1988 JEEP CHEROKEE Service Repair Manual

Fig. 3: Assembling Ford Spring-Coupling Fitting
3) Lubricate both sides of fitting with clean refrigeration
oil. Assemble the fitting by pushing together with a slight twisting
motion. Check to make sure spring is over flared end of female
fitting.
PLACING SYSTEM IN OPERATION
After component replacement and/or system servicing has been
completed and all connections have been made, proceed as follows:
1) Evacuate the system using vacuum pump.
2) Charge the system with R-12. See REFRIGERANT CAPACITY in
the A/C SYSTEM SERVICE SPECIFICATIONS in this article.
3) Leak test the system, with particular attention to all new
connections and components.
4) Make a performance test of the system. Never assume that a
recharging has automatically corrected a problem.
DIAGNOSTIC PROCEDURES
Diagnosis is an important first step in A/C system servicing.
To save time and effort, systems should be carefully checked to
identify the causes of poor performance. By using the following
diagnostic charts, defective components or system damage can be
quickly located. To identify problems that are specific to one system,
refer to the repair sections of this article. The charts in this
article apply to all systems.
PREPARATION FOR TESTING
1) Attach Low and High side gauges.
2) Start engine and allow it to warm up.
3) Set system to COOL and blower to HIGH.
4) Open car doors and hood.
5) Run at fast idle for 2-3 minutes.

ALTITUDE PRESSURE VARIATIONS
ALTITUDE PRESSURE VARIATIONS








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Altitude (Ft. Absolute Pressure Gauge Altitude
Above Sea Level) of Atmosphere(psi) Correction (1) (psi)
0 ...................... 14.7 ........................ 0
1000 ................... 14.2 ..................... -0.5
2000 ................... 13.7 ..................... -1.0
3000 ................... 13.2 ..................... -1.5
4000 ................... 12.7 ..................... -2.0
5000 ................... 12.2 ..................... -2.5
6000 ................... 11.7 ..................... -3.0
7000 ................... 11.3 ..................... -3.4
8000 ................... 10.9 ..................... -3.8
9000 ................... 10.5 ..................... -4.2
10,000 ................. 10.1 ..................... -4.6
(1) - Subtract correction shown from gauge readings.









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ALTITUDE VACUUM VARIATIONS








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Altitude (Ft. Complete Vacuum Gauge Altitude
Above Sea Level) (In. Hg) Correction (In. Hg)
0 ...................... 29.92 ....................... 0
1000 ................... 28.92 .................... +1.0
2000 ................... 27.82 .................... +2.1
3000 ................... 26.82 .................... +3.1
4000 ................... 25.82 .................... +4.1
5000 ................... 24.92 .................... +5.0
6000 ................... 23.92 .................... +6.0
7000 ................... 23.02 .................... +6.9
8000 ................... 22.22 .................... +7.7
9000 ................... 21.32 .................... +8.6
10,000 ................. 20.52 .................... +9.4
(1) - Add correction shown to gauge readings.









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OPERATIONAL TEST GAUGE READINGS
Normal System Operating Pressures (PSI) (1)









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Low Side Gauge High Side Gauge
Application (Suction) (Discharge)
Thermostatic Switch .... 5-24 .................. 208-250
(1) - Pressure readings given are for a system in good
operating condition, at sea level and an ambient
temperature of 80
F (27C).








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A/C SYSTEM PERFORMANCE CHECK TABLE
AIR CONDITIONING SYSTEM PERFORMANCE CHECK








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PERFORM TESTS: SHOULD BE: IF:








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Temperature Check Temperature Check Is

* Switch to LOW
blower.
* Close doors. Too warm - Check control
lever operation, heater
water valve, cooling
system and gauge readings.
* Check outlet
temperature. 35-45
F (1.7-7.2C)








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Visual Check Visual Check Shows:
* Compressor Quiet, No Leaks Noisy - Check belts, oil
level, seals, gaskets,
reed valves.
* Condenser Free of Obstructions Blocked - Clean off.
Plugged - Flush or
replace.
* Receiver-Drier Dry and warm to Frosty - Check for re-
touch striction, replace
Desicant.
* Sight Glass Clear or few bubbles Bubbly, foamy or streaks -
Check gauge readings.
* High Side Lines Dry and warm to Frosty or very hot - Check
touch for restriction or
overcharge.
* Low Side Lines Dry and cool to Frosty or warm - Check for
touch restriction, low charge or
bad valve.
* Expansion Valve Dry Frosty - Check for moisture
or restriction. Check
sensing bulb.
* STV Dry and cool to Frosty or warm - Check
touch gauge readings for valve
malfunction.
* Evaporator Dry and cold to Freezing or warm - Check
touch expansion valve, STV or
thermo switch.









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Gauge Readings Gauge Readings are:
* High Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.
* Low Side Gauge See Pressure Chart Above or below normal - See
A/C DIAGNOSIS.









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PRESSURE CHARTS

Fig. 4: Ambient Temperature/Pressure

Fig. 5: Evaporator Temperature/Pressure
A/C SYSTEM DIAGNOSIS WITH GAUGES
DIAGNOSIS WITH GAUGES - SYSTEMS WITH INSUFFICIENT OR NO COOLING








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LOW SIDE HIGH SIDE OTHER SYMPTOMS(1) DIAGNOSIS
GAUGE GAUGE
Normal Normal No or few bubbles in sight Some Air and
glass. High side gauge may Moisture in System
go high. Low side gauge
does not fluctuate with
compressor on/off cycle.









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Normal Normal Cools okay in morning but Excessive Moisture
not during hot part of day. in System

Tiny bubbles in sight
glass. Discharge air warm
when low side gauge drops
into vacuum.









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Normal Normal Thermostatic switch system Defective Thermo-
only-compressor cycles off static Switch
and on too rapidly.









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Normal Normal Cycling clutch systems Misadjusted Thermo
to High only-Compressor doesn't static Switch or
turn on soon enough. Defective Pressure
Discharge air becomes Sensing Switch
warm as low side
pressure rises.









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Low Low Bubbles in sight glass. Low R-12 Charge
Outlet air slightly cool.









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Low Low Sight glass clear or oil- Excessively Low
streaked. Outlet air very R-12 Charge
warm.









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Low Low Outlet air slightly cool. Expansion Valve
Sweating or frost at Stuck Closed.
expansion valve. Screen Plugged or
Sensing Bulb
Malfunction









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Low Low Outlet air slightly cool. Restriction on
High side line cool to High Side.
touch. Sweating or frost
on high side.









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Low High Evaporator outlet pipe STV Stuck Open
cold. Low side goes into
vacuum when blower is
disconnected.









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High Low Evaporator outlet pipe STV Stuck Open
warm. Outlet air warm.









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High Low Noise from compressor Compressor
Malfunction









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High High Outlet air warm. Condenser
Liquid line very hot. Malfunction or
Bubbles in sight glass. R-12 Overcharge









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High High Outlet air slightly cool. Large Amount of
Bubbles in sight glass. Air and Moisture
in System.









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High High Outlet air warm. Expansion Valve
Evaporator outlet Stuck Open.
sweating and frost.









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(1) - If equipped with a low refrigerant charge protection system,
compressor operation may have stopped.









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A/C SYSTEM SERVICE SPECIFICATIONS

REFRIGERANT OIL & R-12 CAPACITY TABLE








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(1) Oil R-12
Application Ounces Ounces
Eagle ......................... 5.7 ........................... 36
(1) - Total system capacity, unless otherwise noted.









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SYSTEM REFRIGERANT CAPACITIES








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Application Pounds Ounces
Eagle
Medallion & Premier ..... 1 7/8 .............. 29
Summit (FX105V) ......... 2 1/4 .............. 36
Jeep
CJ Models ............... 2 1/2 .............. 40
Comanche .................. 2 ................ 32
All Other Jeep Models . 2 1/4 .............. 36









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COMPONENT OIL REPLACEMENT QUANTITIES








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Component Ounces
Accumulator ................................... (1)
Condenser ....................................... 1
Evaporator ...................................... 1
Receiver-Drier .................................. 1
Compressor
Premier ....................................... (1)
Medallion ..................................... 5.7
Grand Wagoneer .................................. 8
All Other Jeep Models ........................... 7
(1) - Add amount drained plus 1 ounce.









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COMPRESSOR BELT TENSION (Lbs.) (1)








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Application New Belt Used Belt
Eagle
1.4L & 1.7L ............ 120-160 ......... 90-115
Jeep
Regular Belt ........... 125-155 ......... 90-115
Serpentine Belt ........ 180-200 ........ 140-160
(1) - Using standard strand tension gauge.









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COOLING SYSTEM CAPACITIES (1)








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Application Quarts (Liters)
Eagle
Medallion & Premier
With A/C .............................. 4.8 (4.5)

Without A/C ........................... 4.4 (4.2)
Jeep
Cherokee & Wagoneer (2)
4-Cylinder ........................... 10.0 (9.5)
V6 .................................. 12.0 (11.4)
CJ & Scrambler
4-Cylinder ............................ 9.0 (8.5)
6-Cylinder ........................... 10.5 (9.9)
Grand Wagoneer & Truck (3)
6-Cylinder .......................... 12.5 (11.8)
V8 .................................. 15.5 (14.7)
(1) - May vary +/- 15% due to system variations.
(2) - Includes 2.3 qts. (2.2L) in recovery bottle.
(3) - Includes 1 qt. (.9L) for heater.









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