1998 DODGE RAM 1500 Passenger Window

ber above the heating, ventilation and air condition-
ing (HVAC) housing. On models equipped with air
conditioning, the air passes through the evaporator
coil. Air flow can be directed either through or
around the heater core. This is done by adjusting the
blend door with the temperature control knob on the
A/C-heater control located the instrument panel. The
air flow can then be directed from the panel, floor
and defrost outlets in various combinations using the
mode control knob located on the A/C-heater control.
Air flow velocity can be adjusted with the blower
speed selector located on the A/C-heater control.
NOTE: It is important to keep the air intake opening
clear of debris. Leaf particles and other debris that
is small enough to pass through the cowl opening
screen can accumulate within the HVAC housing.
The closed, warm, damp and dark environment cre-
ated within the housing is ideal for the growth of
certain molds, mildews and other fungi. Any accu-mulation of decaying plant matter provides an addi-
tional food source for fungal spores, which enter
the housing with the fresh intake-air. Excess debris,
as well as objectionable odors created by decaying
plant matter and growing fungi can be discharged
into the passenger compartment during heater-A/C
operation if the air intake opening is not kept clear
of debris.
The heater and air conditioning systems 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 determines
the discharge air temperature by actuating an elec-
tric motor, which operates the blend door. This allows
an almost immediate control of the output air tem-
perature of the system.
On all models, the outside air intake can be shut
off by selecting the Recirculation Mode with the
mode control knob. This will operate a electric actu-
ated recirculation air door that closes off the outside
fresh air intake and recirculates the air that is
already inside the vehicle.
The air conditioning compressor can be engaged in
any mode by pressing the snowflake, A/C on/off but-
ton. It can also be engaged by placing the mode con-
trol in the mix to defrost positions. This will remove
heat and humidity from the air before it is directed
through or around the heater core. The mode control
knob on the A/C-heater control is used to also direct
the conditioned air to the selected system outlets.
The mode control switch uses an electric motor to
control the mode doors.
The defroster outlet receives airflow from the
HVAC housing through the molded plastic defroster
duct, which connects to the HVAC housing defroster
outlet. The airflow from the defroster outlets is
directed by fixed vanes in the defroster outlet grilles
and cannot be adjusted. The defroster outlet grilles
are integral to the instrument panel top cover.
The side window demister outlets receive airflow
from the HVAC housing through the molded plastic
defroster duct and two molded plastic demister ducts.
The airflow from the side window demister outlets is
directed by fixed vanes in the demister outlet grilles
and cannot be adjusted. The side window demister
outlet grilles are integral to the instrument panel.
The demisters direct air from the HVAC housing
through the outlets located on the top corners of the
instrument panel. The demisters operate when the
mode control knob is positioned in the floor-defrost
and defrost-only settings. Some air may be noticeable
from the demister outlets when the mode control is
in the bi-level to floor positions.
Fig. 1 HVAC Housing - Dual Zone Shown, Single
Zone Typical
1 - NUT
2 - PASSENGER BLEND DOOR ACTUATOR
3 - NUT
4 - INLET BAFFLE
5 - RECIRCULATION DOOR ACTUATOR
6 - RECIRCULATION DOOR
7 - DRIVER SIDE BLEND DOOR ACTUATOR
8 - HVAC HOUSING
9 - BOLT
10 - DEFROSTER DOOR ACTUATOR
11 - MODE DOOR ACTUATOR
24 - 2 HEATING & AIR CONDITIONINGDR
HEATING & AIR CONDITIONING (Continued)

The panel outlets receive airflow from the HVAC
housing through a molded plastic main panel duct,
center panel duct and two end panel ducts. The two
end panel ducts direct airflow to the left and right
instrument panel outlets, while the center panel duct
directs airflow to the two center panel outlets. Each
of these outlets can be individually adjusted to direct
the flow of air.
The floor outlets receive airflow from the HVAC
housing through the floor distribution duct. The front
floor outlets are integral to the molded plastic floor
distribution duct, which is secured to the bottom of
the housing. The floor outlets cannot be adjusted.
The air conditioner for all models is designed for
the use of non-CFC, R-134a refrigerant. The air con-
ditioning system has an evaporator to cool and dehu-
midify the incoming air prior to blending it with the
heated air. This air conditioning system uses a fixed
orifice tube in the liquid line near the condenser out-
let tube to meter refrigerant flow to the evaporator
coil. To maintain minimum evaporator temperature
and prevent evaporator freezing, a evaporator tem-
perature sensor is used. The JTEC control module is
programmed to respond to the evaporator tempera-
ture sensor input by cycling the air conditioning com-
pressor clutch as necessary to optimize air
conditioning system performance and to protect the
system from evaporator freezing.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - A/C
PERFORMANCE
The air conditioning system is designed to remove
heat and humidity from the air entering the passen-
ger compartment. The evaporator, located in the
HVAC housing, is cooled to temperatures near the
freezing point. As warm damp air passes over the
fins in the evaporator, moisture in the air condenses
to water, dehumidifying the air. Condensation on the
evaporator fins reduces the evaporators ability to
absorb heat. During periods of high heat and humid-
ity, an air conditioning system will be less effective.
With the instrument control set to Recirculation
mode, only air from the passenger compartment
passes through the evaporator. As the passenger com-
partment air dehumidifies, A/C performance levels
rise.
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 ofthe 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.
PERFORMANCE TEST PROCEDURE
Review Safety Warnings and Cautions before per-
forming this procedure (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - WARNING) and
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - CAUTION). Air temperature in test
room and on vehicle must be 21É C (70É F) minimum
for this test.
NOTE: When connecting the service equipment
coupling to the line fitting, verify that the valve of
the coupling is fully closed. This will reduce the
amount of effort required to make the connection.
(1) Connect a tachometer and a manifold gauge set
or A/C recycling/charging station.
(2) Set the A/C-heater mode control in the Recircu-
lation Mode position, the temperature control knob in
the full cool position, and the blower motor switch to
the highest speed position.
(3) Start the engine and hold at 1,000 rpm with
the A/C compressor clutch engaged.
(4) The engine should be warmed up to operating
temperature with the doors closed and windows
open.
(5) Insert a thermometer in the driver side center
panel A/C-heater outlet and operate the engine for
five minutes.
(6) The compressor clutch may cycle, depending
upon the ambient temperature and humidity.
(7) With the compressor clutch engaged, record the
discharge air temperature and the compressor dis-
charge pressure.
(8) If the discharge air temperature fails to meet
the specifications in the A/C Performance Tempera-
ture chart, refer to the Pressure Diagnosis chart.
DRHEATING & AIR CONDITIONING 24 - 3
HEATING & AIR CONDITIONING (Continued)

SUPPLEMENTAL RESTRAINTS -
STANDARD PROCEDURE, HANDLING
NON-DEPLOYED......................8O-6
SUPPLIES - DESCRIPTION, 5 VOLT......8E-10
SUPPLIES - OPERATION, 5 VOLT........8E-11
SUPPLY TEST - DIAGNOSIS AND
TESTING, VACUUM....................8P-2
SUPPORT - INSTALLATION, SUN VISOR . . . 23-71
SUPPORT - REMOVAL, SUN VISOR......23-70
SUPPORT BRACKET - INSTALLATION,
REAR VIEW MIRROR.................23-70
SUPPORT BRACKET - INSTALLATION,
STEERING COLUMN OPENING..........23-60
SUPPORT BRACKET - REMOVAL,
STEERING COLUMN OPENING..........23-60
SUPPORT CYLINDER - INSTALLATION....23-48
SUPPORT CYLINDER - INSTALLATION,
LOAD FLOOR........................23-72
SUPPORT CYLINDER - REMOVAL........23-48
SUPPORT CYLINDER - REMOVAL, LOAD
FLOOR.............................23-72
SUPPORT HANDLE/BEZEL -
INSTALLATION, LUMBAR..............23-82
SUPPORT HANDLE/BEZEL - REMOVAL,
LUMBAR...........................23-82
SUPPORT PLATE - INSTALLATION........5-36
SUPPORT PLATE - REMOVAL............5-35
SUPPRESSION GROUND STRAP -
DESCRIPTION, RADIO NOISE............8A-9
SUPPRESSION GROUND STRAP -
INSTALLATION, RADIO NOISE...........8A-10
SUPPRESSION GROUND STRAP -
OPERATION, RADIO NOISE..............8A-9
SUPPRESSION GROUND STRAP -
REMOVAL, RADIO NOISE...............8A-9
SURFACE PREPARATION - STANDARD
PROCEDURE, ENGINE GASKET...........9-10
SURROUND - INSTALLATION,
INSTRUMENT PANEL LOWER...........23-59
SURROUND - REMOVAL, INSTRUMENT
PANEL LOWER......................23-59
SUSPENSION - DESCRIPTION, GEAR -
INDEPENDENT FRONT.................19-17
SUSPENSION - INSTALLATION, GEAR -
INDEPENDENT FRONT.................19-18
SUSPENSION - REMOVAL, GEAR -
INDEPENDENT FRONT.................19-17
SUSPENSION - STANDARD PROCEDURE,
ALIGNMENT LINK/COIL..................2-5
SUSPENSION ARM - INSTALLATION,
LOWER.............................2-38
SUSPENSION ARM - REMOVAL, LOWER . . . 2-38
SUSPENSION, SPECIAL TOOLS - FRONT . . . 2-12
SWITCH - DESCRIPTION................8P-7
SWITCH - DESCRIPTION, BACKUP LAMP . . . 8L-8
SWITCH - DESCRIPTION, BLOWER
MOTOR............................24-20
SWITCH - DESCRIPTION, BRAKE LAMP....8L-9
SWITCH - DESCRIPTION, CLUTCH
PEDAL POSITION.....................6-13
SWITCH - DESCRIPTION, DOOR AJAR....8L-27
SWITCH - DESCRIPTION, DRIVER SEAT . . . 8N-14
SWITCH - DESCRIPTION, HAZARD.......8L-14
SWITCH - DESCRIPTION, HEADLAMP....8L-14
SWITCH - DESCRIPTION, HEATED SEAT . . 8G-11
SWITCH - DESCRIPTION, HORN
..........8H-2
SWITCH - DESCRIPTION, IGNITION
.......19-9
SWITCH - DESCRIPTION, KEY-IN
IGNITION
...........................19-11
SWITCH - DESCRIPTION, LUMBAR
CONTROL
..........................8N-17
SWITCH - DESCRIPTION, PASSENGER
AIRBAG ON/OFF
.....................8O-42
SWITCH - DESCRIPTION, PASSENGER
SEAT
..............................8N-15
SWITCH - DESCRIPTION, POWER
STEERING PRESSURE
.................19-46
SWITCH - DESCRIPTION, PTO
.....14-36,14-85
SWITCH - DESCRIPTION, REAR
WINDOW DEFOGGER
..................8G-4
SWITCH - DESCRIPTION, SEAT BELT
.....8O-51
SWITCH - DESCRIPTION, SELECTOR
....21-510,
21-539,21-574
SWITCH - DESCRIPTION, TOW/HAUL
OVERDRIVE
..................21-261,21-392
SWITCH - DESCRIPTION, WASHER
FLUID LEVEL
.........................8R-9SWITCH - DIAGNOSIS AND TESTING,
BACKUP LAMP.......................8L-8
SWITCH - DIAGNOSIS AND TESTING,
BLOWER MOTOR....................24-20
SWITCH - DIAGNOSIS AND TESTING,
BRAKE LAMP.......................8L-10
SWITCH - DIAGNOSIS AND TESTING,
CLUTCH PEDAL POSITION..............6-13
SWITCH - DIAGNOSIS AND TESTING,
DRIVER SEAT.......................8N-14
SWITCH - DIAGNOSIS AND TESTING,
HEATED SEAT .......................8G-12
SWITCH - DIAGNOSIS AND TESTING,
HORN..............................8H-2
SWITCH - DIAGNOSIS AND TESTING,
IGNITION............................19-9
SWITCH - DIAGNOSIS AND TESTING,
MULTI-FUNCTION....................8L-18
SWITCH - DIAGNOSIS AND TESTING,
PASSENGER SEAT....................8N-16
SWITCH - DIAGNOSIS AND TESTING,
POWER LOCK........................8N-4
SWITCH - DIAGNOSIS AND TESTING,
POWER MIRROR....................8N-12
SWITCH - DIAGNOSIS AND TESTING,
SEAT BELT .........................8O-51
SWITCH - DIAGNOSIS AND TESTING,
WINDOW...........................8N-20
SWITCH - INSTALLATION...............8P-8
SWITCH - INSTALLATION, ADJUSTABLE
PEDAL...............................5-6
SWITCH - INSTALLATION, BRAKE LAMP . . 8L-11
SWITCH - INSTALLATION, DRIVER SEAT . . . 8N-15
SWITCH - INSTALLATION, HEADLAMP....8L-15
SWITCH - INSTALLATION, HEATED SEAT . . 8G-13
SWITCH - INSTALLATION, IGNITION......19-11
SWITCH - INSTALLATION, MULTI-
FUNCTION..........................8L-19
SWITCH - INSTALLATION, OIL
PRESSURE.........................9-294
SWITCH - INSTALLATION, PASSENGER
AIRBAG ON/OFF.....................8O-44
SWITCH - INSTALLATION, PASSENGER
SEAT ..............................8N-16
SWITCH - INSTALLATION, POWER LOCK . . . 8N-4
SWITCH - INSTALLATION, TOW/HAUL
OVERDRIVE..................21-262,21-393
SWITCH - INSTALLATION, WASHER
FLUID LEVEL........................8R-11
SWITCH - INSTALLATION, WINDOW.....8N-21
SWITCH - OPERATION.................8P-7
SWITCH - OPERATION, BACKUP LAMP....8L-8
SWITCH - OPERATION, BLOWER MOTOR . . 24-20
SWITCH - OPERATION, BRAKE LAMP......8L-9
SWITCH - OPERATION, CLUTCH PEDAL
POSITION...........................6-13
SWITCH - OPERATION, DOOR AJAR......8L-27
SWITCH - OPERATION, DRIVER SEAT....8N-14
SWITCH - OPERATION, HAZARD.........8L-14
SWITCH - OPERATION, HEADLAMP......8L-14
SWITCH - OPERATION, HEATED SEAT....8G-12
SWITCH - OPERATION, IGNITION.........19-9
SWITCH - OPERATION, LUMBAR
CONTROL..........................8N-18
SWITCH - OPERATION, PASSENGER
AIRBAG ON/OFF.....................8O-43
SWITCH - OPERATION, PASSENGER
SEAT ..............................8N-15
SWITCH - OPERATION, POWER
STEERING PRESSURE.................19-46
SWITCH - OPERATION, PTO.......14-36,14-85
SWITCH - OPERATION, REAR WINDOW
DEFOGGER..........................8G-4
SWITCH - OPERATION, SEAT BELT.......8O-51
SWITCH - OPERATION, SELECTOR.....21-510,
21-540,21-574
SWITCH - OPERATION, TOW/HAUL
OVERDRIVE..................21-262,21-392
SWITCH - OPERATION, WASHER FLUID
LEVEL..............................8R-9
SWITCH - REMOVAL...................8P-8
SWITCH - REMOVAL, ADJUSTABLE
PEDAL...............................5-6
SWITCH - REMOVAL, BRAKE LAMP
......8L-10
SWITCH - REMOVAL, DRIVER SEAT
......8N-15
SWITCH - REMOVAL, HEADLAMP
........8L-14
SWITCH - REMOVAL, HEATED SEAT
......8G-13
SWITCH - REMOVAL, IGNITION
.........19-10SWITCH - REMOVAL, LUMBAR
CONTROL..........................8N-18
SWITCH - REMOVAL, MULTI-FUNCTION . . . 8L-19
SWITCH - REMOVAL, OIL PRESSURE.....9-294
SWITCH - REMOVAL, PASSENGER
AIRBAG ON/OFF.....................8O-43
SWITCH - REMOVAL, PASSENGER SEAT . . 8N-16
SWITCH - REMOVAL, POWER LOCK......8N-4
SWITCH - REMOVAL, POWER MIRROR . . . 8N-12
SWITCH - REMOVAL, TOW/HAUL
OVERDRIVE..................21-262,21-392
SWITCH - REMOVAL, WASHER FLUID
LEVEL.............................8R-10
SWITCH - REMOVAL, WINDOW.........8N-20
SWITCH AND KEY LOCK CYLINDER -
DIAGNOSIS AND TESTING, IGNITION.....19-11
SWITCH BEZEL - INSTALLATION,
INSTRUMENT PANEL HEADLAMP........23-56
SWITCH BEZEL - REMOVAL,
INSTRUMENT PANEL HEADLAMP........23-56
SWITCH OPERATING MODES,
STANDARD PROCEDURE -
CONFIGURING A NEW MODULE..........8Q-3
SWITCH VALVE - DESCRIPTION,
SOLENOID.........................21-398
SWITCH VALVE - OPERATION, SOLENOID . 21-398
SWITCHES - DESCRIPTION, REMOTE.....8A-10
SWITCHES - DIAGNOSIS AND TESTING,
REMOTE...........................8A-11
SWITCHES - INSTALLATION, REMOTE....8A-12
SWITCHES - OPERATION, REMOTE........8A-11
SWITCHES - REMOVAL, REMOTE........8A-12
SYMBOLS - DESCRIPTION,
INTERNATIONAL....................Intro.-5
TACHOMETER - DESCRIPTION..........8J-38
TACHOMETER - OPERATION............8J-38
TAILGATE - INSTALLATION.............23-17
TAILGATE - REMOVAL.................23-17
TAILGATE MARKER LAMP -
INSTALLATION.......................8L-18
TAILGATE MARKER LAMP - REMOVAL....8L-18
TAILPIPE - 5.9L DIESEL - INSPECTION....11-10
TAILPIPE - 5.9L DIESEL - INSTALLATION . . 11-11
TAILPIPE - 5.9L DIESEL - REMOVAL.....11-10
TAILPIPE - INSPECTION...............11-11
TAILPIPE - INSTALLATION..............11-11
TAILPIPE - REMOVAL.................11-11
TANK - DESCRIPTION, FUEL............14-17
TANK - OPERATION, FUEL..............14-17
TANK MODULE - DESCRIPTION, FUEL....14-63
TANK MODULE - INSTALLATION, FUEL....14-64
TANK MODULE - OPERATION, FUEL......14-63
TANK MODULE - REMOVAL, FUEL.......14-63
TAPPETS - DIAGNOSIS AND TESTING,
HYDRAULIC.........................9-210
TAPPETS - INSTALLATION, HYDRAULIC . . . 9-211
TAPPETS - REMOVAL, HYDRAULIC.......9-211
TASK MANAGER - DESCRIPTION.........25-1
TASK MANAGER - OPERATION...........25-5
TCM QUICK LEARN - STANDARD
PROCEDURE........................8E-23
TEMP INDICATOR - DESCRIPTION,
TRANS.............................8J-40
TEMP INDICATOR - OPERATION, TRANS
. . 8J-40
TEMP SENSOR - DESCRIPTION,
AMBIENT
..........................8M-10
TEMP SENSOR - OPERATION, AMBIENT
. . 8M-10
TEMPERATURE GAUGE - DESCRIPTION,
ENGINE
............................8J-24
TEMPERATURE GAUGE - OPERATION,
ENGINE
............................8J-24
TEMPERATURE SENSOR - DESCRIPTION,
BATTERY
...........................8F-21
TEMPERATURE SENSOR - DESCRIPTION,
ENGINE COOLANT
.....................7-38
TEMPERATURE SENSOR - DESCRIPTION,
EVAPORATOR
.......................24-22
TEMPERATURE SENSOR - DESCRIPTION,
INTAKE AIR
.........................14-30
TEMPERATURE SENSOR - DESCRIPTION,
TRANSMISSION
...............21-267,21-408
TEMPERATURE SENSOR - DIAGNOSIS
AND TESTING, AMBIENT
..............8M-10
TEMPERATURE SENSOR -
INSTALLATION, BATTERY
..............8F-21
TEMPERATURE SENSOR -
INSTALLATION, ENGINE COOLANT
........7-41
32 INDEXDR
Description Group-Page Description Group-Page Description Group-Page