A/C System Abnormal Noise Symptom Diagnosis
There are various types of noise, ranging from those produced in the engine compartment to those from the passenger compartment, also from rumbling noises to whistling noises.
Abnormal Noise from Compressor
Condition Possible Cause Action
During compressor operation, a rumbling noise is heard proportional to engine revolutions
Inadequate clearance in piston area (piston or swash-plate)
Repair or replace compressor as necessary.
A loud noise is heard at a certain rpm, disproportionately to engine revolution
Loose or faulty compressor drive belt
Adjust drive belt tension, or replace belt.
Loose compressor mounting bolts
Retighten mounting bolts.
A loud rattle is heard at low engine rpm
Loose compressor clutch plate bolt
Retighten clutch plate bolt. Replace compressor if it was operated in this condition for a long time.

Abnormal Noise from Magnetic Clutch
Condition Possible Cause Action
A rumbling noise is heard when compressor is not operating
Worn or damaged bearings
Replace magnet clutch assembly.
A chattering noise is heard when compressor is engaged
Faulty clutch clearance (excessive)
Adjust clutch clearance.
Worn clutch friction surface
Replace magnet clutch assembly.
Compressor oil leaked from lip type seal
Replace lip type seal.
Contaminating the friction surface
Replace compressor body assembly.

Abnormal Noise from Tubing
Condition Possible Cause Action
A droning noise is heard inside vehicle, but not particularly noticeable in engine compartment
Faulty tubing clamps
Reposition clamps or increase the 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
Condition Possible Cause Action
Considerable vibration in condenser
Resonance from condenser bracket and body
Firmly insert a silencer between condenser bracket and body.

Abnormal Noise from Crankshaft Pulley
Condition Possible Cause Action
A large rattling noise is heard at idle or sudden acceleration
Loosen crankshaft pulley bolt
Retighten bolt.

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 A/C Evaporator
Condition Possible Cause Action
Whistling sound is heard from A/C evaporator
Depending on the combination of the interior/exterior temperatures, engine rpm and refrigerant pressure, the refrigerant flowing out of the expansion valve may, under certain conditions, make a whistling sound
At times, slightly decreasing refrigerant volume may stop this noise. Inspect expansion valve and replace if faulty.

Abnormal Noise from Blower Fan Motor
Condition Possible Cause Action
Blower fan motor emits a chirping sound in proportion to its speed of rotation
Worn or damaged motor brushes or commutator
Repair or replace blower fan motor
Fluttering noise or large droning noise is heard from blower fan motor
.Leaves or other debris introduced from fresh air inlet to blower fan motor
Remove debris and make sure that the screen at fresh air inlet is intact.