heater DODGE RAM 2002 Service Repair Manual

REMOVAL
The relays are located in engine compartment,
bolted to left inner fender below left battery (Fig. 30).
The mounting bracket and both relays are replaced
as an assembly.
(1) Disconnect both negative battery cables at both
batteries.
(2) Disconnect four relay trigger wires at both
relays (Fig. 30). Note position of wiring before remov-
ing.
(3) Lift four rubber shields from all 4 cables (Fig.
30).
(4) Remove four nuts at cable connectors (Fig. 30).
Note position of wiring before removing.
(5) Remove three relay mounting bracket bolts
(Fig. 30) and remove relay assembly.
INSTALLATION
The relays are located in engine compartment,
bolted to left inner fender below left battery (Fig. 30).
(1) Install relay assembly to inner fender. Tighten
mounting bolts to 4.5 N´m (40 in. lbs.) torque.
(2) Connect eight electrical connectors to relays.
(3) Connect battery cables to both batteries.
INTAKE AIR TEMPERATURE
SENSOR
DESCRIPTION - DIESEL
The intake manifold air temperature sensor is
installed into the rear of the intake manifold (Fig.
31) with the sensor element extending into the air
stream.
OPERATION - DIESEL
The IAT provides an input voltage to the Engine
Control Module (ECM) indicating intake manifold air
temperature. The input is used along with inputs
from other sensors for intake air heater element
operation, for engine protection, fuel timing and fuel
control. As the temperature of the air-fuel stream in
the manifold varies, the sensor resistance changes.
This results in a different input voltage to the ECM.
Fig. 29 Intake Manifold Air Heater Relays Location
1 - BATTERY (LEFT SIDE)
2 - RELAY MOUNTING BOLTS (3)
3 - RELAY TRIGGER WIRES (4)
4 - INTAKE AIR HEATER RELAYS (2)
5 - RUBBER SHIELDS (4)
6 - CABLES TO BATTERY (+)
Fig. 30 Intake Manifold Air Heater Relays
1 - BATTERY (LEFT SIDE)
2 - RELAY MOUNTING BOLTS (3)
3 - RELAY TRIGGER WIRES (4)
4 - INTAKE AIR HEATER RELAYS (2)
5 - RUBBER SHIELDS (4)
6 - CABLES TO BATTERY (+)
14 - 106 FUEL INJECTION - DIESELBR/BE
INTAKE AIR HEATER RELAY (Continued)

BRIGHT LIGHT LEAK TEST METHOD
Some water leaks in the luggage compartment can
be detected without water testing. Position the vehi-
cle in a brightly lit area. From inside the darkened
luggage compartment inspect around seals and body
seams. If necessary, have a helper direct a drop light
over the suspected leak areas around the luggage
compartment. If light is visible through a normally
sealed location, water could enter through the open-
ing.
PRESSURIZED LEAK TEST METHOD
When a water leak into the passenger compart-
ment cannot be detected by water testing, pressurize
the passenger compartment and soap test exterior of
the vehicle. To pressurize the passenger compart-
ment, close all doors and windows, start engine, and
set heater control to high blower in HEAT position. If
engine can not be started, connect a charger to the
battery to ensure adequate voltage to the blower.
With interior pressurized, apply dish detergent solu-
tion to suspected leak area on the exterior of the
vehicle. Apply detergent solution with spray device or
soft bristle brush. If soap bubbles occur at a body
seam, joint, seal or gasket, the leak entry point could
be at that location.
DIAGNOSIS AND TESTING - WIND NOISE
Wind noise is the result of most air leaks. Air leaks
can be caused by poor sealing, improper body compo-
nent alignment, body seam porosity, or missing plugs
in the engine compartment or door hinge pillar areas.
All body sealing points should be airtight in normal
driving conditions. Moving sealing surfaces will not
always seal airtight under all conditions. At times,
side glass or door seals will allow wind noise to be
noticed in the passenger compartment during highcross winds. Over compensating on door or glass
adjustments to stop wind noise that occurs under
severe conditions can cause premature seal wear and
excessive closing or latching effort. After a repair pro-
cedure has been performed, test vehicle to verify
noise has stopped before returning vehicle to use.
Wind noise can also be caused by improperly fitted
exterior moldings or body ornamentation. Loose
moldings can flutter, creating a buzzing or chattering
noise. An open cavity or protruding edge can create a
whistling or howling noise. Inspect the exterior of the
vehicle to verify that these conditions do not exist.
VISUAL INSPECTION BEFORE TESTS
Verify that floor and body plugs are in place and
body components are aligned and sealed. If compo-
nent alignment or sealing is necessary, refer to the
appropriate section of this group for proper proce-
dures.
ROAD TESTING WIND NOISE
(1) Drive the vehicle to verify the general location
of the wind noise.
(2) Apply 50 mm (2 in.) masking tape in 150 mm
(6 in.) lengths along weatherstrips, weld seams or
moldings. After each length is applied, drive the vehi-
cle. If noise goes away after a piece of tape is applied,
remove tape, locate, and repair defect.
POSSIBLE CAUSE OF WIND NOISE
²Moldings standing away from body surface can
catch wind and whistle.
²Gaps in sealed areas behind overhanging body
flanges can cause wind-rushing sounds.
²Misaligned movable components.
²Missing or improperly installed plugs in pillars.
²Weld burn through holes.
BR/BEBODY 23 - 3
BODY (Continued)

INSTRUMENT PANEL SYSTEM
TABLE OF CONTENTS
page page
INSTRUMENT PANEL SYSTEM
DESCRIPTION........................105
OPERATION..........................106
ASH RECEIVER
REMOVAL............................107
INSTALLATION........................107
CLUSTER BEZEL
REMOVAL............................108
INSTALLATION........................108
CUBBY BIN
REMOVAL............................108
INSTALLATION........................109
CUP HOLDER
REMOVAL............................109
INSTALLATION........................110
GLOVE BOX
REMOVAL
REMOVAL..........................110
DISASSEMBLY - GLOVE BOX...........110
ASSEMBLY - GLOVE BOX................111INSTALLATION........................111
GLOVE BOX LATCH STRIKER
REMOVAL............................111
INSTALLATION........................112
GLOVE BOX OPENING UPPER TRIM
REMOVAL............................112
INSTALLATION........................112
INSTRUMENT PANEL TOP COVER
REMOVAL............................113
INSTALLATION........................113
STEERING COLUMN OPENING COVER
REMOVAL............................113
INSTALLATION........................114
STORAGE BIN
REMOVAL............................114
INSTALLATION........................114
INSTRUMENT PANEL ASSEMBLY
REMOVAL............................115
INSTALLATION........................117
INSTRUMENT PANEL SYSTEM
DESCRIPTION
The instrument panel is located at the front of the
passenger compartment. This instrument panel is
molded from a blend of various plastics that are
mechanically attached to the vehicle. Colors are
molded into the plastic components to minimize
appearance degradation from scratches or abrasions.
The panel components are internally ribbed and riv-
eted to steel reinforcements for additional structural
integrity and dimensional stability. The instrument
panel surface components are designed to deform
upon impact without breaking. This type of construc-
tion provides improved energy absorption which, in
conjunction with the dual airbags and seat belts,
helps to improve occupant protection.
The top of the instrument panel is secured to the
top of the dash panel near the base of the windshield
using screws. An end bracket integral to each end of
the instrument panel structure is secured to each
cowl side inner panel with a screw. A stamped metal
bracket supports the center of the instrument panel
by securing it to the top of the floor panel transmis-
sion tunnel below the instrument panel with screws.
The instrument cluster, radio, heater-air conditioner
control, passenger airbag, glove box, electrical junc-tion block, Central Timer Module (CTM), accessory
switches, ash receiver, cigar lighter, accessory power
outlet, park brake release handle, inside hood release
handle, as well as numerous other components are
secured to and supported by this unit.
The instrument panel for this vehicle includes the
following major features:
²Cluster Bezel- This molded plastic bezel is
secured with snap clips to the instrument panel sup-
porting structure. It trims out the edges of the head-
lamp switch, instrument cluster, radio, heater-air
conditioner controls, passenger airbag on-off switch,
and the heated seat switches on vehicles so equipped.
On vehicles without the heated seat option, a small
storage cubby bin is provided in the cluster bezel.
This bezel also incorporates three completely adjust-
able panel outlets for the climate control system, and
fills the opening between the instrument cluster and
the top of the steering column where it passes
through the instrument panel.
²Cup Holder/Storage Bin- Vehicles equipped
with an automatic transmission feature a latching
fold-down, adjustable cup holder located on the lower
instrument panel between the glove box and the ash
receiver. Vehicles equipped with a manual transmis-
sion have a lighted storage bin on the instrument
panel in place of the cup holder.
BR/BEINSTRUMENT PANEL SYSTEM 23 - 105

²Glove Box- The hinged bin-type glove box in
the passenger side of the instrument panel features a
recessed paddle-operated latch handle. Three molded
hook formations on the lower edge of the glove box
door are engaged with and pivot on three hinge pins
integral to the lower edge of the instrument panel
support structure. The glove box door also serves as
the passenger side knee blocker. A honeycomb struc-
ture between the inner and outer glove box door pan-
els helps to absorb the impact load and distribute it
to the instrument panel structure.
²Steering Column Opening Cover- The steer-
ing column opening cover serves as the driver side
knee blocker. This molded plastic cover has an inte-
gral ribbed plastic liner concealed behind it, for
increased strength and integrity. The steering column
opening cover transfers impact loads to the instru-
ment panel structural support.
²Top Cover- The instrument panel top cover or
base trim is the molded, grained, and color impreg-
nated plastic outer skin of the instrument panel
structural support.
Hard wired circuitry connects the electrical compo-
nents on the instrument panel to each other through
the electrical system of the vehicle. These hard wired
circuits are integral to several wire harnesses, which
are routed throughout the vehicle and retained by
many different methods. These circuits may be con-
nected to each other, to the vehicle electrical system
and to the instrument panel components through the
use of a combination of soldered splices, splice block
connectors and many different types of wire harness
terminal connectors and insulators. Refer to the
appropriate wiring information. The wiring informa-
tion includes complete circuit diagrams, proper wire
and connector repair procedures, further details on
wire harness routing and retention, as well as pin-
out and location views for the various wire harness
connectors, splices, and grounds.
OPERATION
The instrument panel serves as the command cen-
ter of the vehicle, which necessarily makes it a very
complex unit. The instrument panel is designed to
house the controls and monitors for standard and
optional powertrains, climate control systems, audio
systems, safety systems, and many other comfort or
convenience items. When the components of the
instrument panel structural support are properly
assembled and secured in the vehicle they provide
superior instrument panel stiffness and integrity to
help reduce buzzes, squeaks, and rattles. This type of
construction also provides improved energy absorp-
tion which, in conjunction with the dual airbags and
seat belts, helps to improve occupant protection.The instrument panel is also designed so that all of
the various controls can be safely reached and the
monitors can be easily viewed by the vehicle operator
when driving, while still allowing relative ease of
access to each of these items for service. Modular
instrument panel construction allows all of the
gauges and controls to be serviced from the front of
the panel. In addition, most of the instrument panel
electrical components can be accessed without com-
plete instrument panel removal. However, if neces-
sary, the instrument panel can be removed from the
vehicle as an assembly.
The steering column opening cover with its inte-
gral knee blocker located on the driver side of the
instrument panel works in conjunction with the air-
bag system in a frontal vehicle impact to keep the
driver properly positioned for an airbag deployment.
In addition, removal of this component provides
access to the steering column mounts, the steering
column wiring, the Junction Block (JB) (removal of a
snap-fit fuse access panel on the left end of the
instrument panel allows access to the fuses and cir-
cuit breakers), the Central Timer Module (CTM), the
Infinity speaker filter choke and relay unit, much of
the instrument panel wiring, and the gear selector
indicator cable (automatic transmission).
In a frontal collision, the glove box door on the pas-
senger side of the instrument panel provides the
same function for the front seat passenger as the
knee blocker does for the driver. The glove box door
also incorporates a recessed latch handle. Removal of
the glove box provides access to the passenger airbag,
the glove box lamp and switch, the radio antenna
coaxial cable, the heating and air conditioning vac-
uum harness connector, and additional instrument
panel wiring.
Removal of the instrument panel cluster bezel
allows access to the headlamp switch, instrument
cluster, radio, passenger airbag on-off switch, heated
seat switches (if equipped), and the heating and air
conditioning control. Removal of the instrument clus-
ter allows access to the cluster illumination and indi-
cator bulbs, and more of the instrument panel
wiring. Complete instrument panel removal is
required for service of most components internal to
the heating and air conditioning system housing,
including the heater core and the evaporator.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of all of the components and systems mounted on or
in the instrument panel.
23 - 106 INSTRUMENT PANEL SYSTEMBR/BE
INSTRUMENT PANEL SYSTEM (Continued)

left cowl side inner panel. (Refer to 5 - BRAKES/
PARKING BRAKE/RELEASE - REMOVAL).
(b) Disconnect the instrument panel wire har-
ness connector from the park brake switch on the
park brake mechanism.
(c) Disconnect the three connectors (one from the
body wire harness, and two from the headlamp and
dash wire harness) from the three connector recep-
tacles located closest to the dash panel on the back
of the Junction Block (JB).
(d) Remove the screw from the center of the
headlamp and dash wire harness to instrument
panel wire harness bulkhead connector and discon-
nect the connector.
(e) Disconnect the instrument panel wire har-
ness to door wire harness connector located directly
below the instrument panel wire harness to head-
lamp and dash wire harness bulkhead connector.
(f) If the vehicle is equipped with the Infinity
sound system option, disconnect the Infinity wire
harness connector from the instrument panel wire
harness connector that is secured to the outboard
side of the instrument panel wire harness to head-
lamp and dash wire harness bulkhead connector.(g) Disconnect the instrument panel wire har-
ness connector from the stop lamp switch.
(h) Disconnect the heater-A/C housing vacuum
harness connector from the heater-A/C control vac-
uum harness connector located near the left end of
the heater-A/C housing.
(10) From under the passenger side of the instru-
ment panel, disconnect the two halves of the radio
antenna coaxial cable connector.
(11) Loosen the right and left instrument panel
cowl side roll-down bracket screws about 13 mm
(0.50 inch) (Fig. 11).
(12) Remove the five screws that secure the top of
the instrument panel to the top of the dash panel,
removing the center screw last.
(13) Roll down the instrument panel and install a
temporary hook in the center hole on top of the
instrument panel. Secure the other end of the hook
to the center hole in the top of the dash panel. The
hook should support the instrument panel in its
rolled down position about 46 cm (18 inches) from
the dash panel.
(14) With the instrument panel supported in the
roll-down position, disconnect the instrument panel
Fig. 11 Instrument Panel Assembly Remove/Install
1 - PLASTIC NUT
2 - SCREWS3 - SCREWS
23 - 116 INSTRUMENT PANEL SYSTEMBR/BE
INSTRUMENT PANEL ASSEMBLY (Continued)

wire harness connectors from the heater-A/C housing
wire harness connectors.
(15) With the aid of an assistant, remove the tem-
porary hook and lift the instrument panel assembly
off of the roll-down bracket screws and remove it
from the vehicle.
INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPT-
ING ANY STEERING WHEEL, STEERING COLUMN,
SEAT BELT TENSIONER, 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 PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS
THE ONLY SURE WAY TO DISABLE THE AIRBAG SYS-
TEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN ACCIDENTAL AIRBAG DEPLOY-
MENT AND POSSIBLE PERSONAL INJURY.
(1)With the aid of an assistant, load the instrument
panel assembly onto the roll-down bracket screws on
the cowl side inner panels in the vehicle (Fig. 11).
Install a temporary hook in the center hole on top of the
instrument panel. Secure the other end of the hook to
the center hole in the top of the dash panel. The hook
should support the instrument panel in its rolled down
position about 46 cm (18 inches) from the dash panel.
(2) With the instrument panel supported in the
roll-down position, reconnect the instrument panel
wire harness connectors to the heater-A/C housing
wire harness connectors.
(3) Remove the temporary hook from the instru-
ment panel and roll the instrument panel up to its
installed position against the dash panel.
(4) Install and tighten the five screws that secure
the top of the instrument panel to the top of the dash
panel. Tighten the screws to 3.2 N´m (28 in. lbs.).
(5) Tighten the right and left instrument panel
cowl side roll-down bracket screws. Tighten the
screws to 11.9 N´m (105 in. lbs.).
(6) From under the passenger side of the instru-
ment panel, reconnect the two halves of the radio
antenna coaxial cable connector.
(7) From under the driver side of the instrument
panel, perform the following:
(a) Engage the park brake release handle link-
age rod with the park brake mechanism on the left
cowl side inner panel. (Refer to 5 - BRAKES/PARK-
ING BRAKE/RELEASE - INSTALLATION).
(b) Reconnect the instrument panel wire harness
connector to the park brake switch on the park
brake mechanism.(c) Reconnect the three connectors (one from the
body wire harness, and two from the headlamp and
dash wire harness) to the three connector recepta-
cles located closest to the dash panel on the back of
the Junction Block (JB).
(d)
Reconnect the headlamp and dash wire harness
to instrument panel wire harness bulkhead connector
and tighten the screw in the center of the connector.
Tighten the screw to 3.5 N´m (31 in. lbs.).
(e) Reconnect the instrument panel wire harness
to door wire harness connector located directly
below the instrument panel wire harness to head-
lamp and dash wire harness bulkhead connector.
(f) If the vehicle is equipped with the Infinity
sound system option, reconnect the Infinity wire
harness connector to the instrument panel wire
harness connector that is secured to the outboard
side of the instrument panel wire harness to head-
lamp and dash wire harness bulkhead connector.
(g) Reconnect the instrument panel wire harness
connector to the stop lamp switch.
(h) Reconnect the heater-A/C housing vacuum
harness connector to the heater-A/C control vac-
uum harness connector located near the left end of
the heater-A/C housing.
(8) Reinstall the steering column into the vehicle.
Be certain that the steering wheel was locked and
secured from rotation to prevent the loss of clock-
spring centering. (Refer to 19 - STEERING/COL-
UMN - INSTALLATION).
(9) If the vehicle is so equipped, reconnect the
overdrive lockout switch pigtail wire connector to the
instrument panel wire harness connector near the
instrument panel lower reinforcement.
(10) Reconnect the clockspring pigtail wire connec-
tor to the instrument panel wire harness connector
at the instrument panel lower reinforcement.
(11) Position the inside hood latch release handle
to the instrument panel lower reinforcement.
(12) Install and tighten the two screws that secure
the inside hood latch release handle to the instru-
ment panel lower reinforcement. Tighten the screws
to 2.8 N´m (25 in. lbs.).
(13) Reinstall the steering column opening cover
onto the instrument panel. (Refer to 23 - BODY/IN-
STRUMENT PANEL/STEERING COLUMN OPEN-
ING COVER - INSTALLATION).
(14) Reinstall the trim onto the left and right cowl
side inner panels. (Refer to 23 - BODY/INTERIOR/
COWL TRIM COVER - INSTALLATION).
(15) Reinstall the Airbag Control Module (ACM)
and bracket onto the floor panel transmission tunnel.
(Refer to 8 - ELECTRICAL/RESTRAINTS/AIRBAG
CONTROL MODULE - INSTALLATION).
(16) Reconnect the battery negative cable.
BR/BEINSTRUMENT PANEL SYSTEM 23 - 117
INSTRUMENT PANEL ASSEMBLY (Continued)

HEATING & AIR CONDITIONING
TABLE OF CONTENTS
page page
HEATING & AIR CONDITIONING
DESCRIPTION...........................1
OPERATION.............................1
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - A/C
PERFORMANCE........................2
DIAGNOSIS AND TESTING - HEATER
PERFORMANCE........................6STANDARD PROCEDURE
STANDARD PROCEDURE - DIODE
REPLACEMENT.........................7
SPECIFICATIONS.........................7
CONTROLS.............................9
DISTRIBUTION..........................30
PLUMBING.............................40
HEATING & AIR
CONDITIONING
DESCRIPTION - HEATER AND AIR
CONDITIONER
All vehicles are equipped with a common HVAC
housing assembly (Fig. 1). The system combines air
conditioning, heating, and ventilating capabilities in
a single unit housing mounted under the instrument
panel. On heater-only systems, the evaporator coil
and recirculation door are omitted from the housing.
DESCRIPTION - COOLING SYSTEM
REQUIREMENTS
To maintain the performance level of the HVAC
system, the engine cooling system must be properly
maintained. The use of a bug screen is not recom-
mended. Any obstructions in front of the radiator orcondenser will reduce the performance of the air con-
ditioning and engine cooling systems.
The engine cooling system includes the heater core
and the heater hoses. Refer to Engine Cooling for
more information before the opening of, or attempt-
ing any service to the engine cooling system.
DESCRIPTION - REFRIGERANT SYSTEM
SERVICE PORT
The two refrigerant system service ports are used
to charge, recover/recycle, evacuate, and test the air
conditioning refrigerant system. Unique service port
coupler sizes are used on the R-134a system, to
ensure that the refrigerant system is not accidentally
contaminated by the use of the wrong refrigerant
(R-12), or refrigerant system service equipment.
OPERATION - HEATER AND AIR CONDITIONER
The heater and optional air conditioner are blend-
air type systems. In a blend-air system, a blend door
controls the amount of unconditioned air (or cooled
air from the evaporator on models with air condition-
ing) that is allowed to flow through, or around, the
heater core. A temperature control knob on the A/C
Heater control panel determines the discharge air
temperature by controlling an electric actuator,
which moves the blend door. This allows an almost
immediate control of the output air temperature of
the system.
The mode control knob on the heater-only or A/C
Heater control panel is used to direct the conditioned
air to the selected system outlets. Both mode control
switches use engine vacuum to control the mode
doors, which are operated by vacuum actuators.
On air conditioned vehicles, the outside air intake
can be shut off by selecting the Recirculation Mode
with the mode control knob. This will operate a vac-
uum actuated recirculation door that closes off the
outside fresh air intake and recirculates the air that
is already inside the vehicle.
Fig. 1 COMMON BLEND-AIR HEATER-AIR
1 - HEATER CORE
2 - BLEND DOOR
3 - EVAPORATOR (A/C ONLY)
4 - RECIRCULATION DOOR (A/C ONLY)
5 - FLOOR/PANEL DOOR
6 - FLOOR/DEFROST DOOR
BR/BEHEATING & AIR CONDITIONING 24 - 1

The optional air conditioner for all models is
designed for the use of non-CFC, R-134a refrigerant.
The air conditioning system has an evaporator to cool
and dehumidify the incoming air prior to blending it
with the heated air. This air conditioning system
uses a fixed orifice tube in the middle of the liquid
line to meter refrigerant flow to the evaporator coil.
To maintain minimum evaporator temperature and
prevent evaporator freezing, the a/c low pressure
switch on the accumulator cycles the compressor
clutch.
OPERATION - REFRIGERANT SYSTEM SERVICE
PORT
The high pressure service port is located on the liq-
uid line between the condenser and the evaporator,
near the front of the engine compartment. The low
pressure service port is located on the suction line,
near the accumulator outlet.
Each of the service ports has a threaded plastic
protective cap installed over it from the factory. After
servicing the refrigerant system, always reinstall
both of the service port caps.
DIAGNOSIS AND TESTING - A/C
PERFORMANCE
The air conditioning system is designed to provide
the passenger compartment with low temperature
and low humidity air. The evaporator, located in the
HVAC housing on the dash panel below the instru-
ment panel, is cooled to temperatures near the freez-
ing point. As warm damp air passes through the
cooled evaporator, the air transfers its heat to the
refrigerant in the evaporator tubes and the moisture
in the air condenses on the evaporator fins. During
periods of high heat and humidity, an air condition-
ing system will be more effective in the recirculation
mode (Max-A/C). With the system in the recirculation
mode, only air from the passenger compartment
passes through the evaporator. As the passenger com-
partment air dehumidifies, the air conditioning sys-
tem performance levels improve.
Humidity has an important bearing on the temper-
ature of the air delivered to the interior of the vehi-
cle. It is important to understand the effect that
humidity has on the performance of the air condition-
ing system. When humidity is high, the evaporator
has to perform a double duty. It must lower the air
temperature, and it must lower the temperature of
the moisture in the air that condenses on the evapo-
rator fins. Condensing the moisture in the air trans-
fers heat energy into the evaporator fins and tubing.This reduces the amount of heat the evaporator can
absorb from the air. High humidity greatly reduces
the ability of the evaporator to lower the temperature
of the air.
However, evaporator capacity used to reduce the
amount of moisture in the air is not wasted. Wring-
ing some of the moisture out of the air entering the
vehicle adds to the comfort of the passengers.
Although, an owner may expect too much from their
air conditioning system on humid days. A perfor-
mance test is the best way to determine whether the
system is performing up to standard. This test also
provides valuable clues as to the possible cause of
trouble with the air conditioning system.
Before proceeding, (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - WARNING) and
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - CAUTION). The air temperature in
the test room and in the vehicle must be a minimum
of 21É C (70É F) for this test.
(1) Connect a tachometer and a manifold gauge
set.
(2) Set the a/c heater mode control switch knob to
the recirculation mode (Max-A/C) position, the tem-
perature control knob to the full cool position, and
the blower motor switch to the highest speed posi-
tion.
(3) Start the engine and hold the idle speed at
1,000 rpm with the compressor clutch engaged. If the
compressor clutch does not engage, (Refer to 24 -
HEATING & AIR CONDITIONING/CONTROLS/A/C
COMPRESSOR CLUTCH COIL - DIAGNOSIS AND
TESTING).
(4) The engine should be at operating temperature.
The doors and windows must be closed and the hood
must be mostly closed.
(5) Insert a thermometer in the driver side center
A/C (panel) outlet. Operate the engine for five min-
utes.
(6) The compressor clutch may cycle, depending
upon the ambient temperature and humidity. If the
clutch cycles, unplug the a/c low pressure switch wire
harness connector from the switch located on the
accumulator (Fig. 2). Place a jumper wire between
the two cavities of the a/c low pressure switch wire
harness connector.
24 - 2 HEATING & AIR CONDITIONINGBR/BE
HEATING & AIR CONDITIONING (Continued)

(7) With the compressor clutch engaged, record the
panel outlet discharge air temperature, the discharge
pressure (high side), and the suction pressure (low
side).
(8) Compare the panel outlet discharge air temper-
ature reading to the Performance Temperature and
Pressure chart. If the temperature reading is high,
clamp off both heater hoses (inlet and outlet), wait
five minutes and record the temperature again. Com-
pare the second reading to the Performance Temper-
ature and Pressure chart. If the temperature reading
is now OK, see Temperature Control Cable in the
Removal and Installation section and in the Adjust-
ments section of this group. If the temperature read-
ing is still too high, (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - DIAGNOSIS AND
TESTING), and (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE) in this group.
Performance Temperature and Pressure
Ambient Temperature21É C
(70É F)27É C
(80É F)32É C
(90É F)38É C
(100É F)43É C
(110É F)49É C
(120É F)
Center Panel OutletDischarge
Air Temperature5to7ÉC
(40 to 45É
F)13 to 16É
C
(55 to 60É
F)16 to 21É
C
(60 to 70É
F)21 to 24É
C
(70 to 75É
F)27 to 29É
C
(80 to 85É
F)29 to 32É C
(85 to 90É
F)
*Suction Pressure (Low Side)241 to 276
kPa
(35 to 40
psi)276 to 345
kPa
(40 to 50
psi)345 to 414
kPa
(50 to 60
psi)414 to 483
kPa
(60 to 70
psi)483 to 552
kPa
(70 to 80
psi)552 to 586
kPa
(85 to 90
psi)
*Discharge Pressure (High
Side)931 to
1000 kPa
(135 to
145 psi)1207 to
1482 kPa
(175 to
215 psi)1482 to
1862 kPa
(215 to
270 psi)1862 to
2275 kPa
(270 to
330 psi)2344 to
2551 kPa
(340 to
370 psi)2758 to
2965 kPa
(400 to 430
psi)
*Note: If pressures are lower than shown, but center panel outlet discharge air temperatures are OK, then the A/C
system is OK.
(9) Compare the discharge (high side) and suction
(low side) pressure readings to the Performance Tem-perature and Pressure chart. If the pressures are
abnormal, see the A/C Diagnosis chart.
A/C Diagnosis
Condition Possible Causes Correction
RAPID COMPRESSOR
CLUTCH CYCLING (TEN
OR MORE CYCLES PER
MINUTE).1. Low refrigerant system
charge.1. (Refer to Plumbing/Diagnosis and Testing - Refrigerant
System Leaks) in this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
Fig. 2 A/C LOW PRESSURE SWITCH
1 - A/C LOW PRESSURE SWITCH
2 - ACCUMULATOR
BR/BEHEATING & AIR CONDITIONING 24 - 3
HEATING & AIR CONDITIONING (Continued)

A/C Diagnosis
Condition Possible Causes Correction
2. Faulty a/c low
pressure switch.2. (Refer to Controls/A/C Low Pressure Switch/Diagnosis
and Testing) in this group. Test the a/c low pressure
switch and replace, if required.
3. Faulty Powertrain
Control Module (PCM).3. (Refer to Appropriate Diagnostic Information) for testing
the PCM. Test the PCM and replace, if required.
EQUAL PRESSURES,
BUT THE
COMPRESSOR CLUTCH
DOES NOT ENGAGE.1. No refrigerant in the
refrigerant system.1. (Refer to Plumbing/Diagnosis and Testing - Refrigerant
System Leaks) in this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
2. Faulty fuse. 2. Check the fuses in the Power Distribution Center and
the junction block. Repair the shorted circuit or
component and replace the fuses, if required.
3. Faulty a/c compressor
clutch coil.3. (Refer to Controls/A/C Compressor Clutch Coil/
Diagnosis and Testing) in this group. Test the compressor
clutch coil and replace, if required.
4. Faulty a/c compressor
clutch relay.4. (Refer to Controls/A/C Compressor Clutch Relay/
Diagnosis and Testing) in this group. Test the compressor
clutch relay and relay circuits. Repair the circuits or
replace the relay, if required.
5. Improperly installed or
faulty a/c low pressure
switch.5. (Refer to Controls/A/C Low Pressure Switch/Diagnosis
and Testing) in this group. Test the a/c low pressure
switch and tighten or replace, if required.
6. Faulty a/c high
pressure switch.6. (Refer to Controls/A/C High Pressure Switch/Diagnosis
and Testing) in this group. Test the a/c high pressure
switch and replace, if required.
7. Faulty Powertrain
Control Module (PCM).7. (Refer to Appropriate Diagnostic Information) for testing
the PCM. Test the PCM and replace, if required.
8. Faulty a/c heater
control.8. (Refer to Controls/A/C Heater Control/Diagnosis and
Testing) in this group. Test the a/c heater control and
replace, if required.
NORMAL PRESSURES,
BUT A/C
PERFORMANCE TEST
AIR TEMPERATURES AT
CENTER PANEL
OUTLET ARE TOO
HIGH.1. Excessive refrigerant
oil in system.1. (Refer to Plumbing/Refrigerant Oil/Standard Procedure
- Refrigerant Oil Level) in this group. Recover the
refrigerant from the refrigerant system and inspect the
refrigerant oil content. Restore the refrigerant oil to the
proper level, if required.
2. Blend door actuator
inoperative or faulty.2. Check the Blend Door Actuator operation. Replace as
required.
3. Blend door
inoperative, obstructed or
sealing improperly.3. (Refer to Distribution/Blend Door/Removal/Installation)
in this group. Inspect the blend door for proper operation
and sealing and correct, if required.
LOW SIDE PRESSURE
IS NORMAL OR
SLIGHTLY LOW, AND
HIGH SIDE PRESSURE
IS TOO LOW.1. Low refrigerant system
charge.1. (Refer to Plumbing/Diagnosis and Testing - Refrigerant
System Leaks) in this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
24 - 4 HEATING & AIR CONDITIONINGBR/BE
HEATING & AIR CONDITIONING (Continued)