Content .. 394 395 396 397 ..

Chrysler 300M, Dodge Interpid. Manual - part 396

(1) Open hood and disconnect the negative battery

cable remote terminal from the remote battery pos-
t(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/CA-
BLES - REMOVAL).

(2) Remove lower right underpanel silencer/duct.
(3) Disconnect wiring connector to the power mod-

ule.

(4) Remove the power module retaining screws.
(5) Pull the power module out of HVAC housing.

INSTALLATION

(1) Install the power module in the HVAC housing.
(2) Install the two screws that secure the power

module to the HVAC housing and tighten to 2.2 N·m
(20 in. lbs.).

(3) Plug in the harness connector to the power

module.

(4) Install the lower right underpanel silencer/

duct.

(5) Connect the negative battery cable remote ter-

minal to the remote battery post(Refer to 8 - ELEC-
TRICAL/BATTERY

SYSTEM/CABLES

INSTALLATION).

BLOWER MOTOR RESISTOR
BLOCK

DESCRIPTION

Vehicles with manual air conditioning (non-ATC)

systems will have a blower motor resistor block. The
resistor block is mounted to the lower right side of
the HVAC housing in the passenger compartment,
where it can be accessed for service.

The blower motor resistor has multiple resistor

wires, each of which will change the resistance in the
blower motor ground path to change the blower
motor speed. The blower motor switch directs the
ground path through the correct resistor wire to
obtain the selected blower motor speed.

The blower motor resistor cannot be repaired and,

if faulty or damaged, it must be replaced.

OPERATION

With the blower motor switch in the lowest speed

position the ground path for the motor is applied
through all of the resistor wires. Each higher speed
selected with the blower motor switch applies the
blower motor ground path through fewer of the resis-
tor wires, increasing the blower motor speed. When
the blower motor switch is in the highest speed posi-
tion, the blower motor resistor is bypassed and the
blower motor receives a direct path to ground.

DIAGNOSIS AND TESTING - BLOWER MOTOR
RESISTOR BLOCK

For circuit descriptions and diagrams, (Refer to

Appropriate Wiring Information).

WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.

(1) Disconnect and isolate the battery negative

cable.

(2) Unplug the wire harness connector from the

blower motor resistor.

(3) Check for continuity between each of the

blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and the
blower motor resistor or blower motor as required. If
not OK, replace the faulty blower motor resistor.

REMOVAL

(1) Open hood and disconnect the negative battery

cable remote terminal from the remote battery post
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/CA-
BLES - REMOVAL).

(2) Remove lower right underpanel silencer/duct.
(3) Disconnect wiring connector to the blower

motor resistor.

CONTROLS

24 - 15

POWER MODULE (Continued)

(4) Remove the blower motor resistor retaining

screws.

(5) Remove the blower motor resistor from the

HVAC housing.

INSTALLATION

(1) Install the blower motor resistor in the HVAC

housing.

(2) Install the two screws that secure the blower

motor resistor to the HVAC housing and tighten to
2.2 N·m (20 in. lbs.).

(3) Plug in the harness connector to the blower

motor resistor.

(4) Install the lower right underpanel silencer/

duct.

(5) Connect the negative battery cable remote ter-

minal to the remote battery post(Refer to 8 - ELEC-
TRICAL/BATTERY

SYSTEM/CABLES

INSTALLATION).

EVAPORATOR TEMPERATURE
SENSOR

DESCRIPTION

The evaporator temperature sensor is a tempera-

ture sensing element located at the coldest point on
the face of the evaporator. The evaporator tempera-
ture sensor prevents condensate water on the evapo-
rator coil from freezing which can block airflow. The
probe is a thermistor inside a metal tube which is
wedged between the evaporator fins. The metal tube
is tightly held by the evaporator fins so that the ther-
mistor in the tube will detect the temperature of the
evaporator. The thermistor will change resistance as
the temperature changes.

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

t 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. 12) for the correct setpoint.

REMOVAL

(1) Open the hood and disconnect the negative bat-

tery cable remote terminal from the remote battery
post (Refer to 8 - ELECTRICAL/BATTERY SYSTEM/
CABLES - REMOVAL).

(2) Remove the right under panel silencer.
(3) Disconnect the wiring connector for the evapo-

rator probe.

(4) At the center of the HVAC housing, locate the

evaporator probe access plate. Using a flat blade pry
tool, pull back on the locking tab. Twist the access
plate counter clockwise one-quarter turn, and push
the plate inside the HVAC housing (Fig. 13).

(5) Orient the plate in such a way that allows it to

be pulled through the mounting hole, and remove it.

(6) Pull the evaporator probe out of evaporator

core.

INSTALLATION

The new probe must not go into the same

hole (in the evaporator coil) that the old probe
was removed.

(1) The evaporator is manufactured with three

holes for probe insertion. Insert the probe in the
uppermost hole.

(2) Insert the access plate inside the HVAC hous-

ing and orientate it so that the locking tab is one-

Fig. 12 EVAPORATOR TEMPERATURE SENSOR SET

POINT

EVAPORATOR TEMPERATURE SENSOR SET POINT

AMBIENT TEMPERATURE

SENSOR READING °F (° C)

A/C CLUTCH OFF

EVAPORATOR TEMPERATURE

SET POINT ° F (° C)

185 (85)

31 (-0.5)

100 (37.7)

31 (-0.5)

77 (25)

34 (1.1)

60 (15.5)

35 (1.6)

-70 (-56.6)

36 (2.2)

24 - 16

CONTROLS

BLOWER MOTOR RESISTOR BLOCK (Continued)

quarter turn clockwise to where the tab snaps into
the HVAC case detent. Note that the plate will be
flush with the outside of the HVAC housing.

(3) Turn the plate one-quarter turn counter clock-

wise to seat the locking tab in the HVAC case detent.

(4) Connect the wiring harness connector for the

evaporator probe.

(5) Install the right under panel silencer.
(6) Connect the negative battery cable remote ter-

minal to the remote battery post(Refer to 8 - ELEC-
TRICAL/BATTERY

SYSTEM/CABLES

INSTALLATION).

IN-CAR TEMPERATURE
SENSOR

DESCRIPTION

The Automatic Temperature Control (ATC) in-car

temperature sensor returns electrical signals to the
Body Control Module (BCM). The in-car temperature
sensor is used on ATC equipped vehicles only. The in-
car temperature sensor is made up of two parts. One
part is the in-car sensor aspirator motor assembly,
and the second part is a temperature thermistor. The
in-car sensor aspirator motor assembly attaches to
the back of the ATC Control head (Fig. 14). This
assembly has a small fan and a motor which draws
air through the intake on the front of the ATC con-
trol. The in-car sensor thermistor is located inside of
the ATC Control Head. The in-car sensor aspirator
motor is part of the ATC Control and not a separate
serviceable part. The ATC Control must be replaced
if there is a fault relating to the motor. The in-car
temperature sensor thermistor is part of the ATC
Control and not a separate serviceable part. One
must replace the ATC Control if the ATC self-diag-

nostics indicates a fault code. (Refer to 24 - HEAT-
ING & AIR CONDITIONING - DIAGNOSIS AND
TESTING - SELF DIAGNOSTICS)

OPERATION

Air drawn from the passenger compartment by the

in-car sensor aspirator motor assembly, and flows
over the thermistor. The in-car sensor thermistor
changes resistance with air temperature. The BCM
measures this resistance and calculates the tempera-
ture of the air drawn into the ATC Control. The ATC
system then makes adjustments to maintain the opti-
mum passenger compartment comfort. Refer to the
ATC In-Car Sensor Aspirator Motor Operation table
for when the ATC Sensor is operating.

IN-CAR SENSOR ASPIRATOR MOTOR OPERATION

CONDITION

MOTOR OPERATION

IGNITION SWITCH IS
ON

MOTOR ALWAYS
OPERATES, EVEN
WHEN ATC CONTROL
HEAD

OFF

BUTTON IS

PUSHED

VEHICLE IS DRIVEN,
THEN THE IGNITION
SWITCH IS TURNED
OFF

MOTOR TURNS OFF
WHEN THE IGNITION
SWITCH IS TURNED
OFF

VEHICLE DOOR IS
OPENED, AND LEFT
OPEN, WITHOUT
TURNING ON THE
IGNITION SWITCH

MOTOR WILL TURN ON,
AND THEN TURN OFF
APPROXIMATELY 2
MINUTES FROM THE
TIME THE DOOR WAS
OPENED

VEHICLE DOOR IS
OPENED, AND THEN
CLOSED, WITHOUT
TURNING ON THE
IGNITION SWITCH

MOTOR WILL TURN ON,
AND THEN TURN OFF
APPROXIMATELY 2
MINUTES AFTER THE
DOOR WAS CLOSED

Fig. 13 EVAPORATOR PROBE NEEDLE

1 - EVAPORATOR PROBE

Fig. 14 ATC IN-CAR TEMPERATURE SENSOR

1 - ATC IN-CAR TEMPERATURE SENSOR

CONTROLS

24 - 17

EVAPORATOR TEMPERATURE SENSOR (Continued)

DIAGNOSIS AND TESTING - IN-CAR SENSOR
ASPIRATOR MOTOR

(1) Perform air flow test to check the aspirator

motor assembly.

(a) Turn ignition to the ON position and push

the OFF button to stop the ATC system airflow.
This will make it easier to observe paper in step b.

(b) Place a small piece of newspaper in front of

the aspirator motor opening on the ATC control. If
the paper sticks to the opening, the in-car sensor
aspirator motor is operating properly. The piece of
paper should be only large enough to cover the
grille opening (Fig. 15).

(2) Check if the electrical connection and connector

are OK.

REMOVAL

If the ATC in-car temperature sensor (fault 26) is

verified to be bad, or if there is a problem with the
in-car sensor aspirator motor, then the ATC control
must be replaced. (Refer to 24 - HEATING & AIR
CONDITIONING/CONTROLS/A/C

HEATER

CON-

TROL - REMOVAL)

BLEND DOOR ACTUATOR

DESCRIPTION

The blend door actuator is an electric motor which

mechanically positions the blend door. A potentiome-
ter in the actuator allows the BCM (for both manual
and ATC systems) to know the exact position of the
blend door at all times. The blend door actuator is
not serviceable and must be replaced if found to be
defective.

REMOVAL

(1) Open hood and disconnect the negative battery

cable remote terminal from the remote battery post
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/CA-
BLES - REMOVAL).

(2) Remove the left and right underpanel silencer/

ducts.

(3) Remove the two screws from the actuator

which are accessible from the right side of the center
stack (Fig. 16).

(4) Remove one screw from actuator on the left

side.

(5) Pull the actuator straight down from shaft and

disconnect the electrical connection. Upon removal,
note the shaft position of the actuator, because the
shaft on this motor is keyed. When installing a new
actuator, its shaft must be positioned in the same
location.

INSTALLATION

(1) Connect the wire harness connector to the

blend door actuator.

(2) Install the blend door actuator on the HVAC

housing, making sure its keyed shaft is positioned
properly.

(3) Install the three fastener screws and tighten to

2.2 N·m (20 in. lbs.).

(4) Install the left and right underpanel silencer/

ducts.

Fig. 15 ATC IN-CAR TEMPERATURE SENSOR

1 - GRILLE OPENING

24 - 18

CONTROLS

IN-CAR TEMPERATURE SENSOR (Continued)

Content .. 394 395 396 397 ..