ON-VEHICLE SERVICE
HEATER, AIR CONDITIONING AND VENTILATION55-147
TEST PROCEDURES
1. Select a quiet area for testing.
2. Duplicate problem (customer complaint) as much as
possible.
3. Judge if the noise is abnormal (ie. it is important to
understand the characteristics of the vehicle and its normal
state to judge what is abnormal) - Compare with similar
vehicle if necessary.
4. Detail what and how noise occurs.
5. Find the noise source and verify its transmission by isolating
the subject part from the vehicle.
6. Repair the problem.
7. Explain and report your findings.
DETAILS OF A/C NOISE
POSSIBLE CAUSES, CHECKS AND REPAIRS
NOISE DESCRIPTION WHEN IT OCCURS SOURCE OF NOISE
Rumbling (Bearing noise) With A/C On or Off Magnetic clutch, idler pulley
Clang-Clack noise When compressor is engaged Magnetic clutch operation
Squawking (Belt sliding noise) When compressor is engaged V-belt
Whistling or Whooping noise Immediately after the A/C is
engaged.Expansion valve
Hissing or swishing noise When A/C is engaged, but
decreases as flow is stable Refrigerant flow
Rattling (Internal compressor) When compressor is operating Compressor internal part
Wooing (Resonant noise) With A/C On, occurs at certain
speed.Resonance of accessories
Cooing (Discharge pulsation
noise)With A/C On or Off Resonating noise with the vehicle
body
NOISE DESCRIPTION POSSIBLE CAUSE CHECK REPAIR
Rumbling (Bearing
noise)Bearing damage in rotor Manual rotation of bearing Replace compressor
Rotor slipping on boss Wear on compressor boss
surfaceReplace compressor
Bearing damage in pulley Check alignment between
pulleysReplace compressor
Clang-Clack noise Hub to stator misaligned Wear on inner clutch face Replace compressor
Gap between clutch
surface is too largeCheck Air gap is within
specificationReplace compressor
Squawking (Belt sliding
noise)Oil/water between the belt
and rotor surfaceOil and water
contaminationClean
Low belt tension Belt tension Reset or Replace belt and
set tension to correct
specification
Whistling or Whooping
noiseVibration of expansion
valveExpansion valve Replace TX valve
