Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 509

INSTALLATION

(1) Install the rear A/C blower motor switch into

the accessory switch panel. Make sure the retaining
tabs are fully engaged.

(2) Connect the wire harness connector to the rear

A/C blower motor switch.

(3) Install the accessory switch panel (Refer to 23 -

BODY/INSTRUMENT

PANEL/ACCESSORY

SWITCH BEZEL - INSTALLATION).

(4) Reconnect the negative battery cable.

EVAPORATOR TEMPERATURE
SENSOR

DESCRIPTION

The rear evaporator temperature sensor (Fig. 15) is

used to signal the rear A/C control module to cycle
the rear A/C clutch in order to control rear evapora-
tor temperature. Controlling the evaporator tempera-
ture prevents condensation on the evaporator fins
from freezing and obstructing rear A/C system air
flow.

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.

The rear evaporator temperature sensor is located

in the rear A/C evaporator housing.

OPERATION

The rear evaporator temperature sensor signals

the rear A/C control module to cycle the rear A/C
clutch off if the rear evaporator temperature goes
below approximately 1.6° C (35° F). When the tem-
perature reaches above approximately 3.9° C (39° F),
the rear evaporator temperature sensor signals the
rear A/C control module to cycle the rear A/C clutch
back on.

The rear evaporator temperature sensor cannot be

adjusted or repaired. If faulty or damaged, it must be
replaced. Refer to the appropriate wiring information
for complete HVAC wiring diagrams.

REMOVAL

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the air filter from the rear A/C evapo-

rator housing (Refer to 24 - HEATING & AIR CON-
DITIONING/DISTRIBUTION - REAR/AIR FILTER -
REMOVAL).

(3) Reach up into the rear A/C evaporator housing

and disconnect the two wire harness connectors from
the rear evaporator temperature sensor (Fig. 16).

(4) Carefully remove the sensor probe from the

rear A/C evaporator.

(5) Remove the two screws that secure the rear

evaporator sensor to the rear A/C evaporator housing
and remove the sensor.

Fig. 14 Rear A/C Blower Motor Switch

1 - WIRE HARNESS CONNECTOR
2 - REAR A/C BLOWER MOTOR SWITCH
3 - ACCESSORY SWITCH PANEL

Fig. 15 Rear Evaporator Temperature Sensor

1 - SWITCH UNIT
2 - MOUNTING TAB (2)
3 - CAPILLARY TUBE
4 - WIRE CONNECTORS

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CONTROLS - REAR

24 - 37

INSTALLATION

(1) Position the rear evaporator temperature sen-

sor to the rear A/C evaporator housing.

(2) Install the two screws that secure the rear

evaporator temperature sensor to the rear A/C evap-
orator housing. Tighten the screws to 2 N·m (17 in.
lbs.).

(3) Install the sensor probe into the rear A/C evap-

orator.

(4) Connect the two wire harness connectors to the

rear evaporator temperature sensor.

(5) Install the rear air filter (Refer to 24 - HEAT-

ING

&

AIR

CONDITIONING/DISTRIBUTION

-

REAR/AIR FILTER - INSTALLATION).

(6) Reconnect the negative battery cable.

TEMPERATURE CONTROL

DESCRIPTION

The temperature control for the optional rear A/C

system is a thumbwheel-type control mounted in the
switch panel on the instrument panel (Fig. 17). The
rear A/C temperature control allows the selection of
four temperature settings when the rear A/C blower
motor is activated.

OPERATION

With the front A/C switch and rear blower motor

activated, the rear A/C output temperature can be
selected by rotating the thumbwheel control upwards
(increase cooling) or downwards (decrease cooling).
Depending on the rear A/C temperature control posi-
tion, a temperature command signal is sent to the

Fig. 16 Rear Evaporator Temperature Sensor

1 - REAR A/C EVAPORATOR HOUSING
2 - SCREWS (2)
3 - REAR EVAPORATOR SENSOR SWITCH UNIT

4 - WIRE HARNESS CONNECTORS
5 - REAR EVAPORATOR SENSOR PROBE

Fig. 17 Rear A/C Temperature Control

24 - 38

CONTROLS - REAR

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rear A/C control module. The temperature of the cir-
culated internal air of the rear compartment is mea-
sured by a temperature sensor located in the rear
evaporator unit. The value of the temperature sensor
is compared in the rear A/C control module with an
adjusted value at the rear A/C temperature control.

The rear A/C temperature control cannot be

repaired and, if faulty or damaged, it must be
replaced.

DIAGNOSIS AND TESTING

REAR A / C TEMPERATURE CONTROL

Before testing the rear A/C temperature control,

verify that the front A/C system is operating correctly
by performing the ATC Function Test using the
DRBIII

t scan tool. Use a volt/ohmmeter to test the

control. For circuit descriptions and diagrams, refer
to the appropriate wiring information. The wiring
information includes wiring diagrams, proper wire
and connector repair procedures, details of wire har-
ness routing and retention, connector pin-out infor-
mation and location views for the various wire
harness connectors, splices and grounds.

WARNING: To avoid personal injury or death, on
vehicles equipped with airbags, disable the supple-
mental

restraint

system

before

attempting

any

steering wheel, steering column, airbag, seat belt
tensioner, impact sensor, or instrument panel com-
ponent diagnosis or service. Disconnect and isolate
the battery negative (ground) cable, then wait two
minutes for the system capacitor to discharge
before performing further diagnosis or service. This
is the only sure way to disable the supplemental
restraint system. Failure to take the proper precau-
tions could result in accidental airbag deployment.

(1) Disconnect and isolate the battery negative

cable.

(2) Unplug the wire harness connector from the

rear A/C temperature control.

(3) Check for continuity between terminal 9 and

terminals 3 and 5 of the A/C temperature control. In
all instances, there should be continuity.

NOTE: To check the switch’s internal circuits, con-
nect the positive lead of the ohmmeter to terminal 9
and the negative lead to terminals 3 and 5. To
check the switches integral light emitting diode,
reverse the ohmmeter leads.

(4) Check for resistance between terminal 3 and 5

of the A/C temperature control as you move the con-
trol to each temperature position. Resistance should
be present and should change for each position.

(5) If OK, test and repair the rear A/C tempera-

ture control wire harness circuits. If not OK, replace
the faulty rear A/C temperature control.

REMOVAL

WARNING: To avoid personal injury or death, on
vehicles equipped with airbags, disable the supple-
mental

restraint

system

before

attempting

any

steering wheel, steering column, airbag, seat belt
tensioner, impact sensor, or instrument panel com-
ponent diagnosis or service. Disconnect and isolate
the battery negative (ground) cable, then wait two
minutes for the system capacitor to discharge
before performing further diagnosis or service. This
is the only sure way to disable the supplemental
restraint system. Failure to take the proper precau-
tions could result in accidental airbag deployment.

NOTE: The rear A/C temperature control is used
only on models with the optional rear A/C unit.

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the accessory switch panel from the

instrument panel (Refer to 23 - BODY/INSTRU-
MENT

PANEL/ACCESSORY

SWITCH

BEZEL

-

REMOVAL).

(3) Disconnect the wire harness connector from the

rear A/C temperature control (Fig. 18).

(4) Disengage the retaining tabs and remove the

rear A/C temperature control from the accessory
switch panel.

Fig. 18 Rear A/C Temperature Control

1 - WIRE HARNESS CONNECTOR
2 - REAR A/C TEMPERATURE CONTROL
3 - ACCESSORY SWITCH PANEL

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CONTROLS - REAR

24 - 39

INSTALLATION

(1) Install the rear A/C temperature control into

the accessory switch panel. Make sure the retaining
tabs are fully engaged.

(2) Connect the wire harness connector to the rear

A/C temperature control.

(3) Install the accessory switch panel (Refer to 23 -

BODY/INSTRUMENT

PANEL/ACCESSORY

SWITCH BEZEL - INSTALLATION).

(4) Reconnect the negative battery cable.

TEMPERATURE SENSOR

DESCRIPTION

The rear temperature sensor (Fig. 19) provides an

air outlet temperature signal to the rear A/C control
module through a two-wire harness lead and connec-
tor.

The rear temperature sensor is located in the rear

A/C evaporator housing.

OPERATION

The rear A/C temperature sensor is a variable

resistor that operates on a five-volt reference signal
sent to it by the rear A/C control module. The resis-
tance in the sensor changes as air temperature
changes. Based upon the resistance in the sensor, a
specific voltage on the temperature sensor signal cir-
cuit is returned to the rear A/C control module,
which is programmed to correspond to a specific tem-
perature.

The

rear A/C

temperature

sensor

cannot

be

adjusted or repaired and, if faulty or damaged, it
must be replaced.

DIAGNOSIS AND TESTING

REAR TEMPERATURE SENSOR

(1) Disconnect and isolate the negative battery

cable.

(2) Disconnect the wire harness connector from the

rear temperature sensor.

(3) Measure the resistance of the rear temperature

sensor. At –40° C (–40° F), the sensor resistance
should be approximatley 336 kilohms. At 55° C (131°
F), the sensor resistance is should be approximaytly
25 kilohms. The rear sensor resistance should read
between these two values.

(4) If OK, test and repair the rear temperature

sensor wire harness circuits. Refer to the appropriate
wiring information for rear temperature sensor cir-
cuit descriptions and for complete HVAC wiring dia-
grams. If not OK, replace the faulty temperature
sensor (Refer to 24 - HEATING & AIR CONDITION-
ING/CONTROLS - REAR/TEMPERATURE SENSOR
- REMOVAL).

REMOVAL

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the air filter from the rear A/C evapo-

rator housing (Refer to 24 - HEATING & AIR CON-
DITIONING/DISTRIBUTION - REAR/AIR FILTER -
REMOVAL).

(3) Reach up into the rear A/C evaporator housing

and disconnect the wire harness connector from the
rear temperature sensor (Fig. 20).

(4) Carefully remove the rear temperature sensor

from the bracket.

Fig. 19 Rear Temperature Sensor

1 - REAR TEMPERATURE SENSOR
2 - WIRE HARNESS CONNECTOR

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CONTROLS - REAR

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