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24 - 26
CONTROLS - REAR
EVAPORATOR TEMPERATURE SENSOR (Continued)
The rear evaporator temperature sensor consists of
a probe and a switch unit. The probe, which is a Neg-
ative Temperature Coefficient (NTC) thermistor in a
capillary tube, is inserted between the rear evapora-
tor coil fins to monitor evaporator temperature. The
switch unit contains internal control logic that mon-
itors the input from the probe in order to switch an
internal transistor that controls the output signal to
the rear A/C control module.
OPERATION
When the rear evaporator temperature sensor sees
a temperature input below about 1.6° C (35° F), it
signals the rear A/C control module to cycle the rear
A/C solenoid valve closed. When the temperature
input reaches above about 3.9° C (39° F), the switch
signals the control module to cycle the valve open.
The rear evaporator temperature sensor can be
accessed for service by removing the air inlet grate
from the rear evaporator housing. The rear evapora-
tor temperature sensor cannot be adjusted or
repaired. If faulty or damaged, the sensor must be
replaced.
DIAGNOSIS AND TESTING
Before testing the rear evaporator temperature
sensor, verify that the front A/C system is operating
correctly by performing the ATC Function Test using
the DRBIII scan tool. Use a volt/ohmmeter to test
the sensor. For circuit descriptions and diagrams,
refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, details of wire
harness routing and retention, connector pin-out
information and location views for the various wire
harness connectors, splices and grounds.
(1) Turn the ignition switch and the front A/C
switch to the On position. Place the rear blower
motor switch in either low or high speed position.
Check for voltage to the rear evaporator relay from
the rear evaporator temperature sensor. If OK, go to
Step 2. If not OK, repair the open or shorted evapo-
rator temperature sensor circuit as required.
(2) With the ambient temperature between 20 to
30° C (68 to 90° F), start the engine and run the rear
air conditioning system. The rear A/C solenoid valve
should cycle open and closed. Use a voltmeter con-
nected to the output side of the sensor for this check.
If the A/C solenoid valve fails to cycle in these tem-
peratures, replace the faulty rear evaporator temper-
ature sensor.
NOTE: If the ambient temperature is above 32° C
(90° F) the rear A/C solenoid valve may not cycle
due to the high heat load. This condition is normal.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the air inlet grate from the rear evap-
orator housing (Fig. 6).
(3) Disconnect the two wire harness connectors
from the rear evaporator temperature sensor.
(4) Remove the sensor probe from the rear evapo-
rator.
(5) Remove the two sensor retaining screws and
remove the sensor from the vehicle.
Fig. 6 Rear Evaporator Temperature Sensor
1 - RUBBER GROMMET
2 - WIRE HARNESS CONNECTOR (2)
3 - REAR EVAPORATOR TEMPERATURE SENSOR
4 - SCREW (2)
5 - TEMPERATURE SENSOR PROBE
6 - AIR INLET GRATE
INSTALLATION
(1) Install the rear evaporator temperature sensor
and the two sensor retaining screws. Tighten the
screws to 2 N·m (17 in. lbs.).
(2) Install the sensor probe into the rear evapora-
tor.
(3) Connect the two wire harness connectors to the
rear evaporator temperature sensor.
(4) Install the air inlet grate onto the rear evapo-
rator housing.
(5) Reconnect the battery negative cable.
VA
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