Jeep Cherokee 2000, Service Manual

Page: 1474 / 1528

However, evaporator capacity used to reduce the
amount of moisture in the air is not wasted. Wring-
ing some of the moisture out of the air entering the
vehicle adds to the comfort of the passengers.
Although, an owner may expect too much from their
air conditioning system on humid days. A perfor-
mance test is the best way to determine whether the
system is performing up to standard. This test also
provides valuable clues as to the possible cause of
trouble with the air conditioning system.
Review the Service Warnings and Precautions in
the front of this group before performing this proce-
dure. The air temperature in the test room and in
the vehicle must be a minimum of 21° C (70° F) for
this test.
(1) Connect a tachometer and a manifold gauge
set.
(2) Set the heater-A/C mode control switch knob in
the Recirculation Mode position, the temperature
control knob in the full cool position, and the blower
motor switch knob in the highest speed position.
(3) Start the engine and hold the idle at 1,000 rpm
with the compressor clutch engaged.
(4) The engine should be at operating temperature.
The doors and windows must be open.
(5) Insert a thermometer in the driver side center
A/C (panel) outlet. Operate the engine for five min-
utes.
(6) The compressor clutch may cycle, depending
upon the ambient temperature and humidity. If the
clutch cycles, unplug the low pressure cycling clutch
switch wire harness connector from the switch
located on the accumulator (Fig. 6). Place a jumper
wire across the terminals of the low pressure cycling
clutch switch wire harness connector.
(7) With the compressor clutch engaged, record the
discharge air temperature and the compressor dis-
charge pressure.
(8) Compare the discharge air temperature to the
Performance Temperature and Pressure chart. If the
discharge air temperature is high, see Refrigerant
System Leaks and Refrigerant System Charge in this
group.
Performance Temperature and Pressure
Ambient Air
Temperature 21° C
(70° F)
27° C
(80° F)
32° C
(90° F)
38° C
(100° F)
43° C
(110° F)
Air Temperature at
Center Panel Outlet -3 to 3° C
(27 to 38° F)
1 to 7° C
(33 to 44° F)
3 to 9° C
(37 to 48° F)
6 to 13° C
(43 to 55° F)
10 to 18° C
(50 to 64° F)
Evaporator Inlet
Pressure at Charge
Port
179 to 241 kPa
(26 to 35 psi)
221 to 283
kPa
(32 to 41 psi)
262 to 324
kPa
(38 to 47 psi)
303 to 365
kPa
(44 to 53 psi)
345 to 414 kPa
(50 to 60 psi)
Compressor Discharge
Pressure
1240 to 1655
kPa
(180 to 240
psi)
1380 to 1790
kPa
(200 to 260
psi)
1720 to 2070
kPa
(250 to 300
psi)
1860 to 2345
kPa
(270 to 340
psi)
2070 to 2690
kPa
(300 to 390 psi)
(9) Compare the compressor discharge pressure to
the Performance Temperature and Pressure chart. If
the compressor discharge pressure is high, see the
Pressure Diagnosis chart.
Fig. 6 Low Pressure Cycling Clutch Switch - Typical
1 – LOW PRESSURE CYCLING CLUTCH SWITCH
2 – ACCUMULATOR
24 - 10 HEATING AND AIR CONDITIONING
XJ
DIAGNOSIS AND TESTING (Continued)