Mercedes-Benz Sprinter / Dodge Sprinter. Manual - part 508

INSTALLATION

NOTE: Replacement of the PTFE thread sealing
tape is required anytime the rear A/C low pressure
switch is removed from the rear suction line line.
Failure to replace the sealing tape could result in a
rear refrigerant system leak.

(1) Remove the tape or plug from the rear suction

line fitting.

(2) Install PTFE thread sealing tape onto the rear

A/C low pressure switch and install the switch onto
the rear suction line. Tightened the A/C low pressure
switch to 10 N·m (88 in. lbs.).

(3) Connect the wiring harness connector to the

rear A/C low pressure switch.

(4) Install new insulating tape around the rear A/C

low pressure switch area.

(5) Reconnect the negative battery cable.
(6) Evacuate the rear refrigerant system (Refer to

24 - HEATING & AIR CONDITIONING/PLUMBING
- STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE).

(7) Charge the rear refrigerant system (Refer to 24

- HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE).

(8) Install the cover onto the rear A/C evaporator

housing (Refer to 24 - HEATING & AIR CONDI-
TIONING/DISTRIBUTION - REAR/A/C EVAPORA-
TOR COVER-REAR - INSTALLATION).

BLOWER MOTOR RELAY

DESCRIPTION

The three rear blower motor relays used for the

rear A/C system are International Standards Organi-
zation (ISO)-type relays (Fig. 11). Relays conforming
to the ISO specifications have common physical
dimensions, current capacities, terminal functions
and patterns. The rear blower motor relays are elec-
tromechanical devices that switches fused battery
current directly to the rear blower motors. The rear
blower motor relays are energized when the relay
coils are provided battery current by the rear blower
motor switch (Refer to 24 - HEATING & AIR CON-
DITIONING/CONTROLS/BLOWER

MOTOR

SWITCH - DESCRIPTION).

The rear blower motor relays are located in the

relay block in the rear A/C evaporator housing.

OPERATION

The three ISO-standard rear blower motor relays

are electromechanical switches that uses a low cur-
rent input from the rear blower motor switch to con-
trol the high current output to the rear blower
motors. The movable, common feed relay contact is
held against the fixed, normally closed relay contact
by spring pressure. When the electromagnetic relay
coil is energized, it draws the movable common feed
relay contact away from the fixed, normally closed
relay contact and, holds it against the fixed, normally
open relay contact. This action allows high current to
flow to the rear blower motors.

When the relay coil is de-energized, spring pres-

sure returns the movable relay contact back against
the fixed, normally closed contact point. The resistor

Fig. 10 Rear A/C Low Pressure Switch

1 - INSULATING TAPE
2 - REAR A/C EVAPORATOR HOUSING
3 - WIRE HARNESS CONNECTOR
4 - REAR A/C LOW PRESSURE SWITCH
5 - REAR SUCTION LINE FITTING

Fig. 11 Rear Blower Motor Relays

1 - STANDARD ISO RELAY
2 - TERMINAL PATTERN

CONTROLS - REAR

24 - 33

or diode is connected in parallel with the relay coil,
and helps to dissipate voltage spikes and electromag-
netic interference that can be generated as the elec-
tromagnetic field of the relay coil collapses.

The rear blower motor relay terminals are con-

nected to the vehicle electrical system through recep-
tacles in the relay block located in the rear A/C
evaporator housing.

The rear blower motor relays cannot be repaired

and, if faulty or damaged, they must be replaced.
Refer to the appropriate wiring information for diag-
nosis and testing of the ISO-standard relay and 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 remove the rear blower motor relays as neces-
sary from the relay block (Fig. 12).

24 - 34

CONTROLS - REAR

INSTALLATION

(1) Position the rear blower motor relays into the

proper receptacle of the relay block located in the
rear A/C evaporator housing as necessary.

(2) Align the blower motor relay terminals with

the terminal cavities in the relay block receptacle
and push down firmly on the relay until the termi-
nals are fully seated.

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

ING

AIR

CONDITIONING/DISTRIBUTION

REAR/AIR FILTER - INSTALLATION).

(4) Reconnect the negative battery cable.

BLOWER MOTOR SWITCH

DESCRIPTION

The blower motor for the optional rear A/C system

is controlled by a three position rocker switch
mounted in the switch panel located on the instru-
ment panel (Fig. 13). The rear A/C blower motor
switch allows the selection of one of two blower
motor speeds and an Off position.

OPERATION

With the front A/C switch activated, the rear

blower motor speed can be selected by pressing the
rocker switch upwards (high speed) or downwards
(low speed). To turn the rear blower motor off, switch
the blower motor switch to the center position.
Depending on the blower motor switch position, a
blower motor speed command signal is sent to one of
the two blower motor relays. When activated, relay 1
sends power through an integral resistor within the
rear A/C control module and then to the blower

Fig. 12 Rear Blower Motor Relays

1 - REAR A/C EVAPORATOR HOUSING
2 - BLOWER MOTOR RELAY K204
3 - BLOWER MOTOR RELAY K203

4 - BLOWER MOTOR RELAY K201
5 - REAR CONDENSER FAN RELAY K205
6 - REAR COMPRESSOR RELAY K206

Fig. 13 Rear Air Conditioning Switch

CONTROLS - REAR

24 - 35

motor, while relay 2 when activated, sends power
directly to the blower motor.

The rear blower motor switch cannot be repaired

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

DIAGNOSIS AND TESTING

REAR BLOWER MOTOR SWITCH

Before testing the rear blower motor switch, verify

that the front A/C system is functional by performing
the ATC Fuction Test using the DRBIII

t scan tool.

Use a volt/ohmmeter to test the rear blower motor
switch. 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 blower motor switch.

(3) Check for continuity between terminal 10 and

terminals 1, 7 and 4 of the blower motor switch. In
all instances, there should be continuity.

NOTE: To check the switch’s internal circuits, con-
nect the negative lead of the ohmmeter to terminal
10 and the positive ohmmeter lead to terminals 1, 7
and 4. To check the switch’s integral light emitting
diodes, reverse the ohmmeter leads.

(4) Check for continuity between the rear blower

motor switch terminals 3 and 7 as you move the
blower motor switch to each of the two speed posi-
tions, and the Off position. There should be continu-
ity in only one blower motor switch speed position.

(5) Check for continuity between the rear blower

motor switch terminals 4 and 8 as you move the
blower motor switch to each of the two speed posi-
tions, and the Off position. There should be continu-

ity in only the other blower motor switch speed
position.

(6) If OK, test and repair the rear blower motor

switch wire harness circuits. If not OK, replace the
faulty rear blower motor switch.

REMOVAL

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

restraint

system

before

attempting

any

NOTE: The rear A/C blower motor switch is used on
vehicles with the optional rear A/C system.

(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 blower motor switch (Fig. 14).

(4) Disengage the retaining tabs and remove the

rear A/C blower motor switch from the accessory
switch panel.

24 - 36

CONTROLS - REAR

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