A/C Clutch Control Circuit Diagnosis; Circuit Description; Diagnostic Aids - Isuzu 2000 Trooper Workshop Manual

Circuit Description

When air conditioning and blower fan are selected, and if
the system has a sufficient refrigerant charge, a 12-volt
signal is supplied to the A/C request input of the
powertrain control module (PCM).
signal may be temporarily canceled during system
operation by the electronic thermostat in the evaporator
case. When the A/C request signal is received by the
PCM, the PCM supplies a ground from the compressor
clutch relay if the engine operating conditions are within
acceptable ranges. With the A/C compressor relay
energized, voltage is supplied to the compressor clutch
coil.
The PCM will enable the compressor clutch to engage
whenever A/C has been selected with the engine running,
unless any of the following conditions are present:
D The throttle is greater than 90%.
D The ignition voltage is below 10.5 volts.
D The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A/C Clutch Control Circuit Diagnosis

The A/C request
D The engine coolant temperature (ECT) is greater
than 125 °C (257 °F).
D The intake air temperature (IAT) is less than 5°C
(41°F).
D The power steering pressure switch signals a high
pressure condition.

Diagnostic Aids

To diagnose an the intermittent fault, check for following
conditions:
D Poor connection at the PCM–Inspect connections for
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.
D Damaged harness–Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C.
malfunction will indicate the source of the intermittent
fault.
6E–67
D06RY00159
A sudden clutch