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24 - 20
CONTROLS
EVAPORATOR TEMPERATURE SENSOR (Continued)
OPERATION
The Body Control Module (BCM) will send a Pro-
grammable Communications Interface (PCI) bus mes-
sage to the Powertrain Control Module (PCM), which
will check engine, coolant temperature, and refriger-
ant pressure temperature before turning ON the A/C
Compressor Clutch. Turning ON the A/C Compressor
Clutch will allow the system to cool the evaporator.
The BCM will send a message to the PCM when the
evaporator temperature becomes too cold. The PCM
will then turn OFF the A/C Compressor Clutch,
before evaporator freeze up occurs. The DRBIII scan
tool can be used to monitor this operation. The tem-
perature set point at which the clutch is turned OFF
varies with the outside ambient temperature. The
temperature at which the clutch is turned ON is pre-
set to 2° F above the OFF setpoint mentioned above.
Refer to Evaporator Temperature Sensor Set point
table and (Fig. 17) for the correct setpoint.
Fig. 17 EVAPORATOR TEMPERATURE SENSOR SET
EVAPORATOR TEMPERATURE SENSOR SET POINT
AMBIENT TEMPERATURE
SENSOR READING °F (° C)
185 (85)
100 (37.7)
77 (25)
60 (15.5)
-70 (-56.6)
REMOVAL
(1) Disconnect negative battery cable.
(2) Remove the blower motor(Refer to 24 - HEAT-
ING
&
AIR
CONDITIONING/DISTRIBUTION/
BLOWER MOTOR - REMOVAL).
(3) Remove resistor card from underside of HVA-
C(Refer to 24 - HEATING & AIR CONDITIONING/
POINT
A/C CLUTCH OFF
EVAPORATOR TEMPERATURE
SET POINT ° F (° C)
31 (-0.5)
31 (-0.5)
34 (1.1)
35 (1.6)
36 (2.2)
CONTROLS/BLOWER MOTOR RESISTOR BLOCK -
REMOVAL).
(4) Lower the glove box door.
(5) Reach through the glove compartment door
opening and disconnect the evaporator temperature
sensor wiring connector.
(6) Using a flat blade pry tool, pull back on the
locking tab. Twist access plate clockwise one-quarter
turn and pushed inside the A/C housing (Fig. 18).
Then orientated the plate in such a way that it can
be removed from the housing.
Fig. 18 Evaporator Probe
1 - EVAPORATOR PROBE
(7) Using the access plate hole in the housing as a
view hole, reach hand up through blower opening to
pull the evaporator probe from the evaporator coil.
INSTALLATION
(1) Install new sensor into the evaporator.
NOTE: The evaporator is manufactured with three
holes for probe insertion. Insert the probe in the
uppermost hole.
(2) Using the access plate hole in the housing as a
view hole, reach up through blower opening to install
the evaporator probe to the evaporator coil.
(3) Replace access plate to HVAC housing.
(4) Reach through the glove compartment door
opening and connect the evaporator temperature sen-
sor wiring connector.
(5) Install glove compartment door.
(6) Install the resistor card to the underside of the
HVAC(Refer to 24 - HEATING & AIR CONDITION-
ING/CONTROLS/BLOWER
BLOCK - INSTALLATION).
(7) Install the blower motor(Refer to 24 - HEAT-
ING
&
AIR
CONDITIONING/DISTRIBUTION/
BLOWER MOTOR - INSTALLATION).
(8) Connect negative battery cable.
JR
MOTOR
RESISTOR
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