Page 1817 of 1938

HEATING AND AIR CONDITIONING
CONTENTS
page page
FRONT HEATING AND AIR CONDITIONING
SYSTEM............................... 1REAR HEATING AND AIR CONDITIONING
SYSTEM.............................. 41
FRONT HEATING AND AIR CONDITIONING SYSTEM
INDEX
page page
GENERAL INFORMATION
INTRODUCTION......................... 2
SAFETY PRECAUTIONS AND WARNINGS...... 2
DESCRIPTION AND OPERATION
A/C PRESSURE TRANSDUCER.............. 2
A/C SERVICE PORTS..................... 2
AIR DISTRIBUTION DUCTS................. 2
COMPRESSOR HIGH-PRESSURE RELIEF
VALVE................................ 3
CONDENSATE DRAIN..................... 3
ENGINE COOLING SYSTEM REQUIREMENTS . . 3
EVAPORATOR PROBE..................... 3
HANDLING TUBING AND FITTINGS........... 3
HVAC CONTROL MODULE................. 4
REAR BLOWER SPEED SWITCH............ 3
SIDE DOOR HEATER A/C OUTLETS.......... 4
SIDE WINDOW DEMISTER................. 4
SYSTEM AIRFLOW....................... 4
SYSTEM OIL LEVEL...................... 5
DIAGNOSIS AND TESTING
A/C PERFORMANCE TEST................ 12
A/C PRESSURE TRANSDUCER............. 12
ACTUATOR CALIBRATION/DIAGNOSTICS AND
COOLDOWN TEST...................... 6
BLOWER MOTOR AND WHEEL ASSEMBLY.... 13
COMPRESSOR CLUTCH/COIL.............. 13
COMPRESSOR NOISE DIAGNOSIS.......... 13
EXPANSION VALVE...................... 13
HEATER PERFORMANCE TEST............ 15
HVAC CONTROL DIAGNOSTIC CONDITIONS . . . 9
SYSTEM CHARGE LEVEL TEST............ 16SERVICE PROCEDURES
CHARGING REFRIGERANT SYSTEM........ 17
EVACUATING REFRIGERANT SYSTEM....... 18
R-134a REFRIGERANT................... 16
STICKING HVAC CONTROL MODULE PUSH
BUTTONS............................ 19
SYSTEM LEAK CHECKING................ 19
THERMOCOUPLE PROBE................. 19
REMOVAL AND INSTALLATION
A/C PRESSURE TRANSDUCER............. 20
A/C SERVICE PORTS.................... 20
BLEND-AIR DOOR ACTUATOR............. 20
BLOWER MOTOR AND WHEEL ASSEMBLY.... 21
BLOWER MOTOR RESISTOR BLOCK........ 21
BLOWER MOTOR WHEEL................. 22
COMPRESSOR CLUTCH/COIL.............. 23
COMPRESSOR......................... 23
CONDENSER ASSEMBLY................. 25
DISCHARGE LINE....................... 26
EVAPORATOR PROBE.................... 27
EXPANSION VALVE...................... 28
FILTER-DRIER ASSEMBLY................. 28
HEATER A/C UNIT HOUSING............... 29
HEATER CORE......................... 30
HEATER HOSES........................ 31
LIQUID LINE........................... 32
MODE DOOR ACTUATOR................. 32
RECIRC DOOR ACTUATOR................ 34
SIDE WINDOW DEMISTER DUCTS.......... 33
SUCTION LINE.......................... 33
DISASSEMBLY AND ASSEMBLY
HEATER A/C UNIT RECONDITION........... 34
NSHEATING AND AIR CONDITIONING 24 - 1
Page 1818 of 1938

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
Page 1819 of 1938

The High Side service port is a two piece port and
is serviceable. The Low Side service port is not ser-
viceable, the suction line would have to be replaced.
REAR BLOWER SPEED SWITCH
The rear blower speed switch controls the rear
blower with the choice of low and high speeds. When
the switch is on it allows the blower speed switch
located on the rear headliner to control rear blower
speed. This switch will override the rear headliner
blower switch. For operation instructions refer to the
Owner's Manual. The rear blower speed switch is
serviced separately from the A/C control module. For
service procedures, refer to Group 8E, Instrument
Panel And Gauges.
COMPRESSOR HIGH-PRESSURE RELIEF VALVE
The High Pressure Relief Valve prevents damage
to the air conditioning system if excessive pressure
develops. Excessive pressure can be caused by con-
denser air flow blockage, refrigerant overcharge, or
air and moisture in the system.The high pressure relief valve vents only a small
amount of refrigerant necessary to reduce system
pressure and then reseats itself. The majority of the
refrigerant is conserved in the system. The valve is
calibrated to vent at a pressure of 3450 to 4140 kPa
(500 to 600 psi). If a valve has vented a small
amount of refrigerant, it does not necessarily mean
the valve is defective.
The High Pressure Relief Valve is located on the
compressor manifold at the discharge passage.
NOTE: Special effort must be used to keep all
R-134a system components moisture-free. Moisture
in the oil is very difficult to remove and will cause a
reliability problem with the compressor.
CONDENSATE DRAIN
Condensation from the evaporator housing is
drained through the dash panel and on to the
ground. This drain must be kept open to prevent
water from collecting in the bottom of the housing.
If the drain is blocked condensate cannot drain,
causing water to back up and spill into the passenger
compartment. It is normal to see condensate drain-
age below the vehicle.
ENGINE COOLING SYSTEM REQUIREMENTS
To maintain ample temperature levels from the
heating-A/C system, the cooling system must be in
proper working order. Refer to Group 0, Lubrication
and Maintenance or Group 7, Cooling System of this
manual.
The use of a bug screen is not recommended. Any
obstructions forward of the condenser can reduce the
effectiveness of the air conditioning system.
EVAPORATOR PROBE
The Evaporator probe is located on the HVAC. The
probe prevents evaporator freeze-up by signaling the
Powertrain Control Module to cycle the compressor
ON and OFF. The probe monitors the temperature of
the refrigerant after expansion.
The evaporator probe is inserted into the evapora-
tor between the coils. The probe is a sealed unit and
cannot be adjusted or repaired. It must be replaced if
found defective.
HANDLING TUBING AND FITTINGS
Kinks in the refrigerant tubing or sharp bends in
the refrigerant hose lines will greatly reduce the
capacity of the entire system. High pressures are pro-
duced in the system when it is operating. Extreme
care must be exercised to make sure that all connec-
tions are pressure tight. Dirt and moisture can enter
the system when it is opened for repair or replace-
ment of lines or components. The refrigerant oil will
Fig. 1 A/C Pressure Transducer
Fig. 2 Valve Service Ports
NSHEATING AND AIR CONDITIONING 24 - 3
DESCRIPTION AND OPERATION (Continued)
Page 1820 of 1938

absorb moisture readily out of the air. This moisture
will convert into acids within a closed system.
CAUTION: The system must be completely empty
before opening any fitting or connection in the
refrigeration system. Open fittings with caution
even after the system has been emptied. If any
pressure is noticed as a fitting is loosened,
retighten fitting and evacuate the system again.
A good rule for the flexible hose lines is to keep
the radius of all bends at least 10 times the diame-
ter of the hose. Sharper bends will reduce the flow
of refrigerant. The flexible hose lines should be
routed so they are at least 3 inches (80 mm) from
the exhaust manifold. Inspect all flexible hose lines
to make sure they are in good condition and prop-
erly routed.
The use of correct wrenches when making con-
nections is very important. Improper wrenches or
improper use of wrenches can damage the fittings.
The internal parts of the A/C system will remain
stable as long as moisture-free refrigerant and
refrigerant oil is used. Abnormal amounts of dirt,
moisture or air can upset the chemical stability.
This may cause operational troubles or even seri-
ous damage if present in more than very small
quantities.
When opening a refrigeration system, have every-
thing you will need to repair the system ready. This
will minimize the amount of time the system must
be opened. Cap or plug all lines and fittings as
soon as they are opened. This will help prevent the
entrance of dirt and moisture. All new lines and
components should be capped or sealed until they
are ready to be used.
All tools, including the refrigerant dispensing
manifold, the manifold gauge set, and test hoses
should be kept clean and dry.
HVAC CONTROL MODULE
The HVAC control module regulates the operation
of the various actuator motors. The actuator motors
are used to move the mode, blend- air, and RECIRC.
doors (Fig. 3).
The control module is included in the A/C control
head located on the instrument panel. The control
head includes the blower speed switch, rear wiper
and washer operation, front & rear window defogger,
recirculation door operation, and A/C compressor
operation if equipped. Refer to Group 8E, Instrument
Panel and Systems for service procedures.
NOTE: The RECIRC. function on the HVAC control
module automatically defaults to the OFF position
after a ignition key cycle. To reactivate the RECIRC.
function, the RECIRC. button must be repressedThe rear blower speed switch is serviced separately
from the control head.
SIDE DOOR HEATER A/C OUTLETS
The driver's and passenger side doors have supple-
mental air outlets and duct work. The air is chan-
neled from the instrument panel to the door duct and
either to the lower floor or upper door outlets (Fig.
4). The air can be adjusted to blow on the first rear
passenger seat(s).
SIDE WINDOW DEMISTER
The side window demisters direct air from the
heater assembly. The outlets are located on the top
forward corners of the front door panels (Fig. 5). The
demisters operate when the control mode selector is
on FLOOR, MIX or DEFROST setting.
SYSTEM AIRFLOW
The system pulls outside (ambient) air through the
cowl opening at the base of the windshield. Then it
goes into the plenum chamber above the heaterÐA/C
Fig. 3 HVAC Control Module
Fig. 4 Door Outlets
24 - 4 HEATING AND AIR CONDITIONINGNS
DESCRIPTION AND OPERATION (Continued)
Page 1821 of 1938

unit housing. On air conditioned vehicles, the air
passes through the evaporator. At this point the air
flow can be directed either through or around the
heater core. This is done by adjusting the blend- air
door with the TEMP control on the control head. An
optional zone control HVAC control module is avail-
able. This unit has dual blend-air doors that can be
regulated independently of each other. The tempera-
ture setting can be different from driver's side to pas-
senger side. After the air passes the blend-air door(s),
the air flow can then be directed from the Panel,
Floor, and Defrost outlets. Air flow velocity can be
adjusted with the blower speed selector switch on the
control head.
Ambient air intake can be shut off by closing the
recirculating air door. This will recirculate the air
that is already inside the vehicle. This is done by
depressing the Recirc. button on the control head. On
air conditioned vehicles, moving the control to Mix or
Defrost depresses the A/C button and will engage the
compressor. This will send refrigerant through the
evaporator, and remove heat and humidity from the
air before it goes through the heater core.
CAUTION: In cold weather, use of the Recirculation
mode may lead to excessive window fogging. The
Recirculation mode is automatically deactivated in
Mix and Defrost modes to improve window clearing
operation.
SYSTEM OIL LEVEL
It is important to have the correct amount of oil in
the A/C system to ensure proper lubrication of the
compressor. Too little oil will result in damage to the
compressor. Too much oil will reduce the cooling
capacity of the system and consequently result in
higher discharge air temperatures.NOTE: The oil used in the compressor is ND8 PAG
R134a refrigerant oil. Only refrigerant oil of the
same type should be used to service the system.
Do not use any other oil. The oil container should
be kept tightly capped until it is ready for use.
Tightly cap afterwards to prevent contamination
from dirt and moisture. Refrigerant oil will quickly
absorb any moisture it comes in contact with. Spe-
cial effort must be used to keep all R-134a system
components moisture-free. Moisture in the oil is
very difficult to remove and will cause a reliability
problem with the compressor.
It will not be necessary to check oil level in the
compressor or to add oil unless there has been an oil
loss. Oil loss at a leak point will be evident by the
presence of a wet, shiny surface around the leak.
REFRIGERANT OIL LEVEL CHECK
When an air conditioning system is first assem-
bled, all components (except the compressor) are
refrigerant oil free. After the system has been
charged with R134a refrigerant and operated, the oil
in the compressor is dispersed through the lines and
components. The evaporator, condenser, and filter-
drier will retain a significant amount of oil, refer to
the Refrigerant Oil Capacities chart. When a compo-
nent is replaced, the specified amount of refrigerant
oil must be added. When the compressor is replaced,
the amount of oil that is retained in the rest of the
system must be drained from the replacement com-
pressor. When a line or component has ruptured and
oil has escaped, the compressor should be removed
and drained. The filter-drier must be replaced along
with the ruptured part. The oil capacity of the sys-
tem, minus the amount of oil still in the remaining
components, can be measured and poured into the
suction port of the compressor.
Example: On a dual system the evaporator retains
60 ml (2 oz). The condenser retains 30 ml (1 oz) of
oil, and system capacity may be 220 ml (7.40 oz) of
oil.
220 ml minus 90 ml = 130 ml (4.40 oz).
Fig. 5 Demister Inlet
NSHEATING AND AIR CONDITIONING 24 - 5
DESCRIPTION AND OPERATION (Continued)
Page 1822 of 1938

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)
Page 1823 of 1938

DIAGNOSTICS
During the Actuator calibration, diagnostics are
performed on the actuators and evaporator tempera-
ture Fin Sensor. Once diagnostics are completed the
REAR WIPER and INTERMITTENT LED's will flash
to indicate either a successful calibration or the
appropriate fail code(s). At this time manual testing
of the Blend, Mode and Driver (if equipped) potenti-
ometers can be performed. If a failure is detected
during Diagnostics a fault will be set in the control.
When Ignition is cycled OFF and then ON or Diag-
nostics is aborted, the REAR WIPER and INTER-
MITTENT LED's will flash simultaneously showing
that a failure has occurred. The control will not indi-
cate the fail code, but only that a failure had
occurred during the last diagnostics test. The only
way to clear the failure codes is repeat the Calibra-
tion Diagnostic and Cooldown test, after all repairs
are completed.
COOLDOWN TEST
This test has been designed for performance test-
ing of the A/C system at the manufacturing facility. If
the HVAC control module is replaced, the Cooldown
test will occur during Calibration test. Cooldown will
not occur on Heater Only units. During the Cooldown
test the control will monitor the temperature of the
Fin Sensor. The A/C system must be able to bring the
evaporator temperature down a predetermined mini-
mum amount in less than 2 minutes.
CALIBRATION/COOLDOWN LED DISPLAY
CODES
See table for definition of flashing LED's. If no
problems are found, the control functions normally.
CALIBRATION/DIAGNOSTICS TEST ENTRY
TO INITIATE TESTS:
²Set Blower motor ON HIGH
²Set Mode position to Panel
²Open all A/C outlets
²Set Temperature to Cold (Both slide pots if
equipped)
²Depress WASH and REAR WIPER button simul-
taneously for 5 Seconds (Until all LED's light)
RESULTS:
²All LED's will turn on for 5 Seconds
²Calibration Test is running when REAR WIPER
and INTERMITTENT are alternately flashing.
Cooldown test is running if A/C and RECIRC are
alternately flashing.
²Acceptable results is REAR WIPER LED is the
only LED flashing. Push Rear Wiper to exit.
²After all tests have passed, Calibration Diagnos-
tics and Cooldown can be run separately.
Fig. 7 Radio Bezel and HVAC Control, Rear Blower
Motor Switch and Zone Control
CALIBRATION/COOLDOWN LED DISPLAY
CODES
LED'S PASS/FAILCORREC-
TIVE
ACTION
NO LED'S
FLASHING-
NORMAL
OPERATIONPASSED
CALIBRATION,
DIAGNOSTICS
AND
COOLDOWNNONE
REAR WIPER AND
INTERMITTENT
LED'S FLASH
SIMULTANEOUSLYFAILED
CALIBRATION
DIAGNOSTICSRUN
CALIBRATION
TEST
A/C AND RECIRC
LED'S FLASH
SIMULTANEOUSLYFAILED
COOLDOWNRUN
COOLDOWN
TEST
REAR WIPER AND
INTERMITTENT
LED'S ARE
FLASHING
SIMULTANEOUSLY
A/C AND RECIRC
LED'S ARE
FLASHING
SIMULTANEOUSLYFAILED
CALIBRATION,
DIAGNOSTICS
AND FAILED
COOLDOWN
TESTRUN
CALIBRATION
TEST
NSHEATING AND AIR CONDITIONING 24 - 7
DIAGNOSIS AND TESTING (Continued)
Page 1824 of 1938

COOLDOWN TEST ENTRY
TO INITIATE TESTS:
²Set Blower motor ON HIGH
²Set Mode position to Panel
²Open all A/C outlets
²Set Temperature to Cold (Both slide pots if
equipped)
²Depress WASH and A/C simultaneously for 5
Seconds
NOTE: Prior to start of test, If the evaporator is
already cold, the system will fail test. To correct,
operate system with A/C OFF and the blower motor
ON high for three minutes prior to starting test.
RESULTS:
²All LED's will turn on for 5 Seconds
²Cooldown Test is running when A/C and
RECIRC. are alternately flashing. If A/C and
RECIRC. are flashing simultaneously, Cooldown has
failed.
CALIBRATION DIAGNOSTICS AND
COOLDOWN ABORT
Test can be aborted by doing one of the following:
²Depressing Rear Window Defogger, RECIRC and
Rear Wiper buttons.
²Cycling Ignition OFF and then ON.
²Control will automatically abort after 15 min-
utes from the time Calibration Diagnostics and
Cooldown was entered.
The HVAC control module will return to normal
operation or may indicate unsuccessful Calibration
Diagnostics or Cooldown test by LED's flashing
simultaneously.
EEPROM DATA
Calibration Diagnostics, Cooldown Status and
evaporator temperature Fin Sensor values are stored
in an EEPROM memory internal to the control. The
microcomputer within the HVAC control module uses
this information:
²To determine if Cooldown needs to run
²For proper position of the Heater-A/C unit
assembly doors
ACTUATOR CALIBRATION AND
DIAGNOSTICS.
NOTE: Do not run actuators unless they are prop-
erly mounted on the HVAC control module.
Actuator end point calibration takes approximately
60 seconds. The REAR WIPER and INTERMITTENT
LED's will flash alternately during the test. The con-
trol will cycle the Blend actuator(s) to the Heat stopfirst then back to Cold. After the Blend actuator(s)
have been calibrated the Mode actuator will be cycled
to Defrost and then to Panel. Successful calibration
is defined as actuator travel falling within their min-
imum and maximum limits.
BLEND/PASSENGER ACTUATOR BACKGROUND
The Blend/Passenger Actuator can move the tem-
perature door in two directions. When the voltage at
Pin 12 of the control module is high, about 11.5 volts,
and the voltage at Pin 17 is low, about 1.5 volts, the
door will move towards the Heat position. When Pin
17 is High and Pin 12 is Low the door will move
towards the Cold position. When both Pins are high
or both Pins are low, the actuator will not move. The
Blend/Passenger feedback signal is a voltage signal
that is supplied by the actuator to the control. The
signal will be about 4.0 volts in the Heat position
and 1.0 volt in the Cold position. As the position of
the Blend/Passenger actuator changes, so will the
feedback signal. The feedback signal is necessary for
the correct positioning of the temperature door.
DRIVER ACTUATOR BACKGROUND
The Driver Actuator can move the temperature
door in two directions. When the voltage at Pin 15 of
the control module is high, about 11.5 volts, and the
voltage at Pin 13 is low, about 1.5 volts the door will
move towards the Cold position. When Pin 13 is High
and Pin 15 is Low the door will move towards the
Heat position. When both Pins are high or when both
Pins are low, the actuator will not move. The Driver
feedback signal is a voltage signal that is supplied by
the actuator to the control. The signal will be about
4.0 volts in the Heat position and 1.0 volt in the Cold
position. As the position of the Driver Actuator
changes, so will the feedback signal. The feedback
signal is necessary for the correct positioning of the
temperature door.
MODE ACTUATOR BACKGROUND
The Mode actuator can move the mode door in two
directions. When the voltage at Pin 18 of the control
module is high, about 11.5 volts, and the voltage at
Pin 12 is low, about 1.5 volts the door will move
towards the Panel position. When Pin 12 is High and
Pin 18 is Low the door will move towards the Defrost
position. When both Pin are high or when both Pins
are low, the actuator will not move. The Mode door
feedback signal is a voltage signal that is supplied by
the actuator to the control. The signal will be about
4.5 volts in the Panel position and 0.5 volts in the
Defrost position. As the position of the Mode actuator
changes, so will the feedback signal. The feedback
signal is necessary for the correct positioning of the
mode door.
24 - 8 HEATING AND AIR CONDITIONINGNS
DIAGNOSIS AND TESTING (Continued)