating replacement is required.