HVAC System - Automatic Chevrolet Malibu VI рестайлинг

Fastener Tightening Specifications

Fastener Tightening Specifications

Sensor Resistance Table (Ambient Air Temp Sensor)

The Tech 2 will display sensor value as a voltage. This gives the approximate voltage expected at different ambient temperatures as well as what should be read with an ohmmeter connected to the sensor. Since this is raw data any heat from underhood that changes ambient temp around the sensor might skew the reading, so let the engine compartment cool.

Sensor Resistance Table (Ambient Air Temp Sensor)

Sensor Resistance Table (Duct Temp conversion temp to counts)

Sensor Resistance Table (Duct Temp conversion temp to counts)

Sensor Resistance Table (Inside Air Temperature Sensor)

Sensor Resistance Table (Inside Air Temperature Sensor)

Sensor Resistance Table (Upper and Lower Duct Temp Sensors)

Sensor Resistance Table (Upper and Lower Duct Temp Sensors)

Scheme 38

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Scheme 51

A/C Compressor Clutch Connector Part Information

A/C Compressor Clutch Connector Terminal Identification

Scheme 52

A/C Refrigerant Pressure Sensor Connector Part Information

A/C Refrigerant Pressure Sensor Connector Terminal Identification

Scheme 53

Air Temperature Actuator Connector Part Information

Air Temperature Actuator Connector Terminal Identification

Scheme 54

Air Temperature Sensor Connector Part Information (Lower)

Air Temperature Sensor Connector Terminal Identification (Lower)

Air Temperature Sensor - Upper

Air Temperature Sensor Connector Part Information (Upper)

Air Temperature Sensor Connector Terminal Identification (Upper)

Scheme 55

Ambient Air Temperature Sensor Connector Part Information

Ambient Air Temperature Sensor Connector Terminal Identification

Scheme 56

Blower Motor Connector Part Information

Blower Motor Connector Terminal Identification

Scheme 57

Blower Motor Control Module Connector Part Information

Blower Motor Control Module Connector Terminal Identification

Scheme 58

HVAC Control Module Connector Part Information

HVAC Control Module Connector Terminal Identification

Scheme 59

Mode Actuator Connector Part Information

Mode Actuator Connector Terminal Identification

Recirculation Actuator

Recirculation Actuator Connector Part Information

Recirculation Actuator Connector Terminal Identification

Scheme 60

Sunload Sensor Connector Part Information

Sunload Sensor Connector Terminal Identification

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Scan Tool Output Controls

BCM Scan Tool Output Controls

HVAC Scan Tool Output Controls

PCM/ECM Scan Tool Output Controls

Scan Tool Data List

Use the Scan Tool Data Display Values and Definitions in order to assist in diagnosing the HVAC control module concerns. Compare the vehicles actual scan tool data with the typical data display value table information. Use the data information in order to aid in understanding the nature of the concern when the vehicle does not match with the typical data display values.

The scan tool data values were taken from a known good vehicle under the following conditions

1. The ignition switch is in the ON position.
2. The engine is running at idle.
3. The vehicle is in PARK.
4. The doors are closed.
5. The windows are closed.
6. The A/C is ON.
7. The ambient air temperatures are at 22-27°C (70-80°F).

Heating and Air Conditioning

PCM 2.2L L61/PCM 3.5L LX9/ECM 3.9L LZ9

BCM

Circuit Description

The HVAC control module monitors air temperature through air temperature sensors. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low. The HVAC control module requests A/C compressor clutch engagement and controls the appropriate mode and air temperature actuator door positions in order to maintain the selected air temperature on the HVAC control module.

The inside air temperature sensor is contained within the HVAC control module. The replacement of the inside air temperature sensor involves the replacement of the HVAC control module. The inside air temperature sensor provides the HVAC control module with the temperature of the air drawn through an aspirator from the passenger compartment across a sensor. A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device which is proportional to temperature. As the air temperature increases, the resistance decreases and the voltage signal decreases. As the air temperature decreases, the resistance increases and the voltage signal increases.

Output air temperature sensor 1 circuit refers to the a/c upper duct air temperature sensor.

Output air temperature sensor 2 circuit refers to the heater lower duct air temperature sensor.

Passenger compartment temperature sensor 1 circuit refers to the inside air temperature sensor.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC B0164 Passenger Compartment Temperature Sensor Circuit Range/Performance
2. DTC B0174 Output Air Temperature Sensor 1 Circuit
3. DTC B0179 Output Air Temperature Sensor 2 Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

The HVAC control module monitors the signal circuit of the appropriate duct or inside air temperature sensor for the following conditions

DTC B0164, B0174, or B0179

Conditions for Running the DTC

The ignition is turned ON.

B0164 05 and 06

The HVAC control module detects the inside air temperature sensor signal circuit is less than 2 counts or greater than 253 counts for 30 seconds.

B0174 or B0179 05 and 06

The HVAC control module detects the signal circuit is less than 5 counts (0.09 V) or greater than 250 counts (4.90 V).

If the DTC sets due to the low condition, the HVAC control module will default to maximum cooling, except when the maximum heating setting is selected. If the DTC sets due to the high condition, the HVAC control module will default to maximum heating, except when the maximum cooling setting is selected.

B0174 05 and 06

A default value will be used for the sensor data by the HVAC control module.

Conditions for Clearing the DTC

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 40 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

Diagnostic Aids

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 4: Tests for the proper operation of the circuit in the high voltage range.
2. 5: Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

DTC B0164, B0174, or B0179

The sunload sensor is a 2-wire photo diode. This vehicle uses a single sunload sensor. The sensor is integrated into the ambient light sensor assembly. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts. The sunload sensor provides the HVAC control module with a measurement of the amount of light shining on the vehicle. Bright or high intensity light cause the vehicle's inside temperature to increase. The HVAC System compensates for the increased temperature by diverting additional cool air into the vehicle.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B0183 Solar Load Sensor 1 Circuit.

This vehicle has DTCs which include DTC Symptoms, refer to DTC Symptom Description .

DTC B0183

The ignition is turned ON.

B0183 02 and 05

The HVAC control module detects the signal circuit is less than 5 counts (0.09 volt) or more than 250 counts (4.90 volts).

If the DTC sets due to a low voltage condition, the HVAC control module will operate the system as if a maximum sunload condition exists. If the DTC sets due to a high voltage condition, the HVAC control module will operate the system as if a minimum sunload condition exists.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 40 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

1. 3: Tests for the proper operation of the circuit in the high count (high voltage) range.
2. 4: Tests for the proper operation of the circuit in the low count (low voltage) range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

DTC B0183

The actuators are a 2-wire bi-directional electric motor. Two control circuits enable the actuators to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuators in the opposite direction. The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. The HVAC control module commands the actuator to each extreme position and counts the total number of pulses. The HVAC control module compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful.

1. Temperature control 1 circuit refers to the air temperature actuator.
2. Air flow control 3 circuit refers to the mode actuator.
3. Air flow control 7 circuit refers to the recirculation actuator.

This diagnostic procedure supports the following DTCs

1. DTC B0248 Air Flow Control 3 Circuit
2. DTC B0268 Air Flow Control 7 Circuit
3. DTC B0408 Temperature Control 1 Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC B0248, B0268, or B0408

1. The ignition is turned ON.
2. The ignition voltage is between 9-16 volts.

2A and 61

Sets after 2 occurrences of the test fail code setting conditions listed below in the same ignition cycle.

51 and 04

Sets after one occurrence of the test fail code setting conditions listed below in the same ignition cycle.

2A, 04, 51 and 61

The following failures occur and set the DTC

1. The HVAC control module does not detect any movement of the actuator.
2. The HVAC control module detects a measured actuator range that exceeds the calibratible value.
3. The HVAC control module detects a measured actuator range that is less than the calibratible value.
4. The HVAC control module detects a calibratible procedure time that exceeds the calibratible value.
5. The HVAC control module detects the actuator motor as stalled before the actuator motor reaches the expected stall at the end of the travel. When the drive voltage is reversed, the motor is unable to move more than a calibratible amount in the other direction.
6. The HVAC control module detects the actuator motor as stalled before the actuator motor reaches the expected stall at the end of the travel. But, when the drive voltage is reversed, the motor is able to move more than a calibratible amount in the other direction.

2A

The HVAC control module will use a default range to retry calibration procedure when the ignition is OFF.

61

The HVAC control module will stop trying to move the air temperature actuator motor during the current ignition cycle.

04

The HVAC control module will retry the command to move the actuator in a certain direction in 5-minute intervals.

51

The HVAC control module will retry calibration when the ignition is OFF.

Conditions for Clearing the MIL/DTC

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 40 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. Inspect the actuator door and actuator for the following conditions: A misaligned air temperature actuator. Refer to «Air Temperature Actuator Replacement»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic) . Broken or binding linkages or actuator door Obstruction that prevents the actuator door from operating within its full range of motion Missing seals to the actuator door Misaligned seals to the actuator door
2. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vi-2006-2008/remont/ignition-switchsteering-lock/#wiring-systems-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor) .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This step verifies that the HVAC control module is able to command the appropriate actuator through its full range of motion.
2. 3: This step verifies the position of the actuators.
3. 4: If the actuator does not move at all, the problem is likely to be the drive circuitry within the HVAC control module, the actuator, or the wiring harness. If the actuator does move, but not within its full range of motion, the problem is likely to be a mechanical binding of the actuator door or actuator door linkage.
4. 6: This step drives the actuator in one position. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
5. 7: This step drives the actuator in the opposite direction.

DTC B0248, B0268, or B0408

The powertrain control module (PCM) or engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The PCM/ECM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure sensor signal to the PCM/ECM to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. When pressure is high, the PCM/ECM commands the cooling fans ON. When pressure is too high or too low, the PCM/ECM will not allow the A/C compressor clutch to engage.

This diagnostic procedure supports the following DTCs

1. DTC P0532 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage.
2. DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage.

The ignition is ON.

Conditions for Setting the DTC

All of the following conditions exist for 15 seconds.

1. The PCM/ECM detects that the A/C pressure is 9 psi (0.2 volt) or less.
2. The PCM/ECM detects that the A/C pressure is more than 453 psi (4.92 volts).
3. The PCM/ECM detects a too low or too high signal on the A/C refrigerant pressure sensor signal circuit.

Action Taken When the DTC Sets

1. The PCM/ECM will not illuminate the malfunction indicator lamp (MIL).
2. The PCM/ECM stores the Failure Records.
3. The A/C compressor clutch is disabled.

1. The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction.
2. The DTC can be cleared by using the scan tool.
3. The DTC will become history if the PCM/ECM no longer detects a failure.

Test the following conditions

1. Visually inspect the sensor for contamination or damage.
2. Inspect for the following that may affect the sensor accuracy: A malfunction within the refrigerant system causing high pressure Visually inspect the A/C components and lines for damage.
3. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vi-2006-2008/remont/ignition-switchsteering-lock/#wiring-systems-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor) .

The numbers below refer to the step numbers on the diagnostic table.

1. 4: This step tests for the proper operation of the circuit in the low voltage range.
2. 5: This step tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
3. 6: This step tests for a short to voltage in the 5-volt reference circuit.
4. 7: This step tests for a high resistance or an open in the low reference circuit.

DTC P0532 or P0533

Ignition voltage is supplied directly to the A/C compressor clutch relay. The powertrain control module (PCM) or engine control module (ECM) controls the relay by grounding the A/C clutch relay control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. The driver has a fault line which is monitored by the PCM/ECM. When the PCM/ECM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the PCM/ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.

The PCM/ECM will monitor the control circuit for the following

1. A short to ground
2. A short to voltage
3. An open circuit
4. An open relay coil
5. An internally shorted or excessively low resistance relay coil

When the PCM/ECM detects any of the above malfunctions, this DTC is set and the affected driver is disabled.

This diagnostic procedure supports the following DTCs

DTC P0645 Air Conditioning A/C Clutch Relay Control Circuit

This vehicle has DTCs which include DTC Symptoms, refer to Symptoms - Vehicle .

1. The ignition voltage is between 9-18 volts.
2. The engine speed is more than 80 RPM.
3. The PCM/ECM driver transitions from ON to OFF or from OFF to ON.

The PCM/ECM detects an open on the control circuit of the A/C compressor clutch relay.

1. The PCM/ECM will not illuminate the malfunction indicator lamp (MIL).
2. The PCM/ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

1. A History DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.
2. The DTC can be cleared by using a scan tool.

If DTCs P0645 cannot be duplicated, reviewing the Failure Records vehicle millage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections .

The numbers below refer to the step numbers on the diagnostic table.

1. 2: Listen for an audible click when the A/C compressor clutch relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
2. 3: This step tests for voltage at the coil side of the A/C compressor clutch relay. The 10-amp fuse supplies power to the coil side of the A/C compressor clutch relay.
3. 4: This step verifies that the PCM/ECM is providing ground to the A/C compressor clutch relay. If the light is always ON, the circuit is shorted to ground.
4. 8: This step tests for a short to voltage or an open.
5. 10: If the A/C fuse is open, ensure to test the A/C compressor clutch supply voltage circuit for short to ground.

DTC P0645

Symptoms - HVAC Systems - Automatic

1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/malibu/vi-2006-2008/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) , before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to: «Air Delivery Description and Operation»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__air-delivery-description-and-operation) «Air Temperature Description and Operation»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__air-temperature-description-and-operation)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(/chevrolet/malibu/vi-2006-2008/remont/ignition-switchsteering-lock/#wiring-systems-power-management-service-troubleshooting-diagnosis__checking-aftermarket-accessories) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating steering wheel or passenger HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__air-temperature-description-and-operation) .
6. The following conditions may cause window fogging: Wet carpet or mats High humidity Interior water leak Blocked A/C evaporator drain tube Maximum passenger capacity Blocked body pressure relief valves
7. Inspect the air distribution system for causes of reduced air flow: Obstructed or dirty passenger compartment air filter, if equipped Blocked or damaged air inlet or outlet vents

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «HVAC Compressor Clutch Does Not Engage (L61)»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic) or «HVAC Compressor Clutch Does Not Engage (LX9/LZ9)»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic)
2. «HVAC Compressor Clutch Does Not Disengage»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__hvac-compressor-clutch-does-not-disengage)
3. «Blower Motor Always On»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__blower-motor-always-on)
4. «Blower Motor Inoperative»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__blower-motor-inoperative)
5. «Blower Motor Malfunction»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__blower-motor-malfunction)
6. «Too Hot in Vehicle»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic)
7. «Too Cold in Vehicle»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic)
8. «Air Delivery Improper»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic)
9. «Air Recirculation Malfunction»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic)
10. «Leak Testing»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__leak-testing)
11. «Defrosting Insufficient»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__defrosting-insufficient)
12. «Noise Diagnosis - Blower Motor»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-blower-motor)
13. «Noise Diagnosis - Air Conditioning (A/C) System»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-air-conditioning-ac)
14. «Odor Diagnosis»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__odor-diagnosis)
15. «Noise Diagnosis - HVAC Module»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-hvac-module)

The numbers below refer to the step numbers on the diagnostic table.

1. 2: The A/C compressor relay output is disabled if engine coolant temperature is above 128°C (262°F). The instrument panel engine coolant indicator will indicate overheating.

1. 3: Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level mode for consistent testing of the A/C system operation.
2. 6: The HVAC control module is inoperative if the module does not respond to any operator control requests.

HVAC Compressor Clutch Does Not Engage (L61)

The numbers below refer to the step numbers on the diagnostic table.

1. 2: The A/C compressor relay output is disabled if engine coolant temperature is above 128°C (262°F). The instrument panel engine coolant indicator will indicate overheating.

1. 3: Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level mode for consistent testing of the A/C system operation.
2. 6: The HVAC control module is inoperative if the module does not respond to any operator control requests.

HVAC Compressor Clutch Does Not Engage (LX9/LZ9)

HVAC Compressor Clutch Does Not Disengage

HVAC Compressor Clutch Does Not Disengage

Blower Motor Always On

Blower Motor Always On

Blower Motor Inoperative

Blower Motor Inoperative

Blower Motor Malfunction

Blower Motor Malfunction

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This test resets HVAC control module and checks for current air temperature actuator DTC.
2. 7: Ambient air temperature must be above 3°C (38°F) in order for this A/C Compressor test to be run.

Too Hot in Vehicle

The numbers below refer to the step numbers on the diagnostic table.

1. 2: This test resets HVAC control module and checks for current air temperature actuator DTC.
2. 8: This checks for proper operation of coolant system to ensure heater output.

Too Cold in Vehicle

1. The condition may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vi-2006-2008/remont/ignition-switchsteering-lock/#wiring-systems-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor) .
2. Ensure that the panel vents are in the OPEN position for proper diagnosis.
3. Inspect the air delivery system for the following conditions: An obstruction to the airflow Air leaks Misaligned air ducts Broken or binding linkages or doors
4. If the scan tool indicates that the Door Actual parameter is 5-10 counts from the Commanded Door parameter, then perform the recalibration procedure for the HVAC door actuators. Refer to «Re-Calibrating Actuators»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__re-calibrating-actuators) .

Air Delivery Improper

1. The condition may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/malibu/vi-2006-2008/remont/ignition-switchsteering-lock/#wiring-systems-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-and-poor) .
2. Inspect the air delivery system for the following conditions: An obstruction to the airflow Air leaks Misaligned air ducts Broken or binding linkages or doors
3. If the scan tool indicates that the Door Actual parameter is 5-10 counts from the Commanded Door parameter, then perform the recalibration procedure for the HVAC door actuators. Refer to «Re-Calibrating Actuators»(/chevrolet/malibu/vi-2006-2008/remont/automatic-hvac-system/#hvac-system-automatic__re-calibrating-actuators) .

Air Recirculation Malfunction

Afterblow Enabling

The afterblow mode can be enabled using the scan tool. The afterblow mode allows the blower motor to operate after the engine has been turned off. This operation of the blower motor dries the evaporator core, which reduces the amount of microbial growth which can create undesirable odors.

Use the following procedure in order to enable the afterblow mode

1. Connect the Scan Tool.
2. Turn ON the ignition, with the engine OFF.
3. Select HVAC Module.
4. Select HVAC Systems Automatic.
5. Select Special Functions.
6. Select HVAC.
7. Select Afterblow Option.
8. Select ENTER to enable the afterblow.
9. When done, use the soft key to save changes.

When afterblow has been enabled by the scan tool the blower motor will operate at high speed for 4 minutes after the engine has been turned off.

The following conditions must be met for the HVAC module to operate the afterblow

1. The outside air temperature must be at least 21°C (70°F).
2. The A/C compressor must operate for more than 2 minutes.
3. The engine must be turned off for at least 45 minutes.
4. The system voltage must be at least 12 volts.

Re-Calibrating Actuators

When replacing the HVAC control module it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC control module be sure to perform the following

1. Place the ignition switch to the OFF position.
2. Disconnect the scan tool.
3. Install the HVAC control module.
4. Connect all previously disconnected components.
5. Start the vehicle.
6. Wait 40 seconds for the HVAC control module to self-calibrate.
7. Verify that no DTCs have set as current DTCs.

When replacing the HVAC actuator it will be necessary to allow the HVAC control module to perform a calibration process. When installing the HVAC actuator be sure to perform the following

Calibration Procedure

1. Clear all DTCs.
2. Place the ignition switch to the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Remove the HVAC (BATT) fuse for a minimum of 10 seconds.
6. Install the HVAC (BATT) fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

Removal Procedure

1. Remove the instrument panel (I/P) center trim panel. Refer to «Instrument Panel Center Trim Panel Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
2. Remove the HVAC control module screws.
3. Remove the HVAC control module.
4. Remove the HVAC control module wire harness connectors.

Installation Procedure

1. Install the HVAC control module wire harness connectors.
2. Install the HVAC control module.
3. Tighten the HVAC control module screws. Tighten: Tighten the screws to 2.5 N.m (22 lb in).
4. Install the I/P center trim panel. Refer to «Instrument Panel Center Trim Panel Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
5. Start the engine and let run for one minute.
6. Refer to «Control Module References»(/chevrolet/malibu/vi-2006-2008/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for programming and setup information.

1. Remove the right closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
2. Remove the blower motor control processor wire harness connector.
3. Remove the blower motor control processor screws.
4. Remove the blower motor control processor.

1. Install the blower motor control processor.
2. Tighten the blower motor control processor screws. Tighten: Tighten the blower motor resistor screws to 1.5 N.m (13 lb in).
3. Install the blower motor control processor wire harness connector.
4. Install the right closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .

1. Remove the fuse labeled HVAC CTRL (BATT).
2. Remove the right closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
3. Remove the communication interface module. Refer to «Communication Interface Module Replacement»(/chevrolet/malibu/vi-2006-2008/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system) .
4. Remove the OnStar module bracket. Refer to «Bracket Assembly Replacement - OnStar Module»(/chevrolet/malibu/vi-2006-2008/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system) .
5. Remove the recirculation door actuator screws.
6. Remove the recirculation door actuator.
7. Remove the recirculation door actuator wire harness connector.

1. Install the recirculation door actuator wire harness connector.
2. Install the recirculation door actuator.
3. Tighten the recirculation door actuator screws. Tighten: Tighten the screws to 1.5 N.m (13 lb in).
4. Install the OnStar module bracket. Refer to «Bracket Assembly Replacement - OnStar Module»(/chevrolet/malibu/vi-2006-2008/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system) .
5. Install the communication interface module. Refer to «Communication Interface Module Replacement»(/chevrolet/malibu/vi-2006-2008/remont/entertainment-systems/#cellular-system-entertainment-system-and-navigation-system) .
6. Install the right closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
7. Install the fuse labeled HVAC CTRL (BATT).

1. Remove the fuse labeled HVAC CTRL (BATT).
2. Completely open instrument panel (I/P) compartment door by pressing both tabs that support the stop bumpers. Refer to «Instrument Panel Compartment Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
3. Remove the mode actuator wire harness connector.
4. Remove the mode actuator screws.
5. Remove the mode actuator.

1. Install the mode actuator.
2. Install the mode actuator screws. Tighten: Tighten the screws to 1.5 N.m (13 lb in).
3. Install the mode actuator wire harness connector.
4. Close I/P compartment door. Refer to «Instrument Panel Compartment Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
5. Install the fuse labeled HVAC CTRL (BATT).

1. Remove the fuse labeled HVAC CTRL (BATT).
2. Remove the left closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Left Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
3. Remove the knee bolster. Refer to «Knee Bolster Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
4. Remove the air temperature actuator screws.
5. Remove the air temperature actuator.
6. Remove the air temperature actuator wire harness connector.

1. Install the air temperature actuator wire harness connector.
2. Install the air temperature actuator.
3. Tighten the air temperature actuator screws. Tighten: Tighten the screws to 1.5 N.m (13 lb in).
4. Install the knee bolster. Refer to «Knee Bolster Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
5. Install the left closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Left Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
6. Install the fuse labeled HVAC CTRL (BATT).

1. Remove the left closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Left Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
2. Remove the knee bolster. Refer to «Knee Bolster Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
3. Twist and pull the upper air temperature sensor from the upper right air outlet duct.
4. Remove the upper air temperature sensor wire harness connector.

1. Install the upper air temperature sensor wire harness.
2. Install the upper air temperature sensor.
3. Install the knee bolster. Refer to «Knee Bolster Replacement»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
4. Install the left closeout panel. Refer to «Instrument Panel Insulator Panel Replacement - Left Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .

1. Remove the right console trim panel. Refer to «Front Floor Console Side Trim Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .
2. Twist and pull the lower air temperature sensor from the center floor air outlet duct.
3. Remove the lower air temperature sensor wire harness.

1. Install the lower air temperature sensor wire harness.
2. Install the lower air temperature sensor.
3. Install the right console trim panel. Refer to «Front Floor Console Side Trim Panel Replacement - Right Side»(/chevrolet/malibu/vi-2006-2008/remont/exteriorinterior-trim/#instrument-panel-trim-and-console-trim) .

Air Delivery Description and Operation

The air delivery controls are divided into 4 areas

1. HVAC control components
2. Air speed
3. Air distribution
4. Recirculation operation
5. Automatic operation

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from °C to °F by pressing the Auto button for a minimum of 3 seconds. The ignition 3 voltage circuit provides a device on signal. The control module supports the following features

Air Delivery Description and Operation

Mode/Recirculation Actuator

The mode or recirculation actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.

Mode Valve Assembly

The film valve system has several operating characteristics

1. The cycle time for a mode change will vary based on the starting point of the film valve relative to the requested mode position.
2. The maximum time to achieve a mode change occur when the film valve travels between vent and defrost.
3. Mode change times may very slightly based on variations in system airflow, temperature and voltage.
4. The amount of air rush noise heard when a mode change is requested that causes the film valve to move through three or more primary modes is dependent on blower speed.
5. Recalibration will typically occur when the engine is OFF. The actuator noise heard during recalibration may be more noticeable than during normal operation.

Blower Motor Control Processor

The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

Air Speed

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position. The blower motor will only operate if the blower motor switch is in any position other than OFF, and the ignition switch is in the RUN position.

Once a blower speed is selected, the blower speed remains constant until a new speed is selected.

As the requested blower speed increases, the following conditions occur

1. The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.
2. The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.

As the requested blower speed decreases, the following conditions occur

1. The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.
2. The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.

Afterblow

Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned off. This reduces the amount of microbial growth that can create undesirable odors. The vehicle does not come equipped with the afterblow feature turned on. If the afterblow feature is required due to an odor concern, it must be turned on by the scan tool.

The following conditions must be met for afterblow to operate

1. The A/C compressor operated for more than 10 seconds.
2. The A/C compressor, after operating for more than 10 seconds has not been deactivated for more than 10 minutes.
3. The system voltage is at least 11 volts to start and 10 volts to continue to run.
4. The ignition has been in the OFF position for at least 20 minutes.

Once the above conditions have been met the following sequence of events will occur

1. The blower will run for 4 minutes at 59 percent blower speed.
2. The recirculation door moves to outside air position.
3. The mode valve moves to the floor position.

Air Distribution

The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet. The mode switch provides the vehicle operator with the ability to override the automatic setting. When the mode switch is moved to the bi-level through defrost positions, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. When VENT is pressed, the following will occur

1. The mode valve will be moved to the panel position.
2. The recirculation actuator will follow user request if blower is on and power mode is in run.
3. The A/C compressor will follow user request if blower is on and power mode is in run.

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in bi-level through defrost. The operator must activate the blower for Recirculation operation.

Automatic Operation

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in automatic mode, the following is required

1. The blower motor switch must be in the AUTO position.
2. The air temperature switch must be in any other position other than 60 or 90 degrees.
3. The mode switch must be in the AUTO position.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Regulate blower motor speed
2. Position the air temperature actuator
3. Position the mode actuator
4. Position the recirculation actuator
5. Request A/C operation

When the warmest position is selected in automatic operation the blower speed will increase gradually until the vehicle reaches normal operating temperature. When normal operating temperature is reached the blower will stay on high speed and the air temperature actuators will stay in the full heat position. When the coldest position is selected in automatic operation the blower will stay on high and the air temperature actuators will stay in the full cold position.

In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. The vehicle operator can select an extreme temperature setting but the system will not warm the vehicle any faster. In warm temperatures, the automatic HVAC system will also provide air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

Remote Vehicle Start HVAC Operation

The HVAC preset RVS settings are as follows

1. Inside air temperature input below 22°C (72°F) the HVAC system will set the blower motor speed to high speed, set the mode door to the defrost position, set the temperature door to the full hot position and set the recirculation door to the outside air position.
2. Inside air temperature input above 26°C (79°F) the HVAC system will set the blower motor speed to high speed, set the mode door to the panel position, set the temperature door to the full cold position, request A/C compressor operation and set the recirculation door to the recirculate position.
3. Inside air temperature input between 22°C (72°F) and 26°C (79°F) the HVAC system will set the blower motor speed to a medium speed, set the mode door to the panel position, set the temperature door to the full cold position, request A/C compressor operation and set the recirculation door to the outside air position.

When you transition from remote start to normal operation (by entering car, inserting key and turning on) the C68 control head reverts to the prior remote start function settings.

Air Temperature Description and Operation

The air temperature controls are divided into four primary areas

1. Radio - Driver Information Center (DIC)
2. Automatic operation
3. The Heating and Air Conditioning System
4. The A/C cycle

Radio Display

This vehicle is equipped with a driver information center and it displays outside temperature through the radio display. If an outside temperature display concern occurs please refer to Outside Air Temperature Display Inaccurate or Inoperative .

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from °C to °F by pressing the Auto button for a minimum of 3 seconds. The HVAC control module during defrost modes will change the A/C compressor LED status from on to off. The ignition 3 voltage circuit provides a device on signal. The control module supports the following features

Air Temperature Description and Operation

Air Temperature Actuators

The air temperature actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.

Air Temperature Sensors

The air temperature sensors are 2-wire negative temperature co-efficient thermistors. The vehicle uses the following air temperature sensors

1. Ambient
2. Inside
3. Upper duct air temperature sensor
4. Lower duct air temperature sensor

A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal decreases as the resistance decreases. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts.

The inside air temperature sensor is located within the HVAC control module. Replacement of this sensor involves the replacement of the HVAC control module. The inside air temperature sensor operates within a temperature range between -40 to +185°C (-40 to +365°F). If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. The ambient temperature sensor operates within a temperature range between -40 to +87.5°C (-40 to +189.5°F). The sensor signal is read by the BCM, scaled appropriately and transmitted to the HVAC Control Module through the Low Speed bus. If the sensor is shorted to ground, voltage, or an open, the system will operate using a signal scaled appropriately to allow the system to operate.

The duct temperature sensor temperature response is different from the ambient and inside sensors. A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases the sensor resistance decreases. The sensor operates within a temperature range between -40 to +80°C (-40 to +176°F).

Sunload Sensor

The sunload sensor is a 2-wire photo diode. The vehicle uses a single sunload sensor. The sensor is integrated into the ambient light sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The sensor signal is read by the BCM, scaled appropriately and transmitted to the HVAC control module through the GM LAN Low Speed bus. Bright, or high intensity, light causes the vehicles inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

A/C Refrigerant Pressure Sensor

The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts.

The A/C refrigerant pressure sensor prevents the A/C system from operating when an excessively high or low pressure condition exists.

If the powertrain control module (PCM) or engine control module (ECM) detects a failure in the A/C refrigerant pressure sensor or A/C High Side Pressure sensor circuit, the GM LAN Low Speed bus message sent to the HVAC control module will be invalid.

The afterblow function is not enabled from the factory. To enable function the following must occur. As soon as ignition is turned off, and all active processes are complete, the controller is put into sleep or low power mode. A high voltage wakeup is generated on the low speed GMLAN by the body control module (BCM) and the HVAC virtual network is activated. Embedded in GMLAN message is Afterblow control logic bit (Aftrblw_Active). The afterblow resides in the BCM. The BCM has a timer that tells the HVAC Control module to go to Hi blower. The HVAC afterblow function is used to eliminate the odor associated with A/C usage. The "After Blow" is a method where by the HVAC blower is run for a few minutes after the vehicle is turned OFF in order to physically blow off excess condensation and eliminate odors.

Heating and A/C Operation

The purpose of the heating and A/C system is to provide the following

1. Heated air
2. Cooled air
3. Remove humidity from the interior of the vehicle
4. Reduce windshield fogging

Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve a desired temperature

1. Recirculation actuator setting
2. Difference between inside and desired temperature
3. Difference between ambient and desired temperature
4. Blower motor speed setting
5. Mode setting

The HVAC control module commands or monitors the following actions when an air temperature setting is selected.

1. Warmest position-The air temperature actuator door position directs maximum air flow through the heater core.
2. Coldest position-The air temperature actuator door position directs maximum air flow around the heater core.

Between the warmest and coldest position-The following sensors are monitored to direct the appropriate amount of air through the heater core to achieve the desired temperature

1. Sunload
2. Ambient temperature
3. Inside temperature
4. Lower duct temperature
5. Upper duct temperature

The A/C system is engaged by selecting the A/C or auto switches for the blower motor and the mode switch on the HVAC control module. The HVAC control module sends a A/C request message to the powertrain control module (PCM) or engine control module (ECM) for A/C compressor clutch operation. The following conditions must be met in order for the PCM/ECM to turn on the compressor clutch

1. HVAC control module Evaporator temperature is more than 4°C (39°F). The control module operating range is 9-16 volts.
2. PCM/ECM Engine coolant temperature (ECT) is less than 114°C (237°F). Engine RPM is between 0-5,000 RPM. A/C pressure is between 2997 kPa (435 psi) and 248 kPa (36 psi).

Once engaged, the compressor clutch will be disengaged for the following conditions

1. Throttle position is 100 percent.
2. A/C pressure is more than 2997 kPa (435 psi).
3. A/C pressure is less than 248 kPa (36 psi).
4. ECT is more than 120°C (248°F).
5. Engine speed is more than 5,000 RPM.
6. Transmission shift
7. The PCM/ECM detects excessive torque load.
8. The PCM/ECM detects insufficient idle quality.
9. The PCM/ECM detects a hard launch condition.

When the compressor clutch disengages, the compressor clutch diode protects the electrical system from a voltage spike.

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in automatic mode, the following is required

1. The blower motor switch must be in the AUTO position.
2. The air temperature switch must be in any other position other than 60 or 90 degrees.
3. The mode switch must be in the AUTO position.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Regulate blower motor speed
2. Position the air temperature actuator
3. Position the mode actuator
4. Position the recirculation actuator
5. Request A/C operation

When the warmest position is selected in automatic operation the blower speed will increase gradually until the vehicle reaches normal operating temperature. When normal operating temperature is reached the blower will stay on high speed and the air temperature actuators will stay in the full heat position. When the coldest position is selected in automatic operation the blower will stay on high and the air temperature actuators will stay in the full cold position.

In cold temperatures, the automatic HVAC system will provide heat in the most efficient manner. The vehicle operator can select an extreme temperature setting but the system will not warm the vehicle any faster. In warm temperatures, the automatic HVAC system will also provide air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

The HVAC preset RVS settings are as follows

1. Inside air temperature input below 22°C (72°F) the HVAC system will set the blower motor speed to high speed, set the mode door to the defrost position, set the temperature door to the full hot position and set the recirculation door to the outside air position.
2. Inside air temperature input above 26°C (79°F) the HVAC system will set the blower motor speed to high speed, set the mode door to the panel position, set the temperature door to the full cold position, request A/C compressor operation and set the recirculation door to the recirculate position.
3. Inside air temperature input between 22°C (72°F) and 26°C (79°F) the HVAC system will set the blower motor speed to a medium speed, set the mode door to the panel position, set the temperature door to the full cold position, request A/C compressor operation and set the recirculation door to the recirc air position.

When you transition from remote start to normal operation (by entering car, inserting key and turning on) the HVAC control head reverts to the prior remote start function settings.

Engine Coolant

Engine coolant is the key element of the heating system. The engine thermostat controls the normal engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation. Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC module. The ambient air drawn through the HVAC module absorbs the heat of the coolant flowing through the heater core. The HVAC module distributes heated air to the passenger compartment for consistent passenger comfort. Opening or closing the HVAC module temperature door controls the amount of heat delivered to the passenger compartment. The coolant exits the heater core through the return heater hose and is recirculated back through the engine cooling system.

A/C Cycle

Refrigerant is the key element in an air conditioning system. R-134a is presently the only EPA approved refrigerant for automotive use. R-134a is an very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

The A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the discharge hose, and forced to flow to the condenser and then through the balance of the A/C system. The A/C system is mechanically protected with the use of a high pressure relief valve. If the high pressure switch were to fail or if the refrigerant system becomes restricted and refrigerant pressure continued to rise, the high pressure relief will pop open and release refrigerant from the system.

Compressed refrigerant enters the condenser in a high temperature, high pressure vapor state. As the refrigerant flows through the condenser, the heat of the refrigerant is transferred to the ambient air passing through the condenser. Cooling the refrigerant causes the refrigerant to condense and change from a vapor to a liquid state.

The condenser is located in front of the radiator for maximum heat transfer. The condenser is made of aluminum and aluminum cooling fins, which allows rapid heat transfer for the refrigerant. The semi-cooled liquid refrigerant exits the condenser and flows through the liquid line, to the thermal expansion valve.

The thermal expansion valve is located in the liquid line between the condenser and the evaporator. The thermal expansion valve is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the thermal expansion valve, the pressure of the refrigerant is lowered. Due to the pressure differential of the liquid refrigerant, the refrigerant will begin to vaporize at the thermal expansion valve. The thermal expansion valve also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the thermal expansion valve flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC module and passes through the evaporator core. Warm and moist air will cause the liquid refrigerant boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator back through the thermal expansion valve and into the suction line and back to the compressor, in a vapor state completing the A/C cycle of heat removal. At the compressor, the refrigerant is compressed again and the cycle of heat removal is repeated.

The conditioned air is distributed through the HVAC module for passenger comfort. The heat and moisture removed from the passenger compartment will also change form, or condense, and is discharged from the HVAC module as water under the vehicle.

Special Tools

Special Tools Illustration Tool Number/Description J 43600 ACR 2000 Air Conditioning Service Center

Scheme 61

See also:
• DTC Symptom Description
• Testing for Intermittent Conditions and Poor Connections
• Diagnostic System Check - Vehicle
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Control Module References
• Ambient Light Sensor Replacement
• HVAC Connector End Views
• HVAC Compressor Clutch Does Not Disengage
• Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
• Symptoms - Vehicle
• Checking Aftermarket Accessories
• Leak Testing
• Defrosting Insufficient
• Noise Diagnosis - Blower Motor
• Noise Diagnosis - Air Conditioning (A/C) System
• Odor Diagnosis
• Noise Diagnosis - HVAC Module
• Engine Overheating
• Air Conditioning (A/C) System Performance Test
• Compressor Clutch Assembly Replacement
• Diagnostic Trouble Code (DTC) List - Vehicle
• Instrument Panel Center Trim Panel Replacement
• Fastener Notice
• Communication Interface Module Replacement
• Outside Air Temperature Display Inaccurate or Inoperative
• DTC B0164, B0174, or B0179
• Air Delivery Description and Operation
• Air Temperature Description and Operation
• HVAC Compressor Clutch Does Not Disengage
• Blower Motor Always On
• Blower Motor Inoperative
• Blower Motor Malfunction
• Re-Calibrating Actuators
• Sensor Resistance Table (Ambient Air Temp Sensor)
• Sensor Resistance Table (Duct Temp conversion temp to counts)
• Sensor Resistance Table (Inside Air Temperature Sensor)
• Sensor Resistance Table (Upper and Lower Duct Temp Sensors)