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Dodge Durango (DN). Manual - part 186

UNDERBODY REFRIGERANT LINE. . . . . . . . . . . 69
VACUUM CHECK VALVE . . . . . . . . . . . . . . . . . . . 70
VACUUM RESERVOIR . . . . . . . . . . . . . . . . . . . . 70

ADJUSTMENTS

TEMPERATURE CONTROL CABLE . . . . . . . . . . . 72

SPECIFICATIONS

A/C APPLICATION TABLE . . . . . . . . . . . . . . . . . . 73

DESCRIPTION AND OPERATION

BLOWER MOTOR

FRONT

DESCRIPTION

The blower motor and blower wheel are located in

the passenger side end of the heater-A/C housing,
below the glove box. The blower motor controls the
velocity of air flowing through the heater-A/C hous-
ing by spinning a squirrel cage-type blower wheel
within the housing at the selected speed. The blower
motor and blower wheel can only be serviced with
the heater-A/C housing removed from the passenger
compartment.

OPERATION

The blower motor will only operate when the igni-

tion switch is in the On position, and the heater-A/C
mode control switch knob is in any position, except
Off. The blower motor receives a fused battery feed
through the blower motor relay (Voltage Reduction
Relay or VRR) whenever the ignition switch is in the
On position.

The blower motor battery feed circuit is protected

by a fuse in the Power Distribution Center (PDC).
The blower motor relay control circuit is protected by
a fuse in the junction block. Blower motor speed is
controlled by regulating the ground path through the
heater-A/C mode control switch, the blower motor
switch, the blower motor resistor, the blower motor
relay (VRR), and the high speed blower motor relay.

The blower motor and blower motor wheel cannot

be repaired and, if faulty or damaged, they must be
replaced. The blower motor and blower wheel are
each serviced separately.

REAR

DESCRIPTION

The rear blower motor and blower wheel are

mounted to a blower wheel housing located inside the
rear overhead A/C unit, above the headliner. The
blower motor controls the velocity of air flowing
through the overhead A/C unit by spinning a wide
squirrel cage-type blower wheel within the housing
at the selected speed. Rear blower motor speed is
controlled by regulating the ground path through the

rear blower motor switch and the rear blower motor
resistor.

OPERATION

The rear blower motor will only operate when the

ignition switch is in the On position. The rear blower
motor receives a fused battery feed through a fuse in
the relay and fuse block whenever the ignition switch
is in the On position. The relay and fuse block is
attached to the back of the junction block, under the
left side of the instrument panel in the passenger
compartment.

The rear blower motor, blower wheel, and blower

wheel housing cannot be repaired and, if faulty or
damaged, they must be replaced as a complete facto-
ry-balanced unit.

BLOWER MOTOR RELAY

DESCRIPTION

The blower motor relay (also referred to as Voltage

Reduction Relay or VRR) is an International Stan-
dards Organization (ISO)-type relay. The relay is an
electromechanical device that switches battery cur-
rent from a fuse in the Power Distribution Center
(PDC) directly to the blower motor. The relay is ener-
gized when the relay coil is provided a voltage signal
by the ignition switch. This arrangement reduces the
amount of battery current that must flow through
the ignition switch.

OPERATION

The blower motor relay control circuit is protected

by a fuse located in the junction block. When the
relay is de-energized, the blower motor receives no
battery current. The VRR is used to reduce blower
speeds in Heat mode. In non-A/C modes, the relay is
de-energized and switches the current flow through
an added resistance in the resistor block. When an
A/C mode is selected, the relay is energized and the
normally open contact is used to bypass the added
resistor. The fuse is located in the small relay fuse
block that is attached to the Junction Block. The
relay is energized by grounding the coil low side with
the HVAC switch in any A/C mode. See Blower Motor
Relay in the Diagnosis and Testing section of this
group for more information.

The blower motor relay is mounted with a single

screw directly to the instrument panel’s structural

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HEATING AND AIR CONDITIONING

plastic inside the glove box opening, next to the left-
side energy-absorbing bracket (Fig. 1). Refer to the
PDC label for blower motor relay identification and
location.

The blower motor relay (VRR) cannot be repaired

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

BLOWER MOTOR RESISTOR

FRONT

DESCRIPTION

During vehicle assembly, the blower motor resistor

is mounted to the dash plenum panel inside the pas-
senger

compartment

prior

instrument

panel

roll-up (Fig. 2). However, a resistor mounting plate
has been designed so that the resistor can be
removed through an access hole in the cowl plenum
panel just below the windshield. It can be accessed
by removing the cowl plenum cover/grille panel. See
Blower Motor Resistor in the Removal and Installa-
tion section of this group for more information.

OPERATION

The 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.

With the blower motor switch in the lowest speed

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
through the high speed blower motor relay.

The blower motor resistor cannot be repaired and,

if faulty or damaged, it must be replaced.

REAR

DESCRIPTION

The blower motor resistor for the optional rear

overhead A/C unit is located within the unit housing.
The 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.

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.

Fig. 1 Blower Motor Relay (VRR) Location

1 – BLOWER MOTOR RESISTOR CONNECTOR
2 – BLOWER MOTOR RELAY
3 – BLOWER MOTOR CONNECTOR
4 – GLOVE BOX LAMP CONNECTOR

Fig. 2 Blower Motor Resistor - Factory Installation

1 – PLENUM PANEL
2 – SCREW
3 – RESISTOR
4 – CONNECTOR
5 – SCREW
6 – RESISTOR MOUNTING PLATE

HEATING AND AIR CONDITIONING

24 - 3

DESCRIPTION AND OPERATION (Continued)

The blower motor resistor cannot be repaired and,

if faulty or damaged, it must be replaced.

BLOWER MOTOR SWITCH

FRONT

DESCRIPTION

The heater-A/C blower motor is controlled by a four

position rotary-type blower motor switch, mounted in
the heater-A/C control panel. The switch allows the
selection of one of four blower motor speeds, but can
only be turned off by selecting the Off position with
the heater-A/C mode control switch knob.

OPERATION

The blower motor switch directs the blower motor

ground path through the mode control switch to the
blower motor resistor, or directly to ground through
the high speed blower motor relay, as required to
achieve the selected blower motor speed.

The blower motor switch cannot be repaired and, if

faulty or damaged, the entire heater-A/C control unit
must be replaced. The blower motor switch knob is
serviced separately.

REAR

DESCRIPTION

The optional rear overhead A/C unit blower motor

is controlled by a four position rotary-type blower
motor switch, mounted by a snap fit in a hole in the
headliner over the right front seat back. The switch
allows the selection of one of three blower motor
speeds and an Off position. The blower motor switch
directs the blower motor ground path through the
blower motor resistor.

OPERATION

The blower motor switch cannot be repaired and, if

faulty or damaged, the entire switch unit must be
replaced. The blower motor switch has a replaceable
incandescent-type illumination lamp bulb.

COMPRESSOR

DESCRIPTION

The

air

conditioning

system

uses

Sanden

SD7H15 seven cylinder, reciprocating wobble plate-
type compressor on all models. This compressor has a
fixed displacement of 150 cubic centimeters (9.375
cubic inches), and has both the suction and discharge
ports located on the cylinder head. A label identifying
the use of R-134a refrigerant is located on the com-
pressor.

OPERATION

The compressor is driven by the engine through an

electric clutch, drive pulley and belt arrangement.
The compressor is lubricated by refrigerant oil that is
circulated throughout the refrigerant system with the
refrigerant.

The compressor draws in low-pressure refrigerant

vapor from the evaporator through its suction port. It
then compresses the refrigerant into a high-pressure,
high-temperature refrigerant vapor, which is then
pumped to the condenser through the compressor dis-
charge port.

The compressor cannot be repaired. If faulty or

damaged, the entire compressor assembly must be
replaced. The compressor clutch, pulley and clutch
coil are available for service.

COMPRESSOR CLUTCH

DESCRIPTION

The compressor clutch assembly consists of a sta-

tionary electromagnetic coil, a hub bearing and pul-
ley assembly, and a clutch plate (Fig. 3). The
electromagnetic coil unit and the hub bearing and
pulley assembly are each retained on the nose of the
compressor front housing with snap rings. The clutch
plate is mounted to the compressor shaft and secured
with a nut.

OPERATION

These components provide the means to engage

and disengage the compressor from the engine ser-
pentine accessory drive belt. When the clutch coil is

Fig. 3 Compressor Clutch - Typical

1 – CLUTCH PLATE
2 – SHAFT KEY
3 – PULLEY
4 – COIL
5 – CLUTCH SHIMS
6 – SNAP RING
7 – SNAP RING

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HEATING AND AIR CONDITIONING

DESCRIPTION AND OPERATION (Continued)

energized, it magnetically draws the clutch into con-
tact with the pulley and drives the compressor shaft.
When the coil is not energized, the pulley freewheels
on the clutch hub bearing, which is part of the pulley.
The compressor clutch and coil are the only serviced
parts on the compressor.

The compressor clutch engagement is controlled by

several components: the heater-A/C mode control
switch, the electronic cycling clutch switch, the low
pressure cut-off switch, the high pressure cut-off
switch, the compressor clutch relay, and the Power-
train Control Module (PCM). The PCM may delay
compressor clutch engagement for up to thirty sec-
onds. Refer to Group 14 - Fuel System for more infor-
mation on the PCM controls.

COMPRESSOR CLUTCH RELAY

DESCRIPTION

The compressor clutch relay is an International

Standards Organization (ISO) micro-relay. The termi-
nal designations and functions are the same as a con-
ventional

ISO

relay.

However,

the

micro-relay

terminal orientation (footprint) is different, the cur-
rent capacity is lower, and the relay case dimensions
are smaller than those of the conventional ISO relay.

OPERATION

The compressor clutch relay is an electromechani-

cal device that switches battery current to the com-
pressor clutch coil when the Powertrain Control
Module (PCM) grounds the coil side of the relay. The
PCM responds to inputs from the heater-A/C mode
control switch, the electronic cycling clutch switch,
the low pressure cut-off switch, and the high pres-
sure cut-off switch. See Compressor Clutch Relay in
the Diagnosis and Testing section of this group for
more information.

The compressor clutch relay is located in the Power

Distribution Center (PDC) in the engine compart-
ment. Refer to the PDC label for relay identification
and location.

The compressor clutch relay cannot be repaired

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

CONDENSER

DESCRIPTION

The condenser is located in the air flow in front of

the engine cooling radiator. The condenser is a heat
exchanger that allows the high-pressure refrigerant
gas being discharged by the compressor to give up its
heat to the air passing over the condenser fins.

OPERATION

When the refrigerant gas gives up its heat, it con-

denses. When the refrigerant leaves the condenser, it
has become a high-pressure liquid refrigerant. The
volume of air flowing over the condenser fins is crit-
ical to the proper cooling performance of the air con-
ditioning system. Therefore, it is important that
there are no objects placed in front of the radiator
grille openings in the front of the vehicle or foreign
material on the condenser fins that might obstruct
proper air flow. Also, any factory-installed air seals or
shrouds must be properly reinstalled following radia-
tor or condenser service.

The condenser cannot be repaired and, if faulty or

damaged, it must be replaced.

ELECTRONIC CYCLING CLUTCH SWITCH

DESCRIPTION

The Electronic Cycling Clutch Switch (ECCS) is

mounted to the outboard side of the thermal expan-
sion valve in the engine compartment. A thermistor
probe within a capillary tube on the switch is
inserted into a well on the side of the expansion
valve filled with a thermally-conductive grease. This
arrangement allows the ECCS to monitor the tem-
perature of the expanded refrigerant entering the
evaporator.

OPERATION

The function of the ECCS is to prevent refrigerant

temperatures from becoming so low that condensa-
tion freezes on the evaporator fins. This condition is
referred to as evaporator icing. Evaporator icing
reduces air conditioning system air flow and cooling
performance.

The ECCS is connected in series electrically with

the heater-A/C mode control switch, the low pressure
cut-off switch and the high pressure cut-off switch
between ground and the Powertrain Control Module
(PCM). The ECCS will open when it monitors a
refrigerant temperature below about 2.9° C (37.2° F),
and will close again when the refrigerant tempera-
ture reaches about 4.3° C (39.7° F). The opening and
closing of the ECCS signals the PCM to cycle the
compressor clutch on and off through the compressor
clutch relay.

The ECCS is a factory sealed and calibrated unit

and cannot be adjusted or repaired. If faulty or dam-
aged, the ECCS must be replaced.

HEATING AND AIR CONDITIONING

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DESCRIPTION AND OPERATION (Continued)

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