Dodge Viper SRT-10 (ZB). Manual — part 261

110 kPa (16 psi) and will re-engage the clutch when
the high side pressure rises above 220 kPa (32 psi).
If the refrigerant pressure rises above 1654 kPa (240
psi), the PCM will actuate the cooling fan. The A/C
pressure transducer input to the PCM will also pre-
vent the A/C compressor clutch from engaging when
ambient temperatures are below about 1.0° C (50° F)
due to the pressure/temperature relationship of the
refrigerant.

The A/C pressure transducer is diagnosed using a

DRBIII

t scan tool. Refer to the appropriate diagnos-

tic information.

The A/C pressure transducer cannot be adjusted or

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

DIAGNOSIS AND TESTING

A/C PRESSURE TRANSDUCER

The A/C pressure transducer is tested using a

DRBIII

t scan tool. Refer to the appropriate diagnos-

tic information. Before testing the A/C pressure
transducer, be certain that the transducer wire har-
ness connection is clean of corrosion and properly
connected. For the A/C to operate, an A/C pressure
transducer voltage reading between 0.451 and 4.519
volts is required. Voltages outside this range indicate
a low or high refrigerant system pressure condition
to the powertrain control module (PCM). The PCM is
programmed to respond to a low or high refrigerant
system pressure by suppressing operation of the A/C
compressor. Refer to the A/C Pressure Transducer
Voltage chart for the possible conditions indicated by
the transducer voltage reading.

A/C PRESSURE TRANSDUCER VOLTAGE

Voltage

Possible Indication

0.0

1. No sensor supply voltage
from PCM.

2. Shorted sensor circuit.

3. Faulty transducer.

0.150 TO 0.450

1. Ambient temperature below
10° C (50° F).

2. Low refrigerant system pres-
sure.

0.451 TO 4.519

1. Normal refrigerant system
pressure.

4.520 TO 4.850

1. High refrigerant system pres-
sure.

5.0

1. Open sensor circuit.

2. Faulty transducer.

REMOVAL

NOTE: Note: It is not necessary to discharge the
refrigerant system to replace the A/C pressure
transducer.

(1) Disconnect and isolate the negative battery cable.
(2) Disconnect the wire harness connector from the

A/C pressure transducer (Fig. 14)

(3) Remove the A/C pressure transducer from the

fitting on the discharge line and remove and discard
the O-ring seal.

INSTALLATION

NOTE: Use only the specified O-ring as it is made
of special material for R-134a. Use only refrigerant
oil of the type required for the A/C compressor.

(1) Lubricate a new rubber O-ring seal with clean

refrigerant oil and install it on the A/C pressure
transducer fitting.

(2) Install the A/C pressure transducer onto the

discharge line. Tighten the A/C pressure transducer
securely.

(3) Connect the wire harness connector to the A/C

pressure transducer.

(4) Reconnect the negative battery cable.

Fig. 14 A/C Pressure Transducer

1 - DISCHARGE LINE
2 - SCREW
3 - A/C PRESSURE TRANSDUCER
4 - RADIATOR/FAN/CONDENSER MODULE
5 - WIRE HARNESS CONNECTOR
6 - LH FRAME RAIL

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A/C PRESSURE TRANSDUCER (Continued)

BLEND DOOR ACTUATOR

DESCRIPTION

The blend door actuator is a reversible, 12-volt

direct current (DC), servo motor which mechanically
positions the blend-air door. The blend door actuator
is located on the top of the HVAC housing.

The blend door actuator is contained within a

black molded plastic housing with an integral wire
connector receptacle and three integral mounting
tabs that allow the actuator to be secured with three
screws to the HVAC housing. The blend door actuator
also has an output shaft with splines that connects it
to the linkage that drives the blend-air door. The
blend door actuator does require mechanical indexing
to the blend door linkage, as it is electronically cali-
brated by the A/C-heater control.

OPERATION

The blend door actuator is connected to the A/C-

heater control through the vehicle electrical system
by a dedicated two-wire take out and connector of the
HVAC wire harness. The blend door actuator can
move the blend-air door in two directions. When the
A/C-heater control pulls the voltage on one side of
the motor connection high and the other connection
low, the blend-air door will move in one direction.
When the A/C-heater control reverses the polarity of
the voltage to the motor, the blend-air door moves in
the opposite direction. When the A/C-heater control
makes the voltage to both connections high or both
connections low, the blend-air door stops and will not
move. The motor connections also provide a feedback
signal to the A/C-heater control. This feedback signal
allows the A/C-heater control to monitor the opera-
tion and relative position of the blend door actuator
and the blend-air door. The A/C-heater control learns
the blend-air door stop positions during the calibra-
tion procedure and will store a diagnostic trouble
code (DTC) for any problems it detects in the blend
door actuator circuit.

NOTE: If battery voltage is low or not sensed at the
blend door actuator for less than a 60 second inter-
val, the blend door actuator will be out of calibra-
tion. Remove fuse #3 BCM1 (I.O.D. fuse) for a
minimum of 60 seconds. The blend door actuator
will then self calibrate upon reinstallation of the
fuse.

The blend door actuator can be diagnosed using a

DRBIII

t scan tool. Refer to Body Diagnostic Proce-

dures for more information.

The blend door actuator cannot be adjusted or

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

REMOVAL

WARNING: On vehicles equipped with airbags, dis-
able the airbag system before attempting any steer-
ing wheel, steering column, or instrument panel
component diagnosis or service. Disconnect and
isolate the battery negative (ground) cable, then
wait two minutes for the airbag system capacitor to
discharge before performing further diagnosis or
service. This is the only sure way to disable the air-
bag system. Failure to take the proper precautions
could result in accidental airbag deployment and
possible personal injury or death.

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the instrument panel (Refer to 23 -

BODY/INSTRUMENT

PANEL/INSTRUMENT

PANEL ASSEMBLY - REMOVAL).

(3) Disconnect the wire harness connector from the

blend door actuator (Fig. 15).

(4) Remove the three screws that secure the blend

door actuator to the HVAC housing and remove the
actuator.

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CONTROLS

24 - 19

INSTALLATION

(1) Position the blend door actuator to the top of

the HVAC housing. If necessary, rotate the actuator
slightly to align the splines on the actuator output
shaft with those in the blend door pivot shaft.

(2) Install the three screws that secure the blend

door actuator to the HVAC housing. Tighten the
screws to 2 N·m (17 in. lbs.).

(3) Connect the wire harness connector to the

blend door actuator.

(4) Install the instrument panel (Refer to 23 -

BODY/INSTRUMENT

PANEL/INSTRUMENT

PANEL ASSEMBLY - INSTALLATION).

(5) Reconnect the negative battery cable.

BLOWER MOTOR RELAY

DESCRIPTION

The blower motor relay (Fig. 16) is a International

Standards Organization (ISO)-type relay. Relays con-
forming to the ISO specifications have common phys-
ical

dimensions,

current

capacities,

terminal

functions and patterns. The blower motor relay is a
electromechanical device that switches battery cur-
rent from a fuse in the power distribution center
(PDC) directly to the blower motor. The blower motor
relay is energized when the relay coil is provided a
voltage signal by the ignition switch.

The blower motor relay is located in the PDC in

the engine compartment.

OPERATION

The The ISO-standard blower motor relay is an

electromechanical switch that uses a low current
input from the ignition switch to control the high
current output to the blower motor. 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 con-
tact. This action allows high current to flow to the
blower motor.

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
or diode is connected in parallel with the relay coil,
and helps to dissipate voltage spikes and electromag-

Fig. 15 HVAC Housing

1 - RECIRCULATION DOOR ACTUATOR
2 - RECIRCULATION-AIR DOOR
3 - HVAC HOUSING
4 - WIRE HARNESS CONNECTOR
5 - BLEND DOOR ACTUATOR
6 - WIRE HARNESS CONNECTOR
7 - FLOOR/DEFROST MODE DOOR ACTUATOR
8 - PANEL MODE DOOR ACTUATOR
9 - WIRE HARNESS CONNECTOR
10 - HVAC HOUSING MOUNTING BRACKET
11 - EVAPORATOR DRAIN TUBE
12 - HEATER CORE
13 - BLOWER MOTOR
14 - A/C EVAPORATOR
15 - HVAC HOUSING MOUNTING STUD
16 - HVAC HOUSING MOUNTING STUD

Fig. 16 Blower Motor Relay

30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED

24 - 20

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BLEND DOOR ACTUATOR (Continued)

netic interference that can be generated as the elec-
tromagnetic field of the relay coil collapses.

The blower motor relay terminals are connected to

the vehicle electrical system through a receptacle in
the power distribution center (PDC). The inputs and
outputs of the blower motor relay include:

• The common feed terminal (30) receives a bat-

tery current input from a fuse in the PDC through a
fused B(+) circuit at all times.

• The coil ground terminal (85) is connected to a

ground at all times.

• The coil battery terminal (86) receives a battery

current input from a fuse in the junction block (JB)
through a fused ignition switch output (run) circuit
only when the ignition switch is in the On position.

• The normally open terminal (87) provides a bat-

tery current output to the blower motor through the
blower motor relay output circuit only when the
blower motor relay coil is energized.

• The normally closed terminal (87A) is not con-

nected to any circuit in this application, but provides
a battery current output only when the blower motor
relay coil is de-energized.

The blower motor relay cannot be repaired and, if

faulty or damaged, it must be replaced. Refer to the
appropriate wiring information for diagnosis and
testing of the ISO-standard relay and for complete
HVAC wiring diagrams.

REMOVAL

(1) Disconnect and isolate the negative battery

cable.

(2) Open the cover of the power distribution center

(PDC) located in the engine compartment (Fig. 17).

NOTE: Refer to the fuse and relay layout map on
the PDC cover for blower motor relay location.

(3) Remove the blower motor relay from the PDC.

INSTALLATION

NOTE: Refer to the fuse and relay map on the cover
of the power distribution center (PDC) for blower
motor relay location.

(1) Position the blower motor relay into the proper

receptacle of the PDC.

(2) Align the blower motor relay terminals with

the terminal cavities in the PDC receptacle and push
down firmly on the relay until the terminals are fully
seated.

(3) Close the cover of the PDC.
(4) Reconnect the negative battery cable.

BLOWER MOTOR RESISTOR
BLOCK

DESCRIPTION

The blower motor resistor (Fig. 18) is mounted to

the bottom of the HVAC housing, near the blower
motor. The blower motor resistor consists of a molded
plastic mounting plate with an integral wire connec-
tor receptacle. Concealed behind the mounting plate
are coiled resistor wires contained within a ceramic
heat sink.

The blower motor resistor is accessed for service

from under the instrument panel.

OPERATION

The blower motor resistor is connected to the vehi-

cle electrical system through a dedicated wire lead
and connector of the HVAC wire harness. The blower
motor resistor has multiple resistor wires, each of
which will reduce the current flow through the
blower motor to change the blower motor speed.

The blower motor control in the MTC heating-A/C

system directs the ground path for the blower motor
through the correct resistor wire to obtain the
selected speed. With the blower motor control in the
lowest speed position, the ground path for the blower
motor is applied through all of the resistor wires.
Each higher speed selected with the blower motor
control

applies

the

blower

motor

ground

path

through fewer of the resistor wires, increasing the

Fig. 17 Blower Motor Relay

1 - POWER DISTRIBUTION CENTER (PDC)
2 - BRAKE MASTER CYLINDER RESERVOIR

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CONTROLS

24 - 21

BLOWER MOTOR RELAY (Continued)