Komatsu 830E-AC Shop Manual page 955

Compressor
The compressor can fail due to shaft seal leaks (no
refrigerant in the system), defective valve plates,
bearings, or other internal parts or problems associ-
ated with high or low pressure, heat, or lack of lubri-
cation. Be sure the compressor is securely mounted
and the clutch pulley is properly aligned with the
drive pulley.
Use a mechanic's stethoscope to listen for noises
inside the compressor.
When installing a new compressor, the compres-
sor must be completely drained of its oil before
installation. Add 207 ml (7 oz.) of new PAG oil to
the compressor to ensure proper system oil
level. Failure to adjust the amount of oil in the
compressor will lead to excessive system oil and
poor A/C performance.
Under no circumstances should the A/C com-
pressor be stood upright onto the clutch assem-
bly. Damage to the compressor clutch will result,
leading to premature compressor failures.
Accumulator
The accumulator can not be serviced or repaired. It
must be replaced whenever the system is opened
for any service.
Clutch
Clutch problems include electrical failure in the clutch
coil or lead wire, clutch pulley bearing failure, worn or
warped clutch plate or loss of clutch plate spring tem-
per. Defective clutch assembly parts may be
replaced or the whole assembly replaced. If the
clutch shows obvious signs of excessive heat dam-
age, replace the whole assembly.
The fast way to check electrical failure in the lead
wire or clutch coil is to hot wire the coil with a fused
lead. This procedure enables you to bypass clutch
circuit control devices.
N04031 10/06
Clutch pulley bearing failure is indicated by bearing
noise when the A/C system is off or the clutch is not
engaged. Premature bearing failure may be caused
by poor alignment of the clutch and clutch drive pul-
ley.
Sometimes it may be necessary to use shims or
enlarge the slots in the compressor mounting bracket
to achieve proper alignment.
Excessive clutch plate wear is caused by the plate
rubbing on the clutch pulley when the clutch is not
engaged or the clutch plate slipping when the clutch
coil is energized. A gap that is too small or too large
between the plate and clutch pulley or a loss of clutch
plate spring temper are possible causes. The ideal
air gap between the clutch pulley and the clutch plate
is 1.02 ± 0.043 mm (0.023 to 0.057 in.). If the gap is
too wide, the magnetic field created when the clutch
coil is energized will not be strong enough to pull and
lock the clutch plate to the clutch pulley.
NOTE: Some compressors may be discarded
because it is suspected that internal components
within the compressor have seized. Ensure that
the compressor clutch is working properly before
discarding a compressor for internal seizure. The
normal compressor life span should be about
twice as long as the normal life span of the com-
pressor clutch.
It is important to note that often times a weak clutch
coil may be mistaken for a seized compressor. When
a coil's resistance has increased over time and the
magnetic field weakens, the coil may not be able to
pull the load of the compressor. Failure of the coil to
allow the compressor shaft to be turned, may appear
as though the compressor is locked up.
Before a compressor is dismissed as being seized, a
check for proper voltage to the coil should be per-
formed. In addition, the coil should be ohm checked
for proper electrical resistance. The coil should fall
within the following range:
12.0 ± 0.37 Ohms @ 20° C (68° F)
16.1 ± 0.62 Ohms @ 116° C (240° F)
The temperatures specified above are roughly typical
of a summer morning before first start-up and the
heat beside an engine on a hot day. At temperatures
in between those listed above, the correct resistance
is proportionate to the difference in temperature.
Operator Comfort N4-29