FAIL CODES/LEVEL DISPLAY
Fail Codes/Level are displayed using the REAR
WIPER and INTERMITTENT LED's flashing in the
sequence indicated below. The REAR WIPER LED
represents the Level and the INTERMITTENT LED
represents the Value. After Calibration/Diagnostics is
completed, the control will begin flashing Level 1
codes. Depressing the WASH button will cycle to
Level 2, depressing WASH again will cycle to Level 3.
Each time the WASH button is depressed will cycle
to the next level. After Level 5 is reached, you will
cycle back to Level 1. If the Control is a Heater Only
you will only cycle from Levels 1 to 3.
TEMPERATURE AND MODE POTENTIOMETER
DIAGNOSTICS
The Temperature and Mode Potentiometer can be
tested after calibration is complete by pressing the
WASH button and cycling to Levels 2, 3 or 5 as dis-
played by the REAR WIPER LED. On Heater Only
units you can only cycle to Levels 2 and 3. In eachindividual test the INTERMITTENT LED flash rate
will change as the Temperature or Mode potentiome-
ter is moved from one end to the other, see Potenti-
ometer vs. Position and Flash Rate table.
EVAPORATOR PROBE TEMPERATURE
DIAGNOSTICS
The evaporator probe can be tested by using the
INTERMITTENT LED to display the actual temper-
ature the sensor is reading. The HVAC control mod-
ule can only display temperatures from 1 to 99
degrees. To read the temperature, perform the follow-
ing:
²Set Blower motor to any speed other than OFF
²Set A/C to ON, if A/C Clutch does not engage
make sure Fail Codes 5 and 6 are cleared.To clear
the error code 5 and 6 the evaporator probe and/or
the wiring repair needs to be completed. Then, press
and hold the intermittent wipe button for 5 seconds.
²Run Diagnostics (Depress REAR WIPER and
REAR WASH)
²When Diagnostics is complete, Cycle to Level 4.
Display Sequence is as follows:
²REAR WIPER LED will display the Level
²INTERMITTENT LED will display ten's digit
²Short Pause
²INTERMITTENT LED will display the one's
digit.
The HVAC control module will continue to cycle
the Level and then Temperature until the level is
changed or Calibration Diagnostics and Cooldown
test is exited.
HVAC CONTROL DIAGNOSTIC CONDITIONS
For wiring circuits, wiring connectors, and Pin
numbers, refer to Group 8W, Wiring Diagrams.
After calibration, Rear Wiper LED flashing
once, Intermittent LED not flashing.
The system has passed calibration. Press the Rear
Wiper button to exit calibration.
WIPE BUTTON LED
LEVEL DISPLAY
1 FAIL CODES
2 MODE POTENTIOMETER TEST
3 BLEND/PASS. POTENTIOMETER TEST
4 EVAPORATOR PROBE (A/C AND ZONE
UNITS ONLY)
5 DRIVER POTENTIOMETER (ZONE UNITS
ONLY)
LEVEL 1±FAILURE CODE VALUES
(INTERMITTENT WIPE BUTTON LED)
CODE DEFINITION
0 PASSED ALL TESTS
1 MODE ACTUATOR DID NOT REACH
DEFROST POSITION
2 MODE ACTUATOR DID NOT REACH
PANEL POSITION
3 BLEND/PASS. ACTUATOR DID NOT
REACH COLD STOP
4 BLEND PASS. ACTUATOR DID NOT
REACH HEAT STOP
5 EVAPORATOR PROBE OPEN
6 EVAPORATOR PROBE SHORTED
7 DRIVER ACTUATOR DID NOT REACH
COLD STOP
8 ZONE/DRIVER ACTUATOR DID NOT
REACH HEAT STOP
9 CONTROL HEAD INTERNAL FAILURE
POTENTIOMETER VS. POSITION AND FLASH
RATE
POTENTIOM-
ETERINTERMIT-
TENT LED
FASTER
FLASH RATEINTERMITTENT
LED SLOWER
FLASH RATE
MODE PANEL DEFROST
BLEND/PASS. HOT COLD
DRIVER HOT COLD
NSHEATING AND AIR CONDITIONING 24 - 9
DIAGNOSIS AND TESTING (Continued)
BLOWER MOTOR AND WHEEL ASSEMBLY
VIBRATION AND/OR NOISE DIAGNOSIS
The blower speed switch, in conjunction with the
resistor block, supplies the blower motor with varied
voltage.
CAUTION: Stay clear of the blower motor and resis-
tor block (Hot). Do not operate the blower motor
with the resistor block removed from the heater A/C
housing.
Refer to the Blower Motor Vibration/Noise chart in
this section for diagnosis.
COMPRESSOR NOISE DIAGNOSIS
Excessive noise while the A/C is being used, can be
caused by loose mounts, loose clutch, or high operat-
ing pressure. Verify compressor drive belt condition,
proper refrigerant charge and head pressure before
compressor repair is performed.
If the A/C drive belt slips at initial start-up, it does
not necessarily mean the compressor has failed.
With the close tolerances of a compressor it is pos-
sible to experience a temporary lockup. The longer
the A/C system is inactive, the more likely the condi-
tion to occur.
This condition is the result of normal refrigerant
movement within the A/C system caused by temper-
ature changes. The refrigerant movement may wash
the oil out of the compressor.
COMPRESSOR CLUTCH/COIL
The air conditioning compressor clutch electrical
circuit is controlled by the Powertrain Control Mod-
ule. It is located in the engine compartment outboard
of the battery.If the compressor clutch does not engage verify
refrigerant charge.
If the compressor clutch still does not engage check
for battery voltage at the pressure transducer located
on the liquid line. If voltage is not detected, refer to:
²Group 8W, Wiring diagrams.
²Powertrain Diagnostic Procedures manual for
diagnostic information.
If voltage is detected at the pressure transducer,
connect pressure transducer and check for battery
voltage between the compressor clutch connector ter-
minals.
If voltage is detected, perform A/C Clutch Coil
Tests.
TESTS
(1) Verify battery state of charge. (Test indicator in
battery should be green).
(2) Connect an ampmeter (0-10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0-20 volt scale) with clip leads measuring voltage
across the battery and A/C clutch.
(3) With A/C control in A/C mode and blower at
low speed, start the engine and run at normal idle.
(4) The A/C clutch should engage immediately and
the clutch voltage should be within two volts of the
battery voltage. If the A/C clutch does not engage,
test the fuse.
(5) The A/C clutch coil is acceptable if the current
draw is 2.0 to 3.7 amperes at 11.5-12.5 volts at clutch
coil. This is with the work area temperature at 21ÉC
(70ÉF). If voltage is more than 12.5 volts, add electri-
cal loads by turning on electrical accessories until
voltage reads below 12.5 volts.
(6) If coil current reads zero, the coil is open and
should be replaced. If the ammeter reading is 4
amperes or more, the coil is shorted and should be
replaced. If the coil voltage is not within two volts of
the battery voltage, test clutch coil feed circuit for
excessive voltage drop.
EXPANSION VALVE
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.
TESTS
NOTE: Expansion valve tests should be performed
after compressor tests.
Review Safety Precautions and Warnings in this
group. The work area and vehicle temperature must
A/C PRESSURE TRANSDUCER VOLTAGE
VOLTAGE CONDITION
0 TRANSDUCER FAULTY
OR NO VOLTAGE FROM
PCM
.150 TO .450 TRANSDUCER
GOOD/LOW PRESSURE
CUTOUT CONDITION
.451 TO 4.519 NORMAL OPERATING
CONDITION
4.520 TO 4.850 TRANSDUCER
GOOD/HIGH
PRESSURE CUTOUT
CONDITION
5 TRANSDUCER FAULTY
NSHEATING AND AIR CONDITIONING 24 - 13
DIAGNOSIS AND TESTING (Continued)
DIAGNOSIS AND TESTING
DIAGNOSTIC PROCEDURES
When diagnosing electrical problems in the auxil-
iary rear heater or rear A/C system, refer to Group
8W, Wiring Diagrams.
When diagnosing problems in the auxiliary sys-
tems, refer to diagnostic sections for front heater A/C.
REMOVAL AND INSTALLATION
AIR DISTRIBUTION DUCT-A/C
REMOVAL
(1) Remove quarter trim panel, D-pillar, and head-
liner (Fig. 8). Refer to Group 23, Body.
(2) Remove screws securing D-pillar duct to quar-
ter panel. Pull duct up and away from unit.
(3) Remove screws securing duct to rear header
(Fig. 9).
(4) Remove screws securing duct to right and left
rails (Fig. 10).
INSTALLATION
For installation, reverse the above procedures.
AIR DISTRIBUTION DUCT-HEATER
REMOVAL
(1) Remove quarter trim panel and D-pillar (Fig.
8) and (Fig. 11). Refer to Group 23, Body.
(2) Remove screws securing lower heat duct to
housing.
INSTALLATION
For installation, reverse the above procedures.
Fig. 7 Rear Blower Switch
Fig. 8 Quarter Trim Panel
Fig. 9 Rear Crossover Duct
Fig. 10 Upper A/C Duct
NSHEATING AND AIR CONDITIONING 24 - 43
DESCRIPTION AND OPERATION (Continued)
capacity of the system and consequently result in
higher discharge air temperatures.
NOTE: The oil used in the Denso 2.5L Turbo Diesel
and the Denso 2.0L gasoline engine compressors is
ND-8 PAG R134a refrigerant oil. Only refrigerant oil
of the same type should be used to service the sys-
tem. 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 contamina-
tion from dirt and moisture. Refrigerant oil will
quickly absorb any moisture it comes in contact
with. 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 reli-
ability 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 compressor is drained through the
suction port or by removing the sump bolt on top of
the compressor, refer to Compressor Removal and
Installation procedures. The filter-drier must be
replaced along with the ruptured part. The oil capac-
ity of the system, minus the amount of oil still in the
remaining components, can be measured and poured
into the suction port of the compressor.
Example: The evaporator retains 50 ml (1.7 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.).
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 the Denso 2.5L Turbo Diesel and Denso 2.0L gas-
oline engine compressors is ND-8 PAG compressor
oil. For gasoline vehicles still using R-12 refrigerant,
use ND8 PAG compressor oil.
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 calibration.
ACTUATOR CALIBRATION
Mode, Blend and Zone (if equipped) door calibra-
tion compensates for mechanical variations in the
REFRIGERANT OIL CAPACITIES
REFRIGERANT OIL CAPACITIES
COMPONENT ML OZ
Compressor 135 ml 4.5 oz
Filter-Drier 30 ml 1.0 oz
Condenser 30 ml 1.0 oz
Evaporator 50 ml 1.7 oz
NS/GSHEATING AND AIR CONDITIONING 24 - 5
DESCRIPTION AND OPERATION (Continued)
²Set A/C to ON, if A/C Clutch does not engage
make sure Fail Codes 5 and 6 are cleared.To clear
the error code 5 and 6 the evaporator probe and/or
the wiring repair needs to be completed. Then, press
and hold the intermittent wipe button for 5 seconds.
²Run Diagnostics (Depress REAR WIPER and
REAR WASH)
²When Diagnostics is complete, Cycle to Level 4.
Display Sequence is as follows:
²REAR WIPER LED will display the Level
²INTERMITTENT LED will display ten's digit
²Short Pause
²INTERMITTENT LED will display the one's
digit.
The HVAC control module will continue to cycle
the Level and then Temperature until the level is
changed or Calibration Diagnostics and Cooldown
test is exited.
HVAC CONTROL DIAGNOSTIC CONDITIONS
For wiring circuits, wiring connectors, and Pin
numbers, refer to Group 8W, Wiring Diagrams.
After calibration, Rear Wiper LED flashing
once, Intermittent LED not flashing.
The system has passed calibration. Press the Rear
Wiper button to exit calibration.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing once. The
mode actuator did not reach defrost position.
(1) Using a voltmeter, check the mode door actua-
tor wiring connector. Check Pin 1 for battery voltage.
Move the HVAC control from the defrost to panel
position, and check Pin 6 voltage it should change
from 0.5 - 1 volts to 3.5 - 4.5 volts. If voltage is OK,
go to Step 2. If not OK, check for loose or corroded
connector, open or shorted circuit and repair as nec-
essary.
(2) Remove actuator, and check if the gear pins are
in the correct track on cam or if they are binding. If
OK, go to Step 3. If not OK, repair as necessary.
(3) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(4) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing twice. The
mode actuator did not reach panel position.
(1) Using a voltmeter, check the mode door actua-
tor wiring connector. Check Pin 1 for battery voltage.
Move the HVAC control from panel to defrost posi-
tion, and check Pin 6 voltage it should change from
3.5 - 4.5 volts to 0.5 - 1 volts. If voltage is OK, go toStep 2. If not OK, check for loose or corroded connec-
tor, open or shorted circuit and repair as necessary.
(2) Remove actuator, and check if the gear pins are
in the correct cam track or binding. If OK, go to Step
3. If not OK, repair as necessary.
(3) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(4) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing three times.
The main temperature actuator/passenger
temperature actuator on a zone system did
not reach cold stop.
(1) Check if the correct HVAC control module was
used.
(2) Using a voltmeter, check the temperature door
actuator wiring connector. Check Pin 1 for battery
voltage. Move the HVAC control from the cold to hot
position, and check Pin 5 voltage it should change
from 0.5 - 4 volts to 3.5 - 4.5 volts. If voltage is OK,
go to Step 3. If not OK, check for loose or corroded
connector, open or shorted circuit and repair as nec-
essary.
(3) Remove actuator, and check if gear pins are in
the correct cam track or binding. If OK, go to Step 4.
If not OK, repair as necessary.
(4) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(5) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing four times.
The main temperature actuator/passenger
temperature actuator on a zone system did
not reach hot stop.
(1) Check if the correct HVAC control module was
used.
(2) Using a voltmeter, check the temperature door
actuator wiring connector. Check Pin 1 for battery
voltage. Move the HVAC control from hot to cold
position and check Pin 5 voltage it should change
from 3.5 -4.5 volts 0.5 - 1.5 volts. If voltage is OK, go
to Step 3. If not OK, check for loose or corroded con-
nector, open or shorted circuit and repair as neces-
sary.
(3) Remove actuator, and check if the gear pins are
in the correct track on cam or if they are binding. If
OK, go to Step 4. If not OK, repair as necessary.
NS/GSHEATING AND AIR CONDITIONING 24 - 9
DIAGNOSIS AND TESTING (Continued)
BLOWER MOTOR AND WHEEL ASSEMBLY
VIBRATION AND/OR NOISE DIAGNOSIS
The blower speed switch, in conjunction with the
resistor block, supplies the blower motor with varied
voltage.
CAUTION: Stay clear of the blower motor and resis-
tor block (Hot). Do not operate the blower motor
with the resistor block removed from the heater A/C
housing.
Refer to the Blower Motor Vibration/Noise chart in
this section for diagnosis.
COMPRESSOR NOISE DIAGNOSIS
Excessive noise while the A/C is being used, can be
caused by loose mounts, clutch, or high operating
pressure. Verify compressor drive belt condition,
proper refrigerant charge and head pressure before
compressor repair is performed.
COMPRESSOR CLUTCH/COIL
The air conditioning compressor clutch electrical
circuit is controlled by the Powertrain Control Mod-ule. It is located in the engine compartment outboard
of the battery.
If the compressor clutch does not engage verify
refrigerant charge.
If the compressor clutch still does not engage check
for battery voltage at the pressure transducer located
on the liquid line. If voltage is not detected, refer to:
²Group 8W, Wiring diagrams.
²Powertrain Diagnostic Procedures manual for
diagnostic information.
If voltage is detected at the pressure transducer,
connect pressure transducer and check for battery
voltage between the compressor clutch connector ter-
minals.
If voltage is detected, perform A/C Clutch Coil
Tests.
TESTS
(1) Verify battery state of charge. (Test indicator in
battery should be green).
(2) Connect an ampmeter (0-10 ampere scale) in
series with the clutch coil terminal. Use a voltmeter
(0-20 volt scale) with clip leads measuring voltage
across the battery and A/C clutch.
(3) With A/C control in A/C mode and blower at
low speed, start the engine and run at normal idle.
(4) The A/C clutch should engage immediately and
the clutch voltage should be within two volts of the
battery voltage. If the A/C clutch does not engage,
test the fuse.
(5) The A/C clutch coil is acceptable if the current
draw is 2.0 to 3.7 amperes at 11.5-12.5 volts at clutch
coil. This is with the work area temperature at 21ÉC
(70ÉF). If voltage is more than 12.5 volts, add electri-
cal loads by turning on electrical accessories until
voltage reads below 12.5 volts.
Fig. 7 A/C PERFORMANCE TEMPERATURES
VOLTAGE CONDITION
0 Transducer faulty or no voltage
from PCM
.150 to .450 Transducer good/Low Pressure
Cutout condition
.451 to 4.519 Normal operating condition
4.520 to 4.850 Transducer good/High
Pressure Cutout condition
5 Transducer faulty
24 - 12 HEATING AND AIR CONDITIONINGNS/GS
DIAGNOSIS AND TESTING (Continued)