Okay - cut and past from Manual pg 24-10
TESTS
(1) Verify the battery state of charge (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM/BATTERY -
DIAGNOSIS AND TESTING).
(2) Connect an ammeter (0 to 10 ampere scale
selected) in series with the clutch coil feed terminal.
Connect a voltmeter (0 to 20 volt scale selected) to
measure voltage across the battery and the clutch
coil.
(3) With the A/C-heater control in the A/C mode
and the blower motor at low speed, start the engine
and allow it to run at a normal idle speed.
(4) The A/C compressor clutch should engage
immediately, and the clutch coil supply voltage
should be within two volts of the battery voltage. If
the coil supply voltage is OK, go to Step 5. If the coil
supply voltage is not within two volts of battery voltage,
test the clutch coil feed circuit for excessive voltage
drop and repair as necessary. If there is no
voltage reading at the clutch coil, use a DRB III t
scan tool and refer to appropriate diagnostic information
for testing of the compressor clutch circuit and
PCM control. The following components must be
checked and repaired as required before you can complete
testing of the clutch coil:
² Fuses in the junction block (JB) and the power
distribution center (PDC)
² A/C heater mode control
² A/C clutch relay
² A/C high pressure switch (diesel engine)
² A/C low pressure switch
² Powertrain control module (PCM) or the engine
control module (ECM) (depending on engine application)
(5) For the acceptable A/C clutch coil current draw
specifications refer to 24 - HEATING & AIR CONDITIONING
- SPECIFICATIONS. Specifications apply
for a work area temperature of 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.
(a) If the A/C clutch coil current reading is zero,
the coil is open and must be replaced.
(b) If the A/C clutch coil current reading is above
specifications, the coil is shorted and must be
replaced
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