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HEATING AND AIR CONDITIONING
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HEATING AND AIR CONDITIONING
CONTENTS
page
page
COMPONENT SERVICE—XJ VEHICLES . . . . . . 23
COMPONENT SERVICE—YJ VEHICLES . . . . . . 32
COMPRESSOR SERVICE . . . . . . . . . . . . . . . . . . 19
GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 1
HEATING AND AIR CONDITIONING TEST
PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . 15
REFRIGERANT SERVICE AND PERFORMANCE
TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . . 37
WARNINGS, CAUTIONS AND SERVICE
PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 9
GENERAL INFORMATION
INDEX
page
A/C Components . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Heater and A/C Operation . . . . . . . . . . . . . . . . . . . . 1
Manifold Gauge Set . . . . . . . . . . . . . . . . . . . . . . . . 7
page
Refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Refrigerant Equipment . . . . . . . . . . . . . . . . . . . . . . 7
HEATER AND A/C OPERATION
HEATER—XJ
A blend-air heating system is used in XJ vehicles.
The temperature of heated air is controlled by regu-
lating the quantity of air flow through the heater
core. This is accomplished by blending outside air
with heated air from the heater core to obtain the de-
sired discharge temperature. A temperature control
lever on the heater control determines air flow
through the heater core. The lever uses a cable to op-
erate the blend-air door. This door controls air flow
through the core. Vacuum motors are used to actuate
and position the remaining door in the system.
On left hand drive (LHD) XJ vehicles a water valve
controls coolant flow to the heater core. The valve is
vacuum operated. When vacuum is applied, the valve
opens and coolant is directed through the heater core
and back to the engine. When the water valve is
closed (no vacuum applied) coolant flow bypasses the
heater core back to the engine.
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HEATING AND AIR CONDITIONING
HEATING SCHEMATIC—XJ
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HEATER—YJ
A blend-air heating system is used in YJ vehicles.
The blend-air system provides a constant flow of en-
gine coolant through the heater core.
HEATING AND AIR CONDITIONING
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The blower motor is operated by the control switch
(Fig. 1). The switch provides 3 blower speeds for in-
creased air flow in heat or defrost mode.
Fig. 1 Heater Control Panel
The air control lever (Fig. 1) operates a door in the
fresh air intake duct. The door controls the amount
of fresh air flow into the heater housing and core.
When the lever is in the OFF position, the intake
door is closed preventing air flow into the housing.
The temperature control lever (Fig. 1) determines
air flow through the heater core. The lever operates
the heater housing blend-air door which controls air
flow through the core.
DEFROSTING
The heater housing has a defroster door to divert
heated air to the defroster duct and outlets (Fig. 2).
Defrost air flow is controlled by the air control lever.
For defroster operation, the air control lever must
be moved to the defrost detent. The detent is identi-
fied by the defrost symbol on the control panel. In
this position, the defroster door diverts the heated
air from the core to the defroster duct outlets.
If air control lever is moved to any position be-
tween heat and defrost, the defroster door does not
close completely. In this mode, the door remains par-
tially open causing heated air to be divided equally
between the heat and defrost outlets.
FRESH AIR VENTILATION
The fresh air ventilating system (Fig. 3) is operated
by the air control lever. When the lever is moved to
VENT position, outside air from the cowl intake
flows into the heater housing. Incoming air is di-
rected into the vehicle interior through vent doors in
the housing.
A door in the intake duct controls air flow into the
duct. The door is operated by a vacuum motor. The
Fig. 2 Heating System Components
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HEATING AND AIR CONDITIONING
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Fig. 3 Fresh Air Intake System Components
motor is controlled by a vacuum switch in the heater
control panel. The vent air doors are opened and
closed by a cable and linkage operated by the air con-
trol lever. Fresh air intake occurs only when the le-
ver is in the VENT position.
A/C COMPONENTS
COMPRESSOR:
The SD7H15 Compressor is used
on all models. The purpose of the compressor is to
compress the low-pressure refrigerant vapor into a
high pressure, high temperature vapor. The compres-
sor is serviced as a assembly only.
CLUTCH PULLEY AND COIL:
They are
mounted on the compressor and providing a way to
drive the compressor. The compressor clutch and coil
are the only serviced parts on the SD7H15 compres-
sor. When the compressor is not in operation, the
pulley free wheels on the clutch hub bearing. When
the coil is energized the clutch plate is magnetically
engaged with the pulley and turns the compressor
shaft.
CONDENSER:
The condenser is located in front of
the engine radiator. Its function is to cool the hot
high pressure refrigerant gas. This causes it to con-
dense into high pressure liquid refrigerant.
EXPANSION VALVE:
The expansion valve is lo-
cated in the engine compartment on XJ vehicles. On
YJ vehicles it is located behind the A/C housing. Its
function is to meter refrigerant into the evaporator in
accordance with cooling requirements.
AIR CONDITIONING
The compressor increases the pressure and temper-
ature of the refrigerant. The heated refrigerant vapor
is pumped into the condenser where it is cooled by
air passing over the condenser fins. As the refriger-
ant cools in the condenser, it condenses into a liquid.
Still under high pressure, the liquid refrigerant
passes into the receiver. The receiver acts as a reser-
voir to furnish refrigerant to the expansion valve at
all times. From the receiver, the high pressure liquid
refrigerant passes to the expansion valve. The expan-
sion valve meters refrigerant into the evaporator.
The low pressure is maintained by the suction side of
the compressor. As it enters the evaporator, the re-
frigerant begins to absorb heat from the air passing
over the evaporator core. Having given up its heat to
boil the refrigerant, the air is cooled and passes into
the passenger compartment. From the evaporator the
vaporized refrigerant is drawn back to the compres-
sor to repeat the cycle.
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HEATING AND AIR CONDITIONING
AIR CONDITIONING SCHEMATIC—XJ
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