PERFORMANCE TEST PROCEDURE
Review Safety Precautions and Warnings in this
group before proceeding with this procedure. Air tem-
perature in test room and on vehicle must be 21° C
(70°F) minimum for this test.
NOTE: When connecting the service equipment
coupling to the line fitting, verify that the valve of
the coupling is fully closed. This will reduce the
amount of effort required to make the connection.
(1) Connect a tachometer and manifold gauge set.
Attach a thermocouple to the evaporator inlet line.
(2) Set control to A/C, RECIRC, and PANEL, tem-
perature lever on full cool and blower on high.
(3) Start engine and hold at 1000 rpm with A/C
clutch engaged.
(4) Engine should be warmed up with doors and
windows closed.
(5) Insert a thermometer or place a thermocouple
in the left center A/C outlet and operate the engine
for five minutes. The A/C clutch may cycle depending
on ambient conditions.
(6) With the A/C clutch engaged, compare the dis-
charge air temperature to the evaporator inlet line
temperature. The evaporator inlet line temperature
should be no more than 12°C (10°F) cooler than the
discharge air temperature.
(7) If the discharge air temperature fails to meet
the specifications. Refer to the System Charge Level.
COMPRESSOR CLUTCH COIL
(1) Verify battery state of charge.
(2) Connect an ammeter (0-10 ampere scale) in
series with the clutch coil terminal. Use a volt meter
(0-20 volt scale) with clip leads measuring voltage
across the battery and A/C clutch.
(3) With A/C control in A/C mode and blower at
low speed, start the engine and run at normal idle.
(4) The A/C clutch should engage immediately and
the clutch voltage should be within 2 volts of the bat-
tery voltage. If the A/C clutch does not engage, test
the fusible link.
(5) The A/C clutch coil is acceptable if the current
draw is 2.0 to 4.15 amperes at 11.5 to 12.5 volts at
clutch coil. This is with the work area temperature at
21°C (70°F). If voltage is more than 12.5 volts, add
electrical loads by turning on electrical accessories
until voltage reads below 12.5 volts.
(6) If coil current reads zero, the coil is open and
should be replaced. If the ammeter reading is 5
amperes or more, the coil is shorted and should be
replaced. If the coil voltage is not within two volts of
the battery voltage, test clutch coil feed circuit for
excessive voltage drop.
COMPRESSOR NOISE TEST
When investigating an air conditioning related
noise, you must first know the conditions when the
noise occurs. These conditions are: weather, vehicle
speed, in gear or neutral, engine temperature, or any
other special condition.
Noises that develop during air conditioning opera-
tion can often be misleading. For example: what
sounds like a failed front bearing or connecting rod,
may be caused by loose bolts, nuts, mounting brack-
ets, or a loose clutch assembly. Improper drive belt
tension can cause a misleading noise when compres-
sor is engaged. The noise may not occur when com-
pressor is disengaged.
Drive belt(s) are speed sensitive. At different
engine speeds and depending upon belt tension,
belt(s) can develop noises that are mistaken for a
compressor noise.
(1) Select a quiet area for testing. Duplicate condi-
tions as much as possible. Switch compressor on and
off several times to clearly identify compressor noise.
Listen to compressor clutch while engaged and disen-
gaged.
(2) To duplicate high-ambient condition (high-head
pressure), restrict air flow through condenser. Install
manifold gauge set to make sure discharge pressure
doesn’t exceed 2070 kPa (300 psi).
(3) Tighten ALL compressor mounting bolts, clutch
mounting bolt, clutch coil mounting screws
(4) Check refrigerant hoses for rubbing or interfer-
ence which can cause unusual noises.
(5) Check refrigerant charge (refer to Charging the
System).
(6) Check compressor noise as in Step 1.
(7) If noise still exists, loosen compressor mount-
ing bolts and torque. Repeat Step 1.
(8) If noise continues, replace compressor and
repeat Step 1.
CONTROL MODULE
The control switch and timer circuit may be tested
in the vehicle with or without scan tool (DRB).
TESTING WITH SCAN TOOL
If using the scan tool, refer to the proper Body
Diagnostic Procedures Manual.
TESTING WITHOUT SCAN TOOL
(1) Remove the control switch from console and
disconnect control switch (Fig. 2).
(2) Using a ohmmeter, check leads between Pins 5
and 8 of the 8-Way connector. Turn the control mod-
ule to each position shown on Control Module Test
table. The resistance reading should be within the
specifications shown. If not OK, replace the control
module. If OK, check:
• Blown fuse
• Cut wire
24 - 6 HEATING AND AIR CONDITIONING JA
DIAGNOSIS AND TESTING (Continued)
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