HVAC Systems - Manual Buick LaCrosse I

Fastener Tightening Specifications

Fastener Tightening Specifications

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

HVAC Connector End Views

A/C Compressor Clutch Connector Part Information OEM: 12162017 Service: 12101937 2-Way F Metri-Pack 150 Series Sealed (MD-GY) Pin Wire Color Circuit No. Function A D-GN 59 A/C Compressor Clutch Supply Voltage B BK 1050 Ground

A/C Refrigerant Pressure Sensor Connector Part Information OEM: 15344137 Service: 15306432 3-Way F GT 150 Series Flexlock Sealed (BK) Pin Wire Color Circuit No. Function 1 BK 2751 Low Reference 2 GY 2700 5-Volt Reference 3 RD/BK 380 A/C Refrigerant Pressure Sensor Signal

Air Temperature Actuator Connector Part Information OEM: 12059110 Service: 88953271 2-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function A D-BU 1646 Air Temperature Door Control B B D-BU 1646 Air Temperature Door Control A

Blower Motor Connector Part Information OEM: 12084957 Service: 12126461 2-Way F Metri-Pack 280 Series (BK) Pin Wire Color Circuit No. Function A PU 65 Blower Motor Supply Voltage B BK 2150 Ground

Blower Motor Control Processor Connector Part Information OEM: 12041429 Service: 12167129 5-Way F Metri-Pack 280 Series (BK) Pin Wire Color Circuit No. Function A BK 1450 Ground B GY/BK 754 Blower Motor Speed Control C RD 442 Battery Positive Voltage D BK 2150 Ground E PU 65 Blower Motor Supply Voltage

HVAC Control Module Connector Part Information OEM: 12110206 Service: 12110206 24-Way F Micro-Pack 100 Series (L-BU) Pin Wire Color Circuit No. Function A1 - - Not Used A2 OG 1040 Battery Positive Voltage A3 PK 739 Ignition 1 Voltage A4 - - Not Used A5 BK/WH 1551 Ground A6-A8 - - Not Used A9 D-BU 1646 Air Temperature Door Control B A10 D-BU 1646 Air Temperature Door Control A A11 L-GN/BK 1647 Recirculation Door Control B A12 PK/WH 1648 Recirculation Door Control A B1 - - Not Used B2 WH 1038 HVAC Class 2 Serial Data B3-B4 - - Not Used B5 GY 8 Instrument Panel Lamp Supply Voltage B6 BK 1450 Ground B7-B8 - - Not Used B9 GY/BK 754 Blower Motor Speed Control B10 TN 2273 Mode Door Control B B11 L-GN 2275 Mode Door Control A B12 - - Not Used

Mode Actuator Connector Part Information OEM: 12047781 Service: 12101864 3-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function A TN 2273 Mode Door Control B B - - Not Used C L-GN 2275 Mode Door Control A

Recirculation Actuator Connector Part Information OEM: 12059110 Service: 88953271 2-Way F Metri-Pack 150 Series (BK) Pin Wire Color Circuit No. Function A L-GN/BK 1647 Recirculation Door Control B B PK/WH 1648 Recirculation Door Control A

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Scan Tool Output Controls

PCM Scan Tool Output Controls

Scan Tool Data List

Use the Scan Tool Data Display Values and Definitions Information in order to assist in diagnosing the HVAC system. 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 problem 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).

PCM Scan Tool Data List

Scan Tool Data Definitions

The HVAC Scan Tool Data Definitions contains a brief description of all HVAC related parameters available on the scan tool. The list is in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together.

Circuit Description

The HVAC control module controls the HVAC actuators to regulate the airflow through the HVAC system. Each 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. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. 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 limited and more that or equal to the minimum calibrated limit, then the calibration is considered successful.

1. Air Flow Control 3 Circuit refers to the mode actuator.
2. Air Flow Control 7 Circuit refers to the recirculation actuator.
3. Temperature Control 2 Circuit refers to the temperature actuator.

DTC Descriptors

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 B0418 Temperature Control 2 Circuit

Conditions for Running the DTC

The HVAC control module has completed a calibration/recalibration of the actuator.

Conditions for Setting the DTC

The HVAC control module does not detect any movement of the actuator after 2 unsuccessful attempts at moving the actuator.

Action Taken When the DTC Sets

The HVAC control module will recalibrate the appropriate actuator each time the ignition switch is turned ON.

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 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

Diagnostic Aids

1. Inspect the appropriate actuator door and actuator for the following conditions: A misaligned actuator-Refer to the following: «Air Temperature Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Mode Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Recirculation Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) 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»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) in Wiring Systems.
3. Actuator inoperative DTCs typically occur with actuator performance DTCs. Diagnose and repair an actuator inoperative DTC before diagnosing an actuator performance DTC. The actuator performance DTCs are as follows: B0424 B3748 B3749

Test Description

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

1. 3: This step drives the actuator in one direction. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
2. 4: This step drives the actuator in the opposite direction.

DTC B0248, B0268 Or B0418

The HVAC control module controls the HVAC actuators to regulate the airflow through the HVAC system. Each 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. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. 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 limited and more that or equal to the minimum calibrated limit, then the calibration is considered successful.

1. Air Flow Control 3 Circuit Range/Performance refers to the mode actuator.
2. Air Flow Control 7 Circuit Range/Performance refers to the recirculation actuator.
3. Temperature Control 2 Circuit refers to the air temperature actuator.

This diagnostic procedure supports the following DTCs

1. DTC B0249 Air Flow Control 3 Circuit Range/Performance
2. DTC B0269 Air Flow Control 7 Circuit Range/Performance
3. DTC B0419 Temperature Control 2 Circuit

The HVAC control module has completed 2 calibration/recalibration events of the actuators.

DTC P0560 is not set.

1. The HVAC control module will substitute a default range value.
2. The HVAC control module will no longer issue commands to the actuator if its run timer expires during the calibration/recalibration event.

The HVAC control module will substitute a default range value.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. Inspect the appropriate actuator door and actuator for the following conditions: A misaligned actuator-Refer to the following: «Air Temperature Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Mode Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Recirculation Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) 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»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) in Wiring Systems.

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

1. 3: This step drives the actuator in one direction. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
2. 4: This step drives the actuator in the opposite direction.

DTC B0249, B0269 Or B0419

The HVAC control module controls the HVAC actuators to regulate the airflow through the HVAC system. Each 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. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. 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 limited and more that or equal to the minimum calibrated limit, then the calibration is considered successful.

1. Temperature Control 2 Feedback Circuit Range/Performance refers to the temperature actuator.
2. Air Flow Control 3 Feedback Circuit Range/Performance refers to the mode actuator.
3. Air Flow Control 7 Feedback Circuit Range/Performance refers to the recirculation actuator.

This diagnostic procedure supports the following DTCs

1. DTC B0424 Temperature Control 2 Feedback Circuit Range/Performance
2. DTC B3748 Air Flow Control 3 Feedback Circuit Range/Performance
3. DTC B3749 Air Flow Control 7 Feedback Circuit Range/Performance

The HVAC control module has performed an actuator index.

DTC P0560 is not set.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. Inspect the appropriate actuator door and actuator for the following conditions: A misaligned actuator-Refer to the following: «Air Temperature Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Mode Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) «Recirculation Actuator Replacement»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) 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»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing) in Wiring Systems.

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

1. 3: This step drives the actuator in one direction. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
2. 4: This step drives the actuator in the opposite direction.

DTC B0424, B3748 Or B3749

The engine control module (ECM)/powertrain control module (PCM) monitors the high side refrigerant pressure via the A/C refrigerant pressure sensor. The ECM/PCM applies 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 ECM/PCM 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 ECM/PCM commands the cooling fans on. When pressure is too high or too low the ECM/PCM will not allow the A/C compressor clutch to engage. When the DTC is set, the ECM/PCM does not allow the A/C compressor clutch to engage. This is done to protect the compressor.

This diagnostic procedure supports the following DTCs

1. DTC P0530 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit
2. DTC P0532 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage
3. DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage

1. The engine is running.
2. The A/C is requested.

P0530

The A/C refrigerant pressure sensor signal voltage is less than 0.2 volt or more than 4.88 volts for more than 3 seconds.

P0532

The A/C refrigerant pressure sensor signal voltage is less than 0.2 volt for more than 3 seconds.

P0533

The A/C refrigerant pressure sensor signal voltage is more than 4.88 volts for more than 3 seconds.

1. The ECM/PCM stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The ECM/PCM disables the A/C compressor clutch.
4. The ECM/PCM records the operating conditions at the time the diagnostic fails. The ECM/PCM stores this information in the Failure Records.
5. The ECM/PCM will report a value of 0 kPa to the HVAC control module.
6. The driver information center will display SERVICE A/C SYSTEM.
7. The A/C OFF segment will illuminate on the HVAC control module.

1. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
2. The current DTC will clear when the diagnostic runs and does not fail.
3. Use a scan tool in order to clear the diagnostic trouble code.

If DTC P0532 or P0533 cannot be duplicated, reviewing the Failure Records vehicle mileage 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 in Wiring Systems.

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

1. 3: This step tests for the proper operation of the circuit in the low voltage range.
2. 4: 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. 5: This step tests for a short to voltage in the 5-volt reference circuit.

DTC P0530, P0532 Or P0533

Ignition voltage is supplied directly to the A/C compressor clutch relay. The engine control module (ECM)/powertrain control module (PCM) 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 ECM/PCM. When the ECM/PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts. When the ECM/PCM 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 ECM/PCM 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 ECM/PCM detects any of the above malfunctions, this DTC is set and the affected driver is disabled.

This diagnostic procedure supports the following DTCs

1. DTC P0645 Air Conditioning (A/C) Clutch Relay Control Circuit
2. DTC P0646 Air Conditioning (A/C) Clutch Relay Control Circuit Low Voltage
3. DTC P0647 Air Conditioning (A/C) Clutch Relay Control Circuit High Voltage

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

P0645

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

P0646

The ECM/PCM detects a short to ground on the control circuit of the A/C compressor clutch relay.

P0647

The ECM/PCM detects a short to voltage on the control circuit of the A/C compressor clutch relay.

1. The ECM/PCM will not illuminate the malfunction indicator lamp (MIL).
2. The ECM/PCM 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 DTC P0645, P0646, P0647 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 in Wiring Systems.

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 engine control module is providing ground to the A/C compressor clutch relay. If light always on circuit 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, P0646 Or P0647

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(/buick/lacrosse/i-2004-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) in Wiring Systems.
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. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__air-temperature-description-and-operation) .
5. 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
6. 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 in Wiring Systems.

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»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual)
2. «HVAC Compressor Clutch Does Not Disengage»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__hvac-compressor-clutch-does-not-disengage)
3. «Blower Motor Always On»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__blower-motor-always-on)
4. «Blower Motor Inoperative»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__blower-motor-inoperative)
5. «Blower Motor Malfunction»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual)
6. «Too Hot in Vehicle»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__too-hot-in-vehicle)
7. «Too Cold in Vehicle»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__too-cold-in-vehicle)
8. «Air Delivery Improper»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual__air-delivery-improper)
9. «Leak Testing»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning) in Heating, Ventilation and Air Conditioning
10. «Defrosting Insufficient»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__defrosting-insufficient) in Heating, Ventilation and Air Conditioning
11. «Noise Diagnosis - Blower Motor»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-blower-motor) in Heating, Ventilation and Air Conditioning
12. «Noise Diagnosis - Air Conditioning (A/C) System»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-air-conditioning-ac) in Heating, Ventilation and Air Conditioning
13. «Noise Diagnosis - HVAC Module»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-hvac-module) in Heating, Ventilation and Air Conditioning
14. «Odor Diagnosis»(/buick/lacrosse/i-2004-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__odor-diagnosis) in Heating, Ventilation and Air Conditioning

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 124°C (255°F).

1. 3: Placing the fan switch in the ON position, along with placing the air temperature control switch in a cold setting, activates A/C operation. For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.
2. 6: The HVAC control module is inoperative when the module does not respond to any operator control requests to enable the A/C compressor. The blower motor may still operate independent of the A/C controls.

HVAC Compressor Clutch Does Not Engage

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

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

1. 2: This step will determine if one or more blower speeds are inoperative.
2. 3: This step determines if the HVAC control module and blower motor control processor are attempting to control the blower motor speed.
3. 5: The measured voltage on the blower motor speed control circuit should steadily decrease from 4.6 V to 1.1 V as the blower motor speed is adjusted from the minimum speed position to the maximum speed position.

Blower Motor Malfunction

Too Hot In Vehicle

Too Hot In Vehicle

Too Cold In Vehicle

Too Cold In Vehicle

Air Delivery Improper

Air Delivery Improper

Calibration Procedure

Use the following steps to perform the calibration update

1. Turn OFF the ignition.
2. Remove the battery positive voltage circuit fuse of the HVAC Control Module.
3. Wait 60 seconds.
4. Install the fuse.

Removal Procedure

1. Remove the instrument panel lower trim plate. Refer to «Trim Plate Replacement - Instrument Panel (I/P) Lower (w/Floor Console)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the HVAC control assembly mounting screws (1).
3. Pull the HVAC control assembly rearward from the instrument panel.
4. Disconnect the electrical connectors form the HVAC control assembly.
5. Remove the HVAC control assembly.

Installation Procedure

1. Connect the electrical connectors to the HVAC control assembly.
2. Install the HVAC control assembly.
3. Install the HVAC control assembly mounting screws. Tighten: Tighten the screws to 2 N.m (18 lb in).
4. Install the instrument panel lower trim plate. Refer to «Trim Plate Replacement - Instrument Panel (I/P) Lower (w/Floor Console)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
5. Start the engine and run for 1 minute.

1. Remove the right side instrument panel (I/P) insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Remove the screws retaining the air temperature actuator (2).
4. Disconnect the electrical connector from the air temperature actuator.
5. Remove the air temperature actuator from the HVAC Module Assembly.

1. Position the air temperature actuator (2). Align the slots in the electric actuator driver to the flats on the shaft.
2. Align the locating hole to the alignment pin on the HVAC module case.
3. Slide the actuator driver on the shaft. The actuator driver should sit completely on the shaft and the mounting holes should be flush with the HVAC module case.
4. Install the screws to the air temperature actuator. Tighten: Tighten the screw to 1.5 N.m (13 lb in).
5. Connect the electrical connector to the air temperature actuator.
6. Install the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
7. Install the right side I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
8. Calibrate the actuator. Refer to «Re-Calibrating Actuators»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) .

1. Remove the right instrument panel (I/P) insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Remove the screws that secure the mode actuator (1) to the HVAC module assembly.
4. Remove the mode actuator from the HVAC module assembly.
5. Disconnect the electrical connector from the mode actuator.

1. Position the mode actuator, aligning the slots in the electric actuator drive to the flats on the shaft.
2. Align the locating hole to the alignment pin on the HVAC module assembly.
3. Slide the actuator drive completely onto the shaft, with the mounting holes flush with the mounting screw holes on the HVAC module assembly.
4. Install the screws to the mode actuator (1). Tighten: Tighten the screws to 1.5 N.m (13 lb in).
5. Connect the electrical connector to the mode actuator.
6. Install the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
7. Install the right I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
8. Calibrate the actuator. Refer to «Re-Calibrating Actuators»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) .

1. Remove the right instrument panel (I/P) insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Remove the screws that secure the recirculation actuator to the HVAC module assembly.
4. Remove the recirculation actuator from the HVAC module assembly.
5. Disconnect the electrical connector from the recirculation actuator.

1. Position the recirculation actuator, aligning the slots in the electric actuator drive to the flats on the shaft.
2. Align the locating hole to the alignment pin on the HVAC module assembly.
3. Slide the actuator drive completely onto the shaft, with the mounting holes flush with the mounting screw holes on the HVAC module assembly.
4. Install the screws to the recirculation actuator. Tighten: Tighten the screws to 1.5 N.m (13 lb in).
5. Connect the electrical connector to the recirculation actuator.
6. Install the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
7. Install the right/I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/lacrosse/i-2004-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
8. Calibrate the actuator. Refer to «Re-Calibrating Actuators»(/buick/lacrosse/i-2004-2009/remont/manual-hvac-system/#hvac-systems-manual) .

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

HVAC Control Module

The HVAC control module is a Class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. 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, all HVAC DTCs and settings will be erased from KAM. The control module supports the following features

Air Delivery Description and Operation

Mode/Recirculation Actuator

The mode/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 to 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 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 vehicle's interior. The vehicle operator determines the blower motor's 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, with the exception of afterblow.

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 heater 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 heater through defrost. The operator must activate the blower for Recirculation operation.

Remote Start Activation

The following describes the HVAC control head functionality upon receiving the remote start active serial data message and a power mode status is set to off a wake. intake air temperature (IAT) on manual systems, are utilized to determine the moding of the following features: Blower Mode (Bi-level, floor, Defrost, Recirc and rear Defrost. These features as determined by the IAT during activation sequence and are maintained for the duration of engine run time. Calibratable temperatures are utilized to provide low, mid and high temperature ranges for feature selectable. Blower and mode have the range to select any valid feature positions. When the remote start active serial data is received ignition-off loop HVAC algorithms will act the same as if a run power mode received (i.e. re-calibration, After blow, ignition-off motor positioning etc.) off timer and ignition on timer have the functionality as in Run mode.

Remote Start De-activation

When the remote start is exited (class 2 power mode = run mode or remote start engine), In the case of manual settings, displays will revert to actual state of operation of the features on the basis of their normal control algorithms.

Air Temperature Description and Operation

The air temperature controls are divided into 4 areas

1. HVAC Control Components
2. Heating and A/C Operation
3. Engine Coolant
4. A/C Cycle

The HVAC control module is a Class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. 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, all HVAC DTCs and settings will be erased from KAM. The control module supports the following features

Air Temperature Description and Operation

Air Temperature Actuator

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-volt 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.

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 protects the A/C system from operating when an excessively high or low pressure condition exists. The PCM disables the compressor clutch under the following conditions

1. A/C pressure is more than 3034 kPa (440 psi). The clutch will be enabled after the pressure decreases to less than 2068 kPa (300 psi).
2. A/C pressure is less than 241 kPa (35 psi). The clutch will be enabled after the pressure increases to more than 248 kPa (36 psi).

Heating and A/C Operation

The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature switch. Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve the 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 A/C system can be engaged by either pressing the A/C switch or by selecting the following modes

1. Max A/C
2. Heater
3. Mix-Blend
4. Front Defrost

The A/C LED will not illuminate unless the driver presses the A/C request switch on the HVAC control module. Otherwise, the A/C system may be running without the A/C LED indicator illuminated. The following conditions must be met in order for the powertrain control module (PCM) to turn on the compressor clutch

1. The ambient air temperature is above 4°C (40°F).
2. The engine coolant temperature (ECT) is less than 124°C (255°F).
3. The A/C pressure is between 241-3034 kPa (35-440 psi).

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

1. The throttle position is 100%.
2. The A/C pressure is more than 3034 kPa (440 psi).
3. The A/C pressure is less than 241 kPa (35 psi).
4. The engine coolant temperature (ECT) is more than 124°C (255°F).
5. The engine speed is more than 5480 RPMs for at least 409 seconds.
6. A transmission shift has occurred.
7. The PCM detects excessive torque load.
8. The PCM detects insufficient idle quality.
9. The PCM detects a hard launch condition.

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

The following describes the HVAC control head functionality upon receiving the remote start active serial data message and a power mode status is set to off a wake. intake air temperature (IAT) on manual systems, are utilized to determine the moding of the following features: Blower Mode (Bi-level, floor, Defrost, Recirc and rear Defrost. These features as determined by the IAT during activation sequence and are maintained for the duration of engine run time. Calibratable temperatures are utilized to provide low, mid and high temperature ranges for feature selectable. Blower and mode have the range to select any valid feature positions. When the remote start active serial data is received ignition-off loop HVAC algorithms will act the same as if a run power mode received (i.e. re-calibration, After blow, ignition-off motor positioning etc.) off timer and ignition on timer have the functionality as in Run mode.

When the remote start is exited (class 2 power mode = run mode or remote start engine), In the case of manual settings, displays will revert to actual state of operation of the features on the basis of their normal control algorithms.

Engine Coolant

Engine coolant is the key element of the heating system. The thermostat controls 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 assembly. The heat of the coolant flowing through the heater core is absorbed by the ambient air drawn through the HVAC module assembly. Heated air is distributed to the passenger compartment through the HVAC module assembly for passenger comfort.

The amount of heat delivered to the passenger compartment is controlled by opening or closing the air temperature door. The coolant exits the heater core through the return heater hose and recirculates 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 a very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

A Delphi model CVC7 piston type compressor is used on this model year vehicle. The A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant, which adds heat to the refrigerant. The refrigerant is discharged from the compressor through the discharge hose and is 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 continues 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 tubing 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 TXV.

The TXV is located at the evaporator inlet. The TXV is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the TXV, the pressure on the refrigerant is lowered. Due to the pressure differential on the liquid refrigerant, the refrigerant will begin to boil at the TXV. The TXV also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the TXV 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 causes the liquid refrigerant to 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 through the suction line and back to the compressor in a vapor state and completes 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 condenses and is discharged from the HVAC module as water.

Special Tools

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

Scheme 6

See also:
• Testing for Intermittent Conditions and Poor Connections
• Diagnostic System Check - Vehicle
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• Control Module References
• Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
• Checking Aftermarket Accessories
• Defrosting Insufficient
• Noise Diagnosis - Blower Motor
• Noise Diagnosis - Air Conditioning (A/C) System
• Noise Diagnosis - HVAC Module
• Odor Diagnosis
• Engine Overheating (LY7)
• Heating Performance Diagnostic
• Trim Plate Replacement - Instrument Panel (I/P) Lower (w/Floor Console)
• Fastener Notice
• DTC B0248, B0268 or B0418
• HVAC Connector End Views
• Air Delivery Description and Operation
• Air Temperature Description and Operation
• HVAC Compressor Clutch Does Not Disengage
• Blower Motor Always On
• Blower Motor Inoperative
• Too Hot in Vehicle
• Too Cold in Vehicle
• Air Delivery Improper