front JEEP CHEROKEE 1994 Service Repair Manual

MANIFOLD
The gauges are connected into the air conditioning
systems through a manifold. The manifold has 3 con-
nections (Fig. 1). The low side hose and fitting is con-
nected directly below the low side gauge. The high
side hose and fitting is connected below the high side
gauge.
The center connection of the manifold is used for
recovery and any other necessary service (Fig. 1).
Both the high and low sides of the manifold have
hand shutoff valves. The hand shutoff valves open or
close the respective gauge connections to the center
service connection or to each other (Fig. 1). The man-
ifold is constructed so that pressure will be indicated
on the gauges regardless of the hand valve position.
CONNECTING THE PRESSURE GAUGE AND
MANIFOLD ASSEMBLY
Remove the protective caps from the service valve
gauge ports and valve stems.
Close both of the hand valves on the gauge mani-
fold set.
Connect the compound gauge hose to the compres-
sor suction service valve gauge port (low-side).
Connect the high pressure gauge hose to the dis-
charge service valve gauge port (high-side).
If necessary, to facilitate installation of the gauge
set, loosen the service valve-to-compressor fitting and
rotate the service valve slightly. DO NOT allow the
hose to contact the engine or body components.
Tighten the service valve-to-compressor fitting to 34
NIm (25 ft. lbs.) torque. Tighten the flange-type ser-
vice valve screws to 20 NIm (15 ft. lbs.) torque.
Set both the service valve stems to the mid-position
or the cracked-position. The gauges will indicate
high and low side pressure respectively.Purge any air from the high side test hose by open-
ing the high side hand valve on the manifold for 3 to
5 seconds. The center connection on the manifold
must be open.
Purge any air from the low side test hose by open-
ing the low side hand valve on the manifold for 3 to
5 seconds. The center connection on the manifold
must be open.
The air conditioning system may be operated with
the gauge manifold assembly connected in this man-
ner. The gauges will indicate respective operative
pressures.
SERVICE VALVES
DESCRIPTION
The discharge (high pressure) and inlet (suction)
service valves are used for diagnosis and recovery of
the system. They are also used to isolate the system
during component Removal and Installation.
The service valves are three-position valves (Fig.
2). Normal operating position for the valve stem is
the back-seated (full-out) position. The stem is
turned counterclockwise to place it in this position.
The front seated (full-in) position is used to isolate
the compressor from the system. The stem is turned
clockwise to place it in this position.
Fig. 1 Pressure Gauge and Manifold Assembly Tool
C-3740-B
Fig. 2 Service Valve
JHEATING AND AIR CONDITIONING 24 - 3

In the mid-position the gauge port is open. This po-
sition is used for pressure testing and for recovery of
the system.
DISCHARGE SERVICE VALVE ADAPTERS
On occasion, a service hose may not fit a service
valve fitting. Adapters are available and can be used
to achieve service valve connection (Fig. 3).
SYSTEM DISCHARGE
(R-12) refrigerant is a chlorofluorocarbon (CFC)
that can contribute to the depletion of the ozone
layer in the upper atmosphere. To help protect the
ozone layer, an R-12 refrigerant recycling device
must be used. Use this device when it is necessary to
empty the refrigerant system. Contact an automotive
service equipment supplier for refrigerant recycling
equipment. Refer to the operating instructions pro-
vided with the recycling equipment for proper opera-
tion.
SYSTEM EVACUATION
The system must be evacuated whenever refriger-
ant has been discharged or when system refrigerant
level has become abnormally low. A vacuum pump is
used for the evacuation process.
The system must be evacuated to remove any mois-
ture or air that may have collected in the system. If
moisture is not removed from the system, it will com-
bine with R-12 to form a highly corrosive substance.
VACUUM PUMP
The Vacuum Pump Tool C-4069-B and motor
must be kept upright at all times to prevent oil
spills.
(1) Connect the Pressure Gauge and Manifold As-
sembly Tool C-3740-B to the service valves.
(2) Discharge the system.
(3) Connect the center service hose on the gauge
and manifold to the vacuum pump inlet fitting.
(4) Turn both manifold hand valves to the wide
open position.
(5) Start the vacuum pump and observe the vac-
uum gauge reading.
(6) Test the system for leaks as follows:
²Close the manifold hand valves.²Stop the vacuum pump and observe the vacuum
reading.
²If the system is leak-free, vacuum will hold steady
at the level indicated when the pump was stopped. If
vacuum remains steady for 3-5 minutes, resume and
continue evacuation for a minimum of 30 minutes.
²If the system has a leak, vacuum will fall off or
rapidly drop to a 0 reading. If a leak exists, partially
charge the system. Find and repair the leak and re-
sume evacuation.
(7) Continue operating the pump for a minimum of
30 minutes after attaining lowest vacuum indicated
on the gauge.
(8) Close the manifold hand valves and stop the
vacuum pump.
(9) Disconnect the center service hose from the
vacuum pump. The system is now ready for charging.
PORTABLE SERVICE STATION
The air conditioner service station is a self con-
tained, portable unit. It is equipped with a vacuum
pump, metering-charging cylinder, refrigerant sup-
ply, pressure and vacuum gauges, service hoses and
control valves (Fig. 4).
(1) Turn the station vacuum pump control switch
OFF (the switch is at the front of the station). The
pump control switch must be OFF before connecting
the station to an electrical power source.Fig. 3 Discharge Service Valve Adapters
Fig. 4 Portable Service Station
24 - 4 HEATING AND AIR CONDITIONINGJ

(18) Disconnect the charging hoses from the ser-
vice valves.
COMPRESSOR OIL LEVEL
The compressor oil level must be checked and ad-
justed if the system has been discharged rapidly, or
when a component has been replaced. If a replace-
ment compressor is being installed, it must be filled
with new compressor oil (Suniso 5GS, or equivalent).
The normal quantity of oil required for the com-
pressor and entire system is 136 ml (4.6 fluid oz.) for
SD 709 compressor. DO NOT overfill the compressor.
Excessive amounts of oil in the system will hinder
compressor operation and reduce A/C performance.
CAUTION: The compressor is a high speed unit.
Satisfactory operation is dependent on sufficient lu-
brication; however, excess oil will hinder A/C per-
formance.
Two oil level checking procedures are necessary.
Use Procedure (A) when the compressor is being re-
placed and the system was discharged properly (no
oil loss). Use Procedure (B) for routine maintenance
or when checking oil level after replacing a system
component.
In cases where rapid loss of refrigerant and oil
occurred, the system must be evacuated and
purged. Then the compressor must be filled with
the necessary amount of oil to fill the entire sys-
tem.
PROCEDURE A
(1) Remove the oil filler plug, discharge cap and
suction port caps from the original and replacement
compressor.
(2) Use a clean container to drain the oil from the
replacement compressor. Drain the oil through the
oil filler plug hole, the discharge and suction. Then
rotate clutch front plate several times to push the oil
on cylinder out to discharge chamber of cylinder
head and drain the oil from discharge port.
(3) Drain the oil from the original compressor into
a measuring cup or graduated beaker in the same
way as Step 2. Note the amount of oil drained.
(4) Fill the replacement compressor with the same
amount of oil drained from the original compressor
plus 30 ml (1 fluid oz.).
FOR EXAMPLE:ÐIf the old compressor contained
103.5 ml (3.5 fluid oz.) of oil, fill the replacement
compressor with a total of 133 ml (4.5 fluid oz.) of oil.
PROCEDURE B
(1) Start the engine and operate the engine at idle.
(2) Operate the air conditioning system for 10 min-
utes to return the maximum amount of oil in the sys-
tem to the compressor.(3) Stop the engine and disconnect the magnetic
clutch feed wire.
(4) Front-seat the discharge and suction service
valves.
(5) Determine the mounting angle.
(a) Position an Angle Gauge across the flat sur-
faces of the front mounting ears.
(b) Center the bubble.
(c) Read the mounting angle to the closest de-
gree.
(d) These vehicles should have 0É mounting an-
gle.
(6) Remove the oil filler plug. Position internal
parts by rotation of front plate counterweight to 30É
angle (Fig. 5).
(7) Insert the dipstick tool to its STOP position.
The Dipstick Tool is part of Tool Kit 7851. The stop
is the angle near the top of the dipstick. The bottom
surface of the angle must be flush with the surface of
the oil filler hole.
(8) Remove dipstick. Count increments of oil.
(9) Use mounting angle table to determine correct
oil level for the compressor (Fig. 6).
(10) If the increments read on the dipstick do not
match the table, add or subtract oil to the mid-range
value.
FOR EXAMPLE:ÐIf the mounting angle is 10É
and the dipstick increment is 3, add oil in 30 ml (1
fluid oz.) increments until 5 is read on dipstick.
(11) Check that the sealing O-ring is not twisted.
(12) Seat and O-ring must be clean.
Fig. 5 Check Oil Level
24 - 6 HEATING AND AIR CONDITIONINGJ

COMPRESSOR OVERHAUL
INDEX
page page
Compressor............................. 17
Compressor Isolation...................... 17
Description............................. 17Magnetic Clutch......................... 18
Purging Compressor of Air................. 17
DESCRIPTION
The A/C system uses a Sanden compressor. This
compressor is a 7 piston design. Designated the SD-
709, the compressor is mounted on the front right
side of the engine and is driven by a serpentine belt.
System lubrication is provided by 135cc615cc (4.6
cu. in.60.5 cu. in.) of 500 viscosity refrigerant oil.
The clutch used on the compressor consists of 3 ba-
sic components: the pulley, front plate and the field
coil. The pulley and field coil are attached to the
front head of the compressor with tapered snap rings.
The hub is keyed to the compressor shaft and is re-
tained on the shaft with a self-locking nut. Special
service tools are required to remove and install the
clutch plate on the compressor shaft.
COMPRESSOR ISOLATION
It is not necessary to discharge the system for com-
pressor removal. The compressor can be isolated from
the remainder of the system and eliminate the need
for recharging when performing compressor service.
(1) Connect pressure gauge and manifold.
(2) Close both gauge hand valves.
(3) Mid-position both service valves.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A DI-
RECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(4) Start the engine and operate the air condition-
ing system.
(5) Turn the suction service valve slowly clockwise
toward the front seated position.
(6) When pressure drops to zero, stop the engine
and compressor and quickly finish front-seating the
suction service valve.
(7) Front-seat the discharge service valve.
(8) Loosen the oil level check plug slowly to re-
lease any internal pressure in the compressor.
The compressor is now isolated from the remainder
of the system.
The service valves can be removed from the com-
pressor.
PURGING COMPRESSOR OF AIR
The compressor must be purged of air whenever it
has been isolated for an oil level check or other ser-
vice procedures without discharging the entire sys-
tem.
(1) Cap the service gauge ports on both of the ser-
vice valves.
(2) Back-seat the suction service valve to allow the
system refrigerant to enter the compressor.
(3) Place the discharge service valve in the mid-po-
sition or cracked-position.
(4) Loosen the discharge service valve gauge port
cap to permit the refrigerant to force any air out of
the compressor.
(5) Back-seat the discharge service valve and
tighten the gauge port cap.
(6) The compressor is now ready for service.
COMPRESSOR
REMOVAL
(1) Isolate the compressor.
(2) Disconnect negative cable from battery.
(3) Disconnect the clutch lead wire.
(4) Remove the discharge and inlet (suction) ser-
vice valves from the compressor. Plug or tape all the
openings.
(5) Remove the serpentine drive belt (refer to
Group 7, Cooling System for the proper procedure).
(6) Remove the bolts and lift the compressor from
the mounting bracket (Figs. 1 and 2).
INSTALLATION
If a replacement compressor is being installed;
check the oil level. Add or subtract oil as neces-
sary and install the magnetic clutch on the com-
pressor.
(1) If the mounting bracket was removed, install
the bracket to the block. Tighten the mounting bolts
to 27 NIm (20 ft. lbs.) torque.
(2) Install the compressor on the mounting
bracket. Tighten the bolts to 27 NIm (20 ft. lbs.)
torque.
(3) Install the serpentine drive belt (refer to Group
7, Cooling System for the proper procedure).
(4) Tighten the serpentine drive belt to the speci-
fied tension.
²New belt tensionÐ800-900 N (180-200 lb-f).
JHEATING AND AIR CONDITIONING 24 - 17

²Used belt tensionÐ623-712 N (140-160 lb-f).
(5) Remove the tape or plastic plugs from all the
suction and discharge openings and install the ser-
vice valves on the compressor.
(6) Connect the clutch lead wire.
(7) Connect negative cable to battery.
(8) Evacuate, charge and test the system for leaks.
MAGNETIC CLUTCH
The magnetic clutch consists of a stationary elec-
tro-magnetic coil and a rotating pulley and plate as-
sembly.
The electromagnetic coil is retained on the com-
pressor with a snap ring and is dimpled to maintain
its position.The pulley and plate assembly are mounted on the
compressor shaft.
When the compressor is not in operation, the pul-
ley free wheels on the clutch hub bearing. When the
coil is energized the plate is magnetically engaged
with the pulley and turns the compressor shaft.
REMOVAL
(1) Insert the 2 pins of the front plate spanner into
any 2 threaded holes of the clutch front plate (Fig.
3). Hold clutch plate stationary. Remove hex nut
with 19 mm (3/4 inch) socket (Fig. 3).
(2) Remove clutch front plate using puller. Align
puller center bolt to compressor shaft (Fig. 4). Thumb
tighten the puller bolts into the threaded holes.
(3) Turn center bolt clockwise with 19 mm (3/4
inch) socket until front plate is loosened.
Fig. 1 Compressor and Mounting Bracket (LH Drive
Vehicles)
Fig. 2 Compressor and Mounting Bracket (RH Drive
Vehicles)
Fig. 3 Hex Nut Removal
Fig. 4 Clutch Front Plate Removal
24 - 18 HEATING AND AIR CONDITIONINGJ

(4) Remove shaft key by lightly tapping it loose
with a slot screwdriver and hammer (Fig. 5).
(5) Remove the external front housing snap ring
by using spread type snap ring pliers (Fig. 6).
(6) Insert the lip of the jaws of the rotor puller into
the snap ring groove exposed in the previous step
(Fig. 7).
(7) Place rotor puller shaft protector over the ex-
posed shaft.(8) Install the puller plate and bolt (Fig. 8). 2 bolts
go through the plate and into the jaws. Finger
tighten bolts.
(9) Turn puller center bolt clockwise using 3/4 inch
socket until rotor pulley is free.
(10) Loosen coil lead wire from clip on top of com-
pressor front housing (Fig. 9).
(11) Using spread type snap ring pliers, remove
snap ring and field coil (Fig. 10).
Fig. 5 Shaft Key Removal
Fig. 6 External Snap Ring Removal
Fig. 7 Install Shaft Protector
Fig. 8 Install Puller Plate
JHEATING AND AIR CONDITIONING 24 - 19

INSTALLATION
(1) Install the field coil with the snap ring.
(2) Place coil lead wire under clip on top of com-
pressor front housing and tighten the retaining
screw.
(3) Support the compressor on the 4 mounting ears
at the compressor rear. If a vise is being used, clamp
only on the mounting ears. Never clamp on the com-
pressor body.
(4) Align rotor assembly squarely on the front
housing hub.(5) Using Rotor Installer Set, place the ring part of
the set into the bearing cavity (Fig. 11). Make cer-
tain the outer edge rests firmly on the rotor bearing
inner race.
(6) Place the tool set driver into the ring (Fig. 12).
(7) With a hammer, tap the end of the driver while
guiding the rotor to prevent binding. Tap until the
rotor bottoms against the compressor front housing
hub. Listen for a distinct change of sound during the
tapping process.
(8) Install external front housing snap ring with
spread type snap ring pliers.
(9) Install front plate assembly.
Fig. 9 Loosen Coil Lead Wire
Fig. 10 Snap Ring and Field Coil Removal
Fig. 11 Rotor Installer Set
Fig. 12 Tool Set Driver
24 - 20 HEATING AND AIR CONDITIONINGJ

²Check that original clutch shims are in place on
compressor shaft.
²Replace compressor shaft key.
²Align front plate keyway to compressor shaft key.
(10) Using shaft protector, tap front plate to shaft
until it has bottomed to the clutch shims (Fig. 13).
Listen for a distinct change of sound during the tap-
ping process.
(11) Replace shaft hex nut. Tighten the hex nut to
37 NIm (27 ft. lbs.) torque.
(12) Check air gap with feeler gauge (Fig. 14). The
specification is 0.406-0.787 mm (0.016-0.031 inch). If
air gap is not consistent around the circumference,
lightly pry up at the minimum variations. Lightly
tap down at points of maximum variation.The air gap is determined by the spacer shims.
When installing the original or a new clutch as-
sembly, try the original shims first. When install-
ing a new clutch onto a compressor that
previously did not have a clutch, use 0.040, 0.020,
and 0.005 shims from the clutch accessory sack.
(13) If the air gap does not meet the specification
given, add or subtract shims as required.
Fig. 13 Front Plate Installation
Fig. 14 Check Air Gap
JHEATING AND AIR CONDITIONING 24 - 21

AIR CONDITIONING
CONTENTS
page page
AIR CONDITIONING EQUIPMENT........... 4
AIR CONDITIONING PERFORMANCE TESTS . . 5
GENERAL INFORMATION.................. 1
REFRIGERANT LEAK TESTING, DISCHARGING,
EVACUATING AND CHARGING............ 8REFRIGERANT OIL....................... 9
SERVICE PRECAUTIONS.................. 3
WARNINGS AND CAUTIONS FOR R134A
SYSTEM.............................. 3
GENERAL INFORMATION
A/C COMPONENTS
COMPRESSORÐThe SD-709 Compressor is used
on all models. The compressor compresses the low-
pressure refrigerant vapor from the evaporator into a
high pressure, high temperature vapor. The compres-
sor is serviced as an assembly only.
CLUTCH PULLEY AND COILÐThey 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 SD-709 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.
CONDENSERÐThe 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.
FILTER-DRIERÐThe drier is used to remove con-
taminates and traces of moisture from the refriger-
ant system.
SIGHT-GLASSÐThe sight glass is located on top
of the filter drier. It is used as a diagnostic tool to ob-
serve refrigerant flow.
LOW-PRESSURE HIGH-PRESSURE CUT-OFF
SWITCHÐThe switch is located on the filter drier
and is wired in series with compressor clutch. When
the pressure drops down to 193 kPa (28 psi) the
switch interrupts the power to the compressor clutch.
When the pressure increases above 3100 to 3375 kPa
(450 to 490 psi) the switch interrupts the power to
the compressor clutch.
HIGH PRESSURE RELIEF VALVEÐThe valve
is located on the filter drier. The valve is used to pre-
vent excessive pressure up build of 3445 to 4135
kPag (500 to 600 psi) and above. This will prevent
damage to the compressor and other system compo-
nents.EXPANSION VALVEÐThe 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.
EVAPORATOR COILÐThe coil is located in the
A/C housing. Its function is to remove heat and de-
humidify the air before it enters the vehicle.
FIN SENSING CYCLING CLUTCH SWITCHÐ
The switch is attached to the evaporator coil. This
switch prevents condensate water on the evaporator
coil from freezing. It does this by cycling the com-
pressor clutch on and off. This switch is used onXJ
only
THERMOSTATÐThe thermostat is located in the
evaporator housing. Its function is to cycle the com-
pressor clutch to control temperature. The thermo-
stat is used on theYJonly.
REFRIGERANT LINESÐThe lines are used to
carry the refrigerant between the various system
components.
SERVICE PORTSÐThe high pressure service
port is located on the discharge line near the com-
pressor. The low pressure service port is located on
the suction line near the compressor. The compressor
no longer uses service valves.
After servicing the refrigerant system, always in-
stall service port caps.
REFRIGERANT
The vehicles use a new type of refrigerant called
R-134a. It is a non-toxic, non-flammable, clear color-
less liquified gas.
R-134a refrigerant is not compatible with R-12 re-
frigerant in an air conditioning system. A small
amount of R-12 in a R-134a system will cause com-
pressor failure, refrigerant oil sludge or poor A/C per-
formance.
JAIR CONDITIONING1

CAUTION: The fuel filler cap must be removed prior
to disconnecting any fuel system component.
CRANKCASE VENTILATION SYSTEM
All 2.5L 4 cylinder and 4.0L 6 cylinder engines are
equipped with a Crankcase Ventilation (CCV) system
(Figs. 8 or 9). The CCV system performs the same
function as a conventional PCV system, but does not
use a vacuum controlled valve.
On 4.0L engines, a molded vacuum tube connects
manifold vacuum to top of cylinder head (valve)
cover at dash panel end. The vacuum tube contains afixed orifice of a calibrated size. It meters the
amount of crankcase vapors drawn out of the engine.
On 2.5L engines, a fitting on drivers side of cylin-
der head (valve) cover contains the metered orifice. It
is connected to manifold vacuum.
A fresh air supply hose from the air cleaner is con-
nected to front of cylinder head cover on 4.0L en-
gines. It is connected to rear of cover on 2.5L
engines.
When the engine is operating, fresh air enters the
engine and mixes with crankcase vapors. Manifold
vacuum draws the vapor/air mixture through the
fixed orifice and into the intake manifold. The vapors
are then consumed during combustion.
PRESSURE RELIEF/ROLLOVER VALVE
All vehicles are equipped with a combination fuel
tank pressure relief and rollover valve (Fig. 10). This
dual function valve will relieve fuel tank pressure
and also prevent fuel flow through the fuel tank vent
hoses in the event of an accidental vehicle rollover.
Fig. 6 EVAP SystemÐTypical
Fig. 7 Air Cleaner VenturiÐTypical
Fig. 8 CCV SystemÐ2.5L EngineÐTypical
Fig. 9 CCV SystemÐ4.0L EngineÐTypical
JEMISSION CONTROL SYSTEMS 25 - 5