A growling noise is heard when the A/C compressor is disengaged. Which of the following is the most likely cause?

The presence of a growling noise when the A/C compressor is disengaged typically indicates an issue with the compressor's pulley bearing. The correct answer points specifically to worn compressor pulley bearings, which can produce a growling sound as they struggle to spin smoothly. This noise can occur under no load conditions, meaning when the compressor is not actively engaging the refrigerant system to provide cooling.

Typically, the compressor pulley is designed to provide a smooth rotational motion; however, if the bearings within this assembly wear down, it can lead to friction and movement that creates the growling sound. This wear may not manifest only during A/C operation; it can be noticeable when the compressor is not engaged due to the increasing resistance in the faulty bearings.

While the other options may potentially contribute to noise under different conditions, they are less likely to be the cause of a growling sound that specifically corresponds to the disengagement of the A/C compressor. For instance, loose clutch hubs tend to cause noise primarily during engagement, and worn internal compressor bearings would generally result in noise even when the compressor is operating. Dry blower motor bearings relate to a completely different system and would typically create a grinding or squealing noise associated with airflow rather than the A/C compressor function.