Abnormal Noise Symptom Diagnosis of HVAC System

Abnormal Noise from Blower Motor

Condition	Possible Cause	Action
Blower motor emits chirping sound in proportion to its speed	Worn or damaged motor brushes or commutator	Replace blower motor.
Blower motor emits fluttering noise or large droning noise	Leaves or other debris in air inlet or on blower motor	Remove debris and check screen at fresh air inlet.