Chrysler Dodge Caravan 2002 Manual page 2305

24 - 62 PLUMBING - FRONT
PLUMBING - FRONT (Continued)
CAUTION: All tools, including the refrigerant recy-
cling equipment, the manifold gauge set, and test
hoses should be kept clean and dry. Keep the work
area clean. Contamination of the refrigerant system
through careless work habits must be avoided. The
refrigerant system will remain chemically stable as
long as pure, moisture-free R-134a refrigerant and
refrigerant oil is used. Dirt, moisture, or air can
upset this chemical stability. Operational troubles
or serious damage can occur if foreign material is
introduced to the refrigerant system.
COMPRESSOR
DESCRIPTION
The compressor used on this vehicle can be one of
two models, depending upon the air conditioning sys-
tem in the vehicle. All vehicles use the Nippondenso
10S20 compressor. This compressor use an aluminum
swash plate, teflon coated pistons and aluminum
sleeveless cylinder walls. This compressor includes
an integral high pressure relief valve. The compres-
sor is secured low in the right front corner of the
engine compartment to a mounting bracket on the
cylinder block (2.4L engine), or directly to the cylin-
der block (3.3L and 3.8L engines) is integral to the
compressor. This compressor cannot be repaired. If
faulty or damaged, the entire compressor must be
replaced. The compressor clutch, pulley, and clutch
coil are available for service replacement.
OPERATION
The compressor is driven by the engine through an
electric clutch, drive pulley and belt arrangement.
The compressor is lubricated by refrigerant oil that is
circulated throughout the refrigerant system with the
refrigerant. The compressor draws in low-pressure
refrigerant vapor from the evaporator through its
suction port. It then compresses the refrigerant into
a high-pressure, high-temperature refrigerant vapor.
The compressor pumps high-pressure refrigerant
vapor to the condenser through the compressor dis-
charge port. The mechanical high pressure relief
valve is designed to vent refrigerant from the system
to protect against damage to the compressor or other
system components, caused by condenser air flow
restrictions or an overcharge of refrigerant. The valve
only vents enough refrigerant to reduce the system
pressure, then re-seats itself. The valve opens at a
discharge pressure of 3445 to 4135 kPA (500 to 600
psi) or above, and closes when a minimum discharge
pressure of 2756 kPa (400 psi) is reached.
DIAGNOSIS AND TESTING - COMPRESSOR
NOISE DIAGNOSIS
Excessive noise while the air conditioning compres-
sor is operating can be caused by loose compressor
mounts, a loose compressor clutch, or high operating
pressures in the refrigerant system. Verify compres-
sor drive belt condition, proper compressor mounting,
correct refrigerant charge level, and compressor head
pressure before compressor repair is performed.
With the close tolerances within the compressor, it
is possible to experience a temporary lockup. The
longer the compressor is inactive, the more likely the
condition is to occur. This condition is the result of
normal refrigerant migration within the refrigerant
system caused by ambient temperature changes. The
refrigerant migration may wash the refrigerant oil
out of the compressor.
NOTE: Prior to a vehicle being removed from ser-
vice or stored for more than two weeks, the com-
pressor should be operated to ensure adequate
refrigerant oil distribution throughout the system
components. Turn on the air conditioner for a min-
imum of five minutes with outside air and the high-
est blower speed selected.
BELT NOISE
If the compressor drive belt slips at initial start-up,
it does not necessarily mean the compressor has
failed. The following procedure can be used to iden-
tify a compressor drive belt noise problem.
• Start the vehicle and run at idle.
• Turn the air conditioner On and listen for belt
squeal.
• If belt squeal is heard, turn the air conditioner
Off immediately.
If the belt squeal stops when the air conditioner is
turned Off, perform the following repair procedures.
(1) Using an appropriate sized oil filter wrench or
a strap wrench, grasp the outer diameter of the com-
pressor clutch hub. While facing the compressor,
rotate the hub clockwise, then counterclockwise. If
the hub rotates, proceed to the next step. If the hub
will not rotate, the compressor is internally damaged,
and must be replaced.
(2) Turn the hub clockwise five complete revolu-
tions and remove the tool.
(3) Start the vehicle and run at idle.
(4) Turn the air conditioner On. Observe the com-
pressor and the system for normal operation, noting
cooling performance and noise levels. Operate for five
minutes before turning the air conditioner Off. If
acceptable cooling performance is observed during
compressor operation, the compressor does not need
to be replaced.
RS