Abnormal Noise Symptom Diagnosis of A/C System

Abnormal Noise from Compressor

Condition	Possible Cause	Action
During compressor operation, a rumbling noise is heard as to engine speed increases	Inadequate clearance in scroll area	Replace compressor.
Loud noise is heard at certain rpm, irrespective of greatness of speed in	Loose or faulty compressor drive belt (petrol model)	Check compressor drive belt.
	Loose or faulty generator drive belt (diesel model)	Check generator drive belt.
	Loose compressor mounting bolts	Retighten mounting bolts.
Loud rattle is heard at low engine rpm	Loose compressor clutch plate nut (petrol model)	Replace compressor if it has operated in rattling condition for a long time. Retighten clutch plate nut.
Loud rattle is heard at low engine rpm	Faulty compressor pulley (diesel model)	Check compressor pulley.

Abnormal Noise from Magnet Clutch (Petrol Model)

Condition	Possible Cause	Action
Rumbling noise is heard when compressor is not in operation	Worn or damaged bearings	Replace magnet clutch assembly.
Chattering noise is heard when compressor is in operation	Faulty magnet clutch clearance (excessive clearance)	Adjust magnet clutch clearance.
	Worn magnet clutch friction surface	Replace magnet clutch assembly.
	Compressor oil leakage from shaft seal, contaminating friction surface	Replace compressor body assembly.

Abnormal Noise from Tubing

Condition	Possible Cause	Action
Droning noise is heard from inside of the vehicle, but not particularly noticeable in engine compartment	Faulty tubing clamps	Reposition clamps or increase number of clamps.
	Resonance caused by pulsation from variations in refrigerant pressure	Attach a silencer to tubing, or modify its position and length.

Abnormal Noise from Condenser Assembly

Condition	Possible Cause	Action
Considerable vibration in condenser assembly	Resonance from condenser assembly bracket and body	Firmly insert a silencer between condenser assembly bracket and body.

Abnormal Noise from Crankshaft Pulley

Condition	Possible Cause	Action
Large rattling noise is heard at idle or sudden acceleration	Loosen crankshaft pulley bolt	Retighten bolt. •M16A model: •K14C model: •D16AA model:

Abnormal Noise from Tension Pulley

Condition	Possible Cause	Action
Clattering noise is heard from pulley	Worn or damaged bearing	Replace tension pulley.
Pulley cranks upon contact	Cracked or loose bracket	Replace or retighten bracket.

Abnormal Noise from Evaporator

Condition	Possible Cause	Action
Whistling sound is heard from evaporator	Depending on the combination of the interior / exterior temperatures, engine rpm and refrigerant pressure, the refrigerant flowing out of the expansion valve may generate whistling sound.	Slightly decreasing amount of refrigerant may stop this noise. Check expansion valve and replace it if faulty.

Abnormal Noise from Blower Motor

Condition	Possible Cause	Action
Blower motor emits a chirping sound in proportion to its speed of rotation	Worn or damaged motor brushes or commutator	Replace blower motor.
Fluttering noise or large droning noise is heard from blower motor	Leaves or other debris introduced from fresh air inlet to blower motor	Remove debris and check that screen at fresh air inlet is intact.