What happens when an air handler goes bad?

When a residential indoor air handler goes bad and suffers total mechanical or electrical failure, your entire HVAC system loses its ability to circulate conditioned air throughout your home's ductwork. Because the air handler houses the blower motor, electrical control board, and air filter, a failure means no air will blow from your supply vents even if your outdoor compressor is actively running. You may notice complete silence from the unit, a burning electrical odor from a fried motor winding, or tripped circuit breakers. Without airflow, indoor temperatures will spike in summer or plunge in winter. To troubleshoot, turn off power and check motor capacitors. You can verify that the air handler is completely dead when confirmed line and low-voltage power fail to engage the blower motor, requiring professional replacement.