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JX
DESCRIPTION AND OPERATION
A/C EVAPORATOR TEMPERATURE SENSOR . . . 5
A/C OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . 5
A/C PRESSURE TRANSDUCER . . . . . . . . . . . . . . 6
A/C-HEATER CONTROL . . . . . . . . . . . . . . . . . . . . 5
DESCRIPTION AND OPERATION
A/C-HEATER CONTROL
The air conditioning-heater system is controlled by
the Body Control Module (BCM). The BCM senses
voltage of the A/C-Heater control on circuit C58. The
control uses resistors to internal to the control. These
resistors are connected to the Z2 ground circuit.
When the operator requests a function in the sys-
tem the BCM measures the voltage, on circuit C58,
and activates the mode actuator door to the proper
position.
A separate A/C switch is used in the system. This
switch works the same as the mode actuator
switches. When the operator presses the switch the
BCM measures the voltage on the C21 circuit and
activates the proper functions. Internal to the A/C-
Heater control the A/C switch is connected to the
blower motor switch. This allows the A/C system to
only operate when the blower switch in an ON posi-
tion.
Ground for the A/C switch is provided through the
blower motor switch to the Z1 circuit. This circuit
terminates at the instrument panel ground. A Light
Emitting Diode (LED) is connected in the C21 circuit
and illuminates when the A/C system is operating.
Illumination lamps and LED's are internal to the
control. These are controlled by the BCM. The E2 cir-
cuit from the BCM provides the voltage to the control
for lamp and LED illumination. Ground for the
lamps and LED's is provided on the Z1 circuit which
terminates at the instrument panel left side cowl.
MODE DOOR ACTUATOR (MANUAL A/C)
The mode door actuator is located on the lower left
side of the A/C- Heater housing. This actuator con-
trols the position of the panel/bi-level door and the
floor/defrost door.
Power for the mode door actuator is provided by
the Body Control Module (BCM) on the C26 circuit.
This is a 5 volt feed.
Circuit C35 is the mode drive circuit from the BCM
to the actuator.
8W - 42 AIR CONDITIONING-HEATER
8W-42 AIR CONDITIONING-HEATER
page
INDEX
BLOWER MOTOR OPERATION . . . . . . . . . . . . . . 6
HELPFUL INFORMATION . . . . . . . . . . . . . . . . . . . 6
MODE DOOR ACTUATOR (MANUAL A/C) . . . . . . 5
RADIATOR FAN OPERATION . . . . . . . . . . . . . . . . 6
The C37 circuit is the feedback from the actuator
to the BCM. The BCM uses this information to
adjust the door to the proper position.
Circuit C57 is the sensor return to the BCM. This
circuit is spliced with the blend air door actuator.
Circuit C34 is the common line that is spliced, and
connects, to the blend air door actuator and the recir-
culation door actuator.
A/C EVAPORATOR TEMPERATURE SENSOR
The A/C evaporator temperature sensor, located in
the A/C-Heater housing, provides the Body Control
Module (BCM) with the evaporator temperature to
prevent the evaporator from freezing. Power for the
sensor is provided from the BCM to the sensor on cir-
cuit C12. The ground for the sensor is on circuit C57
to the BCM.
Information on evaporator temperature is sent to
the Powertrain Control Module (PCM) across the
CCD Bus. The PCM uses this information to control
operation of the A/C compressor clutch.
A/C OPERATION
When the A/C switch is CLOSED or the Defrost
switch is moved to the ON position, and the evapora-
tor temperature is in the normal limits, the Body
Control Module (BCM) sends a signal to the Power-
train Control Module (PCM), over the CCD Bus,
requesting A/C operation.
After receiving this input, the PCM activates the
A/C compressor by grounding the C28 circuit, which
is attached to the coil side of the A/C clutch relay.
This relay is located in the Power Distribution Cen-
ter (PDC). Power for the coil side of the relay is sup-
plied on the F18 circuit. The F18 circuit is protected
by a 10 amp fuse located in cavity 9 of the Power
Distribution Center (PDC).
When the coil is energized contacts in the relay
CLOSE connecting circuits A16 and C3. Circuit A16
is protected by a 40 amp fuse located in cavity 17 of
the PDC and also supplies power for the radiator fan
relays. The C3 circuit connects from the relay to the
A/C compressor clutch.
8W - 42 - 5
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