
GENERAL INFORMATION
INTRODUCTION
Both the heater and the heater/air conditioning
systems share many of the same components. This
group will deal with both systems together when
component function is common, and separately when
they are not.
For proper operation of the instrument panel con-
trols, refer to the Owner's Manual provided with the
vehicle.
All vehicles are equipped with a common A/C-
heater unit housing assembly. When the vehicle has
only a heater system, the evaporator and recirculat-
ing air door are omitted.
An optional zone control HVAC unit is available.
This unit has dual blend-air doors that can be regu-
lated independently of each other. The temperature
setting can be different from driver's side to passen-
ger side. There is also a rear (aux.) heating and A/C
system available when the vehicle is equipped with
zone control.
SAFETY PRECAUTIONS AND WARNINGS
WARNING: WEAR EYE PROTECTION WHEN SER-
VICING THE AIR CONDITIONING REFRIGERANT
SYSTEM. SERIOUS EYE INJURY CAN RESULT
FROM EYE CONTACT WITH REFRIGERANT. IF EYE
CONTACT IS MADE, SEEK MEDICAL ATTENTION
IMMEDIATELY.
DO NOT EXPOSE REFRIGERANT TO OPEN
FLAME. POISONOUS GAS IS CREATED WHEN
REFRIGERANT IS BURNED. AN ELECTRONIC TYPE
LEAK DETECTOR IS RECOMMENDED.
LARGE AMOUNTS OF REFRIGERANT RELEASED
IN A CLOSED WORK AREA WILL DISPLACE THE
OXYGEN AND CAUSE SUFFOCATION.
THE EVAPORATION RATE OF REFRIGERANT AT
AVERAGE TEMPERATURE AND ALTITUDE IS
EXTREMELY HIGH. AS A RESULT, ANYTHING THAT
COMES IN CONTACT WITH THE REFRIGERANT
WILL FREEZE. ALWAYS PROTECT SKIN OR DELI-
CATE OBJECTS FROM DIRECT CONTACT WITH
REFRIGERANT. R-134a SERVICE EQUIPMENT OR
VEHICLE A/C SYSTEM SHOULD NOT BE PRES-
SURE TESTED OR LEAK TESTED WITH COM-
PRESSED AIR.
SOME MIXTURES OF AIR and R-134a HAVE BEEN
SHOWN TO BE COMBUSTIBLE AT ELEVATED
PRESSURES. THESE MIXTURES ARE POTENTIALLY
DANGEROUS AND MAY RESULT IN FIRE OR
EXPLOSION CAUSING INJURY OR PROPERTY
DAMAGE.
ANTIFREEZE IS AN ETHYLENE GLYCOL BASE
COOLANT AND IS HARMFUL IF SWALLOWED ORINHALED. SEEK MEDICAL ATTENTION IMMEDI-
ATELY IF SWALLOWED OR INHALED. DO NOT
STORE IN OPEN OR UNMARKED CONTAINERS.
WASH SKIN AND CLOTHING THOROUGHLY AFTER
COMING IN CONTACT WITH ETHYLENE GLYCOL.
KEEP OUT OF REACH OF CHILDREN AND PETS.
DO NOT OPEN A COOLING SYSTEM WHEN THE
ENGINE IS AT RUNNING TEMPERATURE. PER-
SONAL INJURY CAN RESULT.
CAUTION: The engine cooling system is designed
to develop internal pressure of 97 to 123 kPa (14 to
18 psi). Allow the vehicle to cool a minimum of 15
minutes before opening the cooling system. Refer
to Group 7, Cooling System.
DESCRIPTION AND OPERATION
AIR DISTRIBUTION DUCTS
The air distribution ducts for the A/C, Heater,
Defroster, and Second Seating Air Distribution are
not serviceable in vehicle. The procedures for service
of these ducts are covered in Group 8E, Instrument
Panel and Gauges.
The only ducts that are serviceable in the vehicle
are the side window demister ducts and the ducts
that feed the front door outlets for the first rear pas-
senger(s) seating. To service the door ducts refer to
Group 23, Body.
A/C PRESSURE TRANSDUCER
The A/C Pressure Transducer (Fig. 1) monitors the
refrigerant gas pressure on the high side of the sys-
tem. The transducer is located on the liquid line. The
pressure transducer turns off the voltage to the com-
pressor clutch coil when refrigerant gas pressure
drops to levels that could damage the compressor.
The transducer also is used to adjust condenser fan
speeds and will turn off compressor at high refriger-
ant pressures. The pressure transducer is a sealed
factory calibrated unit. It must be replaced if defec-
tive. O-ring replacement is required whenever the
pressure transducer is serviced. Be sure to use the
O-ring specified for the transducer.
A/C SERVICE PORTS
The A/C service port valve cores are located within
the A/C lines (Fig. 2). The High Side (Discharge)
valve service port is located on the liquid line near
the right frame rail. The Low Side (Suction) valve
service port is located on the suction line near the
compressor.
24 - 2 HEATING AND AIR CONDITIONINGNS

CAUTION: The refrigerant oil used in a R-134a A/C
system is unique. Use only oils which were
designed to work with R-134a refrigerant. The oil
designated for this vehicle is ND8 PAG (polyalka-
lene glycol).
SERVICING REFRIGERANT OIL LEVEL
(1) Using a refrigerant recovery machine, remove
refrigerant from the A/C system.
(2) Remove refrigerant lines from A/C compressor.
(3) Remove compressor from vehicle.
(4) From suction port on top of compressor, drain
refrigerant oil from compressor.
(5) Add system capacity minus the capacity of
components that have not been replaced through suc-
tion port on compressor. Refer to the Refrigerant Oil
Capacity Chart.
(6) Install compressor, connect refrigerant lines,
evacuate, and charge refrigerant system.
DIAGNOSIS AND TESTING
ACTUATOR CALIBRATION/DIAGNOSTICS AND
COOLDOWN TEST
GENERAL INFORMATION
If the HVAC control module is replaced, the Cali-
bration Diagnostic and Cooldown tests will need to
be performed. Once this group of tests have success-
fully passed, they can be performed individually. The
engine must be running during the test to provide
hot coolant for the heater, A/C compressor operation
and to assure that the actuators are calibrated cor-
rectly. The HVAC control module is capable of trou-
bleshooting the system in approximately 120 seconds.
If a condition is detected, an error code is displayed.
The error code cannot be erased until the condition is
repaired and the diagnostic test is performed. Check
wire before replacing components, refer to Group 8W,
Wiring Diagrams.CAUTION: Do not remove the actuators from the
Heater-A/C unit assembly with power applied.
Removal should only be done with the Ignition OFF.
The actuators have no mechanical stops to limit the
travel. If the actuator rotates and is not connected
to the unit assembly, it will become out of calibra-
tion.
ACTUATOR CALIBRATION
Mode, Blend and Zone (if equipped) door calibra-
tion compensates for mechanical variations in the
actuators, HVAC control module and its linkages. In-
vehicle calibration can be entered from the control's
front panel. If the REAR WIPE and INTERMIT-
TENT LED's flash simultaneously when Ignition is
cycled ON, the actuators have not been calibrated or
during the previous calibration a failure occurred
(Fig. 6) and (Fig. 7). Diagnostics will always occur
during Calibration Diagnostic and Cooldown test.
REFRIGERANT OIL CAPACITIES
Refrigerant
Oil Capaci-
tiesFront A/C Dual A/C
Component ml oz ml oz
Compressor 150 ml 5.0 oz 220 ml 7.4 oz
Filter-Drier 30 ml 1.0 oz 30 ml 1.0 oz
Condenser 30 ml 1.0 oz 30 ml 1.0 oz
Evaporator 60 ml 2.0 oz 60 ml 2 .0 oz
Rear Evap. N/A N/A 60 ml 2.0 oz
Fig. 6 Radio Bezel and HVAC Control
24 - 6 HEATING AND AIR CONDITIONINGNS
DESCRIPTION AND OPERATION (Continued)

be 21ÉC to 27ÉC (70ÉF to 85ÉF). To test the expansion
valve:
NOTE: Liquid CO2 is required to test the expansion
valve. It is available from most welding supply facil-
ities. CO2 is also available from companies which
service and sell fire extinguishers.
(1) Connect a charging station or manifold gauge
set to the refrigerant system service ports. Verify the
refrigerant charge level.
(2) Close all doors, windows and vents to the pas-
senger compartment.
(3) Set heater A/C control to A/C, full heat,
FLOOR, and high blower.
(4) Start the engine and allow to idle (1000 rpm).
After the engine has reached running temperature,
allow the passenger compartment to heat up. This
will create the need for maximum refrigerant flow
into the evaporator.
(5) If the refrigerant charge is sufficient, discharge
(high pressure) gauge should read 965 to 1655 kPa
(140 to 240 psi). Suction (low pressure) gauge should
read 140 kPa to 207 kPa (20 psi to 30 psig). If system
cannot achieve proper pressure readings, replace the
expansion valve. If pressure is correct, proceed with
test.
WARNING: PROTECT SKIN AND EYES FROM CON-
TACTING CO2 PERSONAL INJURY CAN RESULT.
(6) If suction side low pressure is within specified
range, freeze the expansion valve control head for 30
seconds. Use a super cold substance (liquid CO2).Do
not spray R-134a or R-12 Refrigerant on the
expansion valve for this test.Suction side low
pressure should drop by 10 psi. If not, replace expan-
sion valve.
(7) Allow expansion valve to thaw. The low pres-
sure gauge reading should stabilize at 140 kPa to
240 kPa (20 psi to 30 psig). If not, replace expansion
valve.
(8) When expansion valve test is complete, test
A/C overall performance. Remove all test equipment
before returning vehicle to use.
HEATER PERFORMANCE TEST
PRE-DIAGNOSTIC PREPARATIONS
Review Safety Precautions and Warnings in this
group before performing the following procedures.
Check the coolant level, drive belt tension, vacuum
line connections, radiator air flow and fan operation.
Start engine and allow to warm up to normal tem-
perature.WARNING: DO NOT REMOVE RADIATOR CAP
WHEN ENGINE IS HOT, PERSONAL INJURY CAN
RESULT.
If vehicle has been run recently, wait 15 minutes
before removing cap. Place a rag over the cap and
turn it to the first safety stop. Allow pressure to
escape through the overflow tube. When the system
stabilizes, remove the cap completely.
MAXIMUM HEATER OUTPUT: TEST AND
ACTION
Engine coolant is provided to the heater system by
two 16 mm (5/8 inch inside diameter) heater hoses.
With engine idling at normal running temperature,
set the control to maximum heat, floor, and high
blower setting. Using a test thermometer, check the
air temperature coming from the floor outlets, refer
to Temperature Reference Table.
If the floor outlet air temperature is insufficient,
refer to Group 7, Cooling Systems for specifications.
Both heater hoses should be HOT to the touch (cool-
ant return hose should be slightly cooler than the
supply hose). If coolant return hose is much cooler
than the supply hose, locate and repair engine cool-
ant flow obstruction in heater system.
POSSIBLE LOCATIONS OR CAUSE OF
OBSTRUCTED COOLANT FLOW
(1) Pinched or kinked heater hoses.
(2) Improper heater hose routing.
(3) Plugged heater hoses or supply and return
ports at cooling system connections, refer to Group 7,
Cooling System.
(4) Plugged heater core.
(5) Air locked heater core.
(6) If coolant flow is verified and outlet tempera-
ture is insufficient, a mechanical problem may exist.
POSSIBLE LOCATION OR CAUSE OF
INSUFFICIENT HEAT
(1) Obstructed cowl air intake.
(2) Obstructed heater system outlets.
(3) Blend-air door not functioning properly.
TEMPERATURE REFERENCE TABLE
AMBIENT
TEMPERATUREMINIMUM FLOOR
OUTLET TEMPERATURE
CELSIUS FAHRENHEIT CELSIUS FAHRENHEIT
15.5É 60É 62.2É 144É
21.1É 70É 63.8É 147É
26.6É 80É 65.5É 150É
32.2É 90É 67.2É 153É
NSHEATING AND AIR CONDITIONING 24 - 15
DIAGNOSIS AND TESTING (Continued)

TEMPERATURE CONTROL
If temperature cannot be adjusted with the TEMP
lever on the control panel, the following could require
service:
(1) Blend-air door binding.
(2) Faulty blend-air door motor.
(3) Improper engine coolant temperature.
(4) Faulty Instrument Panel Control.
SYSTEM CHARGE LEVEL TEST
The procedure below should be used to check
and/or fill the refrigerant charge in the air condition-
ing system.
NOTE: The amount of R134a refrigerant that the air
conditioning system holds is:
²Without rear A/C± .96 kg (34 oz. or 2.13 lbs.)
²With Rear A/C± 1.36 kg (48 oz. or 3.00 lbs.)
NOTE: Low Charge, condition may be described
as:
²Loss of A/C performance
²Fog from A/C outlets
²evaporator may have a HISS sound
There are two different ways the system can be
tested:
²With a scan tool (DRB), thermocouple and the
Charge Determination Graph. Use the scan tool
(DRB) diagnostic topic: Engine±System Monitors, A/C
Pressure.
²Using a manifold gauge set, a thermocouple and
the Charge Determination Graph.
It is recommended to use the gauges or reclaim/re-
cycle equipment.
WARNING: AVOID BREATHING A/C REFRIGERANT
AND LUBRICANT VAPOR OR MIST. EXPOSURE MAY
IRRITATE EYES, NOSE AND THROAT. USE ONLY
APPROVED SERVICE EQUIPMENT MEETING SAE
REQUIREMENTS TO DISCHARGE R-134a SYSTEM.
IF ACCIDENTAL SYSTEM DISCHARGE OCCURS,
VENTILATE WORK AREA BEFORE RESUMING SER-
VICE.
R-134a SERVICE EQUIPMENT OR VEHICLE A/C
SYSTEM SHOULD NOT BE PRESSURE TESTED OR
LEAK TESTED WITH COMPRESSED AIR. SOME
MIXTURES OF AIR/R-134a HAVE BEEN SHOWN TO
BE COMBUSTIBLE AT ELEVATED PRESSURES.
THESE MIXTURES ARE POTENTIALLY DANGER-
OUS AND MAY RESULT IN FIRE OR EXPLOSION
CAUSING INJURY OR PROPERTY DAMAGE.
(1) Establish your preferred method of measuring
liquid line pressure. Use a manifold gauge set or a
DRB scan tool.(2) Attach a clamp-on thermocouple (P.S.E. 66-324-
0014 or 80PK-1A) or equivalent to the liquid line. It
must be placed as close to the A/C Pressure Trans-
ducer as possible to observe liquid line temperature.
Refer to ªThermocouple Probeº in this section for
more information on probe.
(3) The vehicle must be in the following modes:
²Transaxle in Park
²Engine Idling at 700 rpm
²A/C Controls Set to Outside Air
²Panel Mode
²Full Cool
²High Blower motor, (vehicle equipped with rear
A/C turn rear blower motor ON HIGH)
²A/C Button in the ON position
²Vehicle Windows Open.
²Recirc. button turned OFF
(4) Operate system for a couple of minutes to allow
the system to stabilize.
(5) Set system pressure to about 1793 kPa (260
psi) by placing a piece of cardboard over part of the
front side of the condenser. To place cardboard prop-
erly, remove the upper radiator-condenser cover.
Insert cardboard between condenser and radiator
front. This will maintain a constant pressure.
(6) Observe Liquid Line pressure and Liquid line
temperature. Using theCharge Determination
Chartdetermine where the system is currently oper-
ating. If the system is in the undercharged region,
ADD 0.057 Kg. (2 oz.) to the system and recheck
readings. If the system is in the overcharged region,
RECLAIM 0.057 Kg. (2 oz.) from the system and
recheck readings. Continue this process until the sys-
tem readings are in the proper charge area on the
Charge Determination Chart.
(7) The same procedure can be performed using
the scan tool (DRB). To determine liquid line pres-
sure, attach the scan tool, go to System Moni-
tors±A/C Pressure. Observe liquid line pressure from
A/C Pressure Transducer on digital display and digi-
tal thermometer. Refer toCharge Determination
Chartand determine where the system is operating.
SERVICE PROCEDURES
R-134a REFRIGERANT
This vehicle uses a new type of refrigerant called
R-134a. It is a non-toxic, non-flammable, clear color-
less liquefied gas.
R-134a refrigerant is not compatible with R-12
refrigerant in an air conditioning system. Even a
small amount of R-12 in a R-134a system could cause
compressor failure, refrigerant oil to sludge and/or
poor performance.Never add any other type of
refrigerant to a system designed to use R-134a
refrigerant. System failure will occur.
24 - 16 HEATING AND AIR CONDITIONINGNS
DIAGNOSIS AND TESTING (Continued)

COMPRESSOR
REMOVAL
WARNING: REFER TO REFRIGERANT SERVICE
PROCEDURES FOR INFORMATION REGARDING
PROPER RECOVERY OF THE REFRIGERANT
BEFORE ATTEMPTING TO REMOVE THE COM-
PRESSOR.
(1) Disconnect negative battery cable.
(2) Pinch off coolant lines to rear Heat unit (if
equipped). Drain engine coolant.
(3) Remove upper radiator hose.
(4) Remove drive belt (refer to Group 7, Cooling
System). Disconnect compressor clutch wire lead.
(5) Remove refrigerant lines from compressor (Fig.
21) and (Fig. 22).
(6) Remove compressor nuts and bolts (Fig. 23).
(7) Remove compressor (Fig. 24).
INSTALLATION
For installation, reverse the above procedures.
COMPRESSOR CLUTCH/COIL
REMOVAL
(1) Remove the compressor shaft bolt (Fig. 25). A
band type oil filter removal tool can be placed around
the clutch plate to aid in bolt removal.
Fig. 21 Suction Line
Fig. 22 Discharge line
Fig. 23 Compressor Mounts
Fig. 24 Compressor Removal
NSHEATING AND AIR CONDITIONING 24 - 23
REMOVAL AND INSTALLATION (Continued)

(2) Remove liquid line at filter-drier (Fig. 42).
(3) Remove the (2) bolts holding filter-drier bracket
to radiator fan module bracket.
(4) Remove the lower liquid line at condenser.
(5) Remove the upper radiator crossmember.
(6) Pull up on radiator and slide filter-drier from
the mounting location.
INSTALLATION
(1) Before installation, replace both refrigerant
line O-rings. Then reverse the above procedures.
Torque filter/drier mounting bolts to 45 in. lbs.610.
(2) Evacuate and recharge system.
HEATER A/C UNIT HOUSING
REMOVAL
WARNING: IF EQUIPPED WITH AIR CONDITIONING,
THE REFRIGERATION SYSTEM MUST BE COM-
PLETELY EMPTY BEFORE PROCEEDING.
(1) Set parking brake.
(2) Disconnect battery negative cable.
(3) Using a refrigerant recovery machine, remove
refrigerant from the A/C system (Fig. 43).
(4) Remove wiper module. Refer to Group 8K,
Windshield Wipers and Washers.
(5) Pinch off rear heater lines if equipped.
(6) Drain engine coolant. Remove heater hoses at
the heater core (Fig. 44). Plug coolant lines.
(7) Remove suction and liquid lines at the expan-
sion valve (Fig. 45).(8) Remove the Instrument Panel Assembly. Refer
to Group 8E, Instrument Panel and Gauges.
(9) Remove heater ducts.
Fig. 42 Filter-Drier Assembly
Fig. 43 A/C Service Ports
Fig. 44 Heater Hoses
Fig. 45 Expansion Valve Plate
NSHEATING AND AIR CONDITIONING 24 - 29
REMOVAL AND INSTALLATION (Continued)

(10) Disconnect the two upper mounts from the
upper reinforcement and the lower mount from the
tunnel.
(11) Remove the (3) nuts (in the engine compart-
ment) securing the unit to the dash panel (Fig. 46).
(12) Disconnect the HVAC housing wiring harness.
(13) Pull the entire unit rearward until the studs
on the unit clear the dash panel. Drop the unit down.
Pull it rearward to remove it from vehicle.
INSTALLATION
(1) For installation of the assembly, reverse the
above procedures. Install new O-rings on plumbing
inlets
(2) Evacuate and recharge the A/C system.
(3) Perform HVAC control Calibration Diagnostic
and Cooldown test.
HEATER CORE
REMOVAL
(1) Drain coolant system.
(2) Remove left side lower column cover.
(3) Remove steering column assembly. Refer to
Group 19, Steering for service procedure.
(4) Remove ABS module, bracket and wiring (Fig.
47).
(5) Remove I/P to body harness interconnect and
bracket (Fig. 48).
(6) Remove lower silencer boot at base of steering
shaft (Fig. 49)
(7) Pinch off heater lines under the hood.
(8) Remove heater core cover. Insert a small
amount of towels under the heater core tubes.
Remove heater core plate and tubes (Fig. 50).
(9) Depress heater core retaining clips (Fig. 51).
(10) Pull up on accelerator pedal and slide heater
core past (Fig. 52).(11) Depress brake pedal (Fig. 53) and remove
heater core from HVAC housing.
Fig. 46 HVAC Bolt-Up
Fig. 47 ABS MODULE
Fig. 48 Interconnect And Bracket
Fig. 49 Lower Silencer Boot
24 - 30 HEATING AND AIR CONDITIONINGNS
REMOVAL AND INSTALLATION (Continued)

CAUTION: When removing hoses from heater core
inlet or outlet nipples, do not use excessive force.
Heater core may become damaged and leak engine
coolant.
(3) Carefully rotate hose back and forth while tug-
ging slightly away from connector nipple. If the hose
will not come off, slice the hose at the connector nip-
ple and peel off heater hose. This method will require
heater hose replacement.
INSTALLATION
For installation, reverse the above procedures.
LIQUID LINE
REMOVAL
(1) Disconnect the battery negative cable.
(2) Recover A/C system refrigerant.
(3) Remove the accessory drive belt.
(4) Remove upper generator bracket.
(5) Remove ground wire at dash panel.
(6) Remove the nut retaining the refrigerant line
sealing plate to the expansion valve (Fig. 39).
(7) Remove the stud from the expansion valve (Fig.
40).
(8) Remove liquid line from expansion valve.
(9) Cover the openings to prevent contamination.
(10) Disconnect wire connector at pressure trans-
ducer.
(11) Remove liquid line mounting bracket at right
frame rail.
(12) Using access slot between radiator crossmem-
ber and grille, loosen liquid line mounting plate at
filter-drier. Remove liquid line from filter-drier. It
may be necessary to bend liquid line in half to
remove line. The replacement line is a two-piece
assembly.
(13) Remove the old O-rings.
INSTALLATION
For installation, reverse the above procedures.
²Install the stud to the evaporator sealing plate
and tighten 7 to 11 N´m (64 to 96 in. lbs.) torque.
²Install new O-rings.
²Install two-piece line in place of original part.
²A
ssemble line halves after it is installed on vehicle.²Evacuate and recharge A/C system.
MODE DOOR ACTUATOR
REMOVAL
(1) Remove the lower left side steering column
cover. Refer to Group 8E, Instrument Panel and Sys-
tems.
(2) Remove ABS control module (Fig. 56).
(3) Remove mode actuator connector (Fig. 57).
(4) Remove mode door actuator (Fig. 58).
INSTALLATION
(1) For installation, reverse the above procedures.
Fig. 55 Lower Heater Hose
Fig. 56 ABS Control Module
Fig. 57 Mode Door Actuator Connector
24 - 32 HEATING AND AIR CONDITIONINGNS
REMOVAL AND INSTALLATION (Continued)