Jeep Cherokee 2000, Service Manual

Page: 1479 / 1528

to be certain that the discharge pressure does not
exceed 2760 kPa (400 psi).
(4) Check the refrigerant system plumbing for
incorrect routing, rubbing or interference, which can
cause unusual noises. Also check the refrigerant lines
for kinks or sharp bends that will restrict refrigerant
flow, which can cause noises. See Suction and Dis-
charge Line in the Removal and Installation section
of this group for more information.
(5) If the noise is from opening and closing of the
high pressure relief valve, evacuate and recharge the
refrigerant system. See Refrigerant System Evacuate
and Refrigerant System Charge in the Service Proce-
dures section of this group. If the high pressure relief
valve still does not seat properly, replace the com-
pressor.
(6) If the noise is from liquid slugging on the suc-
tion line, replace the accumulator. See Accumulator
in the Removal and Installation section of this group
for the procedures. Check the refrigerant oil level
and the refrigerant system charge. See Refrigerant
Oil Level and Refrigerant System Charge in the Ser-
vice Procedures section of this group. If the liquid
slugging condition continues following accumulator
replacement, replace the compressor.
(7) If the noise continues, replace the compressor
and repeat Step 1.
COMPRESSOR CLUTCH COIL
For circuit descriptions and diagrams, refer to
8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams. The battery must be fully-charged
before performing the following tests. Refer to Group
8A - Battery for more information.
(1) Connect an ammeter (0 to 10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0 to 20 volt scale) with clip-type leads for measuring
the voltage across the battery and the compressor
clutch coil.
(2) With the heater-A/C mode control switch in any
A/C mode, and the blower motor switch in the lowest
speed position, start the engine and run it at normal
idle.
(3) The compressor clutch coil voltage should read
within two volts of the battery voltage. If there is
voltage at the clutch coil, but the reading is not
within two volts of the battery voltage, test the
clutch coil feed circuit for excessive voltage drop and
repair as required. If there is no voltage reading at
the clutch coil, use a DRB scan tool and the proper
Diagnostic Procedures manual for testing of the com-
pressor clutch circuit. The following components
must be checked and repaired as required before you
can complete testing of the clutch coil:
•
Fuses in the junction block and the Power Dis-
tribution Center (PDC)
•
Heater-A/C mode control switch
•
Compressor clutch relay
•
High pressure cut-off switch
•
Low pressure cycling clutch switch
•
Powertrain Control Module (PCM).
(4) The compressor clutch coil is acceptable if the
current draw measured at the clutch coil is 2.0 to 3.9
amperes with the electrical system voltage at 11.5 to
12.5 volts. This should only be checked with the work
area temperature at 21° C (70° F). If system voltage
is more than 12.5 volts, add electrical loads by turn-
ing on electrical accessories until the system voltage
drops below 12.5 volts.
(a) If the clutch coil current reading is four
amperes or more, the coil is shorted and should be
replaced.
(b) If the clutch coil current reading is zero, the
coil is open and should be replaced.
COMPRESSOR CLUTCH RELAY
RELAY TEST
The compressor clutch relay (Fig. 8) is located in
the Power Distribution Center (PDC). Refer to the
PDC label for relay identification and location.
Remove the relay from the PDC to perform the fol-
lowing tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75
6
5 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, see Relay Circuit Test in the Diagno-
sis and Testing section of this group. If not OK,
replace the faulty relay.
RELAY CIRCUIT TEST
For circuit descriptions and diagrams, refer to
8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams.
(1) The relay common feed terminal cavity (30) is
connected to fused battery feed. There should be bat-
tery voltage at the cavity for relay terminal 30 at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the PDC as required.
(2) The relay normally closed terminal (87A) is not
used in this application. Go to Step 3.
(3) The relay normally open terminal cavity (87) is
connected to the compressor clutch coil. There should
be continuity between this cavity and the A/C com-
pressor clutch relay output circuit cavity of the com-
XJ
HEATING AND AIR CONDITIONING 24 - 15
DIAGNOSIS AND TESTING (Continued)