HVAC Systems - Automatic Buick Rendezvous I

Fastener Tightening Specifications

Fastener Tightening Specifications

Sensor Resistance Table (Outside Air Temperature)

Sensor Resistance Table (Outside Air Temperature)

Sensor Resistance Table (Evaporator Temperature)

Sensor Resistance Table (Evaporator Temperature)

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

HVAC Connector End Views

A/C Compressor Clutch Connector End Connector Part Information 15326801 2-Way F GT 150 Series (LT GRY) Pin Wire Color Circuit No. Function A DK GRN 59 A/C Compressor Clutch Supply Voltage B BLK 1050 Ground

A/C Refrigerant Pressure Sensor Connector End Connector Part Information 12110192 3-Way F Metri-Pack 150 Series (BLK) Pin Wire Color Circuit No. Function A BLK 2751 Low Reference B GRY 2700 5-Volt Reference C RED/BLK 380 A/C Refrigerant Pressure Sensor Signal

Air Temperature Actuator Connector End - Left Connector Part Information 12064978 6-Way F Micro-Pack 100 Series (GRY) Pin Wire Color Circuit No. Function 1 BRN 241 Ignition 3 Voltage 2 DK BLU 1199 Left Air Temperature Door Control 3 BLK 150 Ground 4 - - Not Used 5 LT BLU 733 Left Air Temperature Door Position Signal 6 GRY 598 5-Volt Reference

Air Temperature Actuator Connector End - Right Connector Part Information 12064993 6-Way F Micro-Pack 100 Series (BLK) Pin Wire Color Circuit No. Function 5 BRN 241 Ignition 3 Voltage 6 WHT/BLK 1236 Right Air Temperature Door Control 7 BLK 150 Ground 8 - - Not Used 9 DK BLU 1646 Right Air Temperature Door Position Signal 10 GRY 598 5-Volt Reference

Blower Motor Connector End Connector Part Information 12084957 2-Way F Metri-Pack 280 Series (BLK) Pin Wire Color Circuit No. Function A RED - Blower Motor Supply Voltage B BLK - Ground

Blower Motor Control Processor Connector End Connector Part Information 12105056 4-Way F (BLK) Pin Wire Color Circuit No. Function 1 RED 442 Battery Positive Voltage 2 ORN 761 Blower Motor Speed Signal 3 GRY/BLK 754 Blower Motor Speed Control 4 BLK 150 Ground

Evaporator Temperature Sensor Connector End Connector Part Information 12052832 2-Way F Metri-Pack 150 Series (BLK) Pin Wire Color Circuit No. Function A WHT 2622 Evaporator Temperature Sensor Signal B BLK 552 Low Reference

HVAC Control Module Connector End Connector Part Information 12110206 24-Way F Micro-Pack 100 Series (LT BLU) Pin Wire Color Circuit No. Function A1 BLK 552 Low Reference A2 - - Not Used A3 WHT 2622 Evaporator Temperature Sensor Signal A4 LT BLU/BLK 590 Sunload Sensor Signal A5-A6 - - Not Used A7 GRY/BLK 754 Blower Motor Speed Control A8 ORN 761 Blower Motor Speed Signal A9 - - Not Used A10 BLK 150 Ground A11 BRN 241 Ignition 3 Voltage A12 ORN 640 Battery Positive Voltage B1 DK BLU 1646 Right Air Temperature Door Position Signal B2 LT BLU 733 Left Air Temperature Door Position Signal B3 YEL/BLK 713 Mode Door Position Signal B4 GRY 598 5-Volt Reference B5 WHT/BLK 1236 Right Air Temperature Door Control B6 DK BLU 1199 Left Air Temperature Door Control B7 TAN 2273 Mode Door Control B8 TAN/BLK 2274 Recirculation Door Control B9 WHT 1038 Class 2 Serial Data B10 - - Not Used B11 WHT 193 Rear Defog Relay Control B12 GRY 8 Instrument Panel Lamp Supply Voltage

Mode Actuator Connector End Connector Part Information 12064993 6-Way F Micro-Pack 100 Series (BLK) Pin Wire Color Circuit No. Function 5 BRN 241 Ignition 3 Voltage 6 TAN 2273 Mode Door Control 7 BLK 150 Ground 8 - - Not Used 9 YEL/BLK 713 Mode Door Position Signal 10 GRY 598 5-Volt Reference

Recirculation Actuator Connector End Connector Part Information 12064993 6-Way F Micro-Pack 100 Series (BLK) Pin Wire Color Circuit No. Function 5 BRN 241 Ignition 3 Voltage 6 TAN/BLK 2274 Recirculation Door Control 7 BLK 150 Ground 8-10 - - Not Used

Sunload Sensor Connector End Connector Part Information 15316639 2-Way F (BLK) Pin Wire Color Circuit No. Function 1 LT BLU/BLK 590 Sunload Sensor Signal 2 BLK 552 Low Reference

Test Description

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

1. 3: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 5: Determine if the HVAC Control Module, Body Control Module or Powertrain Control Module have set DTCs which may affect HVAC operation are present.
3. 6: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
4. 7: Answer Yes if the first 3 characters of the DTC name begins with B10; regardless of the last 2 characters.

Diagnostic System Check - HVAC Systems - Automatic

Scan Tool Output Controls

HVAC Control Module Scan Tool Output Controls

PCM Scan Tool Output Controls

Scan Tool Data List

BCM Scan Tool Data List

HVAC Control Module Scan Tool Data List

PCM Scan Tool Data List 3.4L (LA1)

ECM Scan Tool Data List 3.6L (LY7)

Scan Tool Data Definitions

The HVAC Scan Tool Data Definitions contain a brief description of all the scan tool parameters. This list is in alphanumeric order.

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

The HVAC control module monitors the passenger compartment inside air temperature through an inside air temperature sensor. The inside air temperature sensor is a integral part of the HVAC control module. When the air is cold, the sensor resistance and the signal voltage are high. When the air is warm, the sensor resistance and the signal voltage are low.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

1. The HVAC control module detects the signal circuit is less than 0.09 volts.
2. The HVAC control module detects the signal circuit is more than 4.90 volts.

Action Taken When the DTC Sets

1. The DTC is stored in DTC information.
2. The HVAC control module will continue to monitor the reference signal of the inside air temperature sensor.

Conditions for Clearing the DTC

1. The DTC will become history if the HVAC control module no longer detects a condition.
2. The history DTC clears after 50 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 in Wiring Systems.

DTC B0165 or B0166

The mode actuator is an electronic device that incorporates a stepper motor and feedback potentiometer. The HVAC control module controls the mode door position by sending a control signal to the actuator. The signal's value is dependent upon the desired mode selected by the vehicle occupants. As the actuator moves, the potentiometer produces the actual door position signal that is sent to the HVAC control module. The HVAC control module continues to command the actuator to move until the desired and actual values are equal. The door directs airflow through the outlets as selected by the vehicles occupants.

The HVAC control module commands the actuator through it's full range. The HVAC control module stores the learned minimum and maximum position values. The travel range value is calculated by subtracting the minimum and maximum position values. Then the HVAC control module compares the travel range, minimum and maximum values to calibrated value ranges. If the travel range value 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. The HVAC control module continuously compares the actual actuator position to the calibrated minimum and maximum position values.

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

1. Mode actuator position signal is less than 5 counts.
2. Mode actuator position signal is more than 194 counts.
3. The mode actuators total travel range is less than or greater than the calibrated limits.

1. The DTC is stored in DTC information.
2. The HVAC control module will continue to make use of whatever travel range is still available.

1. If the HVAC control no longer detects a failure, then the DTC will become history.
2. The history DTC will clear after 50 ignition cycles without a failure.
3. The DTC can be cleared with a scan tool.

1. A damaged or broken mode door and or actuator can cause this DTC to set.
2. If the Mode actuator travels beyond it's calibrated limits the DTC will set.

DTC B0233

The HVAC control module commands the air temperature actuator movement with one of three voltage signals applied to the air temperature door control circuit. A low voltage of 0 volts moves the air temperature door toward full hot. A voltage of 2.5 volts stops the actuator. A high voltage of 5 volts moves the air temperature door toward full cold. The HVAC control module determines the current position of the actuator by monitoring the feedback voltage of the air temperature door position signal circuit. The feedback potentiometer position is a function of the actuator position. A high voltage indicates a full cold air temperature door position. A low voltage indicates a full hot air temperature door position. The HVAC control module controls the air temperature door position in order to maintain the selected air temperature.

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

1. The air temperature position signal is less than 5 counts.
2. The air temperature position signal is greater than 194 counts.
3. The air temperature actuator actual total travel range max-min is less than or greater than the range limits.

1. The HVAC control module will continue to make use of whatever air temperature actuator travel range is still available.
2. The DTC is stored in DTC information.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 50 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. A damaged or broken air temperature actuator or mode door can cause this DTC to set.
2. If the condition is not present refer to «Testing for Intermittent Conditions and Poor Connections»(/buick/rendezvous/i-2001-2007/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor) in Wiring Systems.

DTC B0408 or B0418

The HVAC control module monitors the temperature of the refrigerant through the evaporator via a evaporator temperature sensor. When the refrigerant temperature is low the sensor resistance and the signal voltage are high. When the refrigerant temperature is high the sensor resistance and the signal voltage are low. The sensor works in conjunction with a switch to meter the flow of refrigerant therefore preventing the freezing of moisture that condenses on the evaporator. An evaporator with too little refrigerant will starve causing insufficient cooling. An evaporator flooded with refrigerant will also cause poor cooling when there is too much liquid refrigerant that cannot vaporize quickly.

The ignition is turned ON.

The HVAC control module detects the signal circuit is less than 5 counts (0.09 volts).

1. The HVAC control module will store the trouble code in memory.
2. A default value will be used for the sensor data by the HVAC control module to allow the A/C system to operate.

1. The DTC will become history if the HVAC control module no longer detects a failure.
2. The history DTC will clear after 50 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

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: Tests for the proper operation of the circuit in the high voltage range.
2. 4: 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 B3933

The powertrain control module (PCM) or engine control module (ECM) monitors the high side refrigerant pressure via a air conditioning (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 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.

DTC Descriptor

This diagnostic procedure supports the following DTCs

1. DTC P0530 Air Conditioning (A/C) Refrigerant Pressure Sensor Signal Circuit Too Low or Too High
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. A/C has been requested.

1. The PCM/ECM detects the signal circuit is less than 5 counts (0.09 volt) or more than 250 counts (4.90 volts).
2. The condition exists for 20 seconds.

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 DTC will become history if the PCM 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.

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. 4: If the pressure signal voltage stays high after disconnecting the pressure sensor electrical connector, the signal circuit is shorted to voltage, or the PCM/ECM is faulty.
2. 7: Tests for a high resistance or for an open in the ground circuit.
3. 16: This vehicle is equipped with a PCM/ECM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). Before you replace the PCM, program the new PCM/ECM.

DTC P0530, P0532, or P0533

DTC P0645, P0646, or P0647: Air Conditioning (A/C) Clutch Relay Control Circuit

Ignition voltage is supplied directly to the air conditioning (A/C) compressor clutch relay. The powertrain control module (PCM) or engine control module (ECM) controls the relay by grounding the control circuit of the A/C clutch relay through an internal solid state device. This device is called a driver. The driver supplies the ground for the component that is being controlled. Each driver has a fault line which is monitored by the PCM/ECM. When the PCM/ECM commands a component ON, the voltage of the control circuit should be near 0 volts. When the PCM/ECM commands the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses an unexpected voltage, this DTC will set.

The PCM/ECM will monitor the control circuit to the A/C clutch relay for the following conditions

1. A short to ground
2. A short to voltage
3. An open circuit
4. An open relay coil
5. A relay coil that is shorted internally or which has a very low resistance

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

This diagnostic procedure supports the following DTCs

1. DTC P0645 The PCM/ECM detects an open on the control circuit of the A/C compressor clutch relay.
2. DTC P0646 The PCM/ECM detects a short to ground on the control circuit of the A/C compressor clutch relay.
3. DTC P0647 The PCM/ECM detects a short to voltage on the control circuit of the A/C compressor clutch relay.

The ignition voltage is between 9-18 volts.

1. A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit to the A/C clutch relay.
2. The condition is present for at least 30 seconds.

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

1. A history DTC will clear after 50 consecutive fault free ignitions have occurred without a malfunction.
2. The DTC can be cleared by using a scan tool.

If DTC P0645, P0646, or P0647 cannot be duplicated, review the Failure Records. Observe the vehicle mileage since the diagnostic test last failed. This may help to determine how often the condition which 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 relay operates. Command the ON and the OFF states. Repeat the commands as necessary.
2. 12: The PCM/ECM utilizes Electrically Erasable Programmable Read Only Memory (EEPROM). Program the new PCM/ECM before you replace the PCM/ECM.

DTC P0645, P0646, or P0647

1. Perform the «Diagnostic System Check - HVAC Systems - Automatic»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic) 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»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic__air-delivery-description-and-operation) «Air Temperature Description and Operation»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-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»(/buick/rendezvous/i-2001-2007/remont/body-electrical/#wiring-systems-diagnostic-information-and-procedures__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. 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»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-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 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 (LA1 / 3.4L)»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic) or «HVAC Compressor Clutch Does Not Engage (LY7 / 3.6L)»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic)
2. «HVAC Compressor Clutch Does Not Disengage»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic__hvac-compressor-clutch-does-not-disengage)
3. «Blower Motor Always On»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic__blower-motor-always-on)
4. «Blower Motor Inoperative»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic__blower-motor-inoperative)
5. «Blower Motor Malfunction»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic)
6. «Too Hot in Vehicle»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic)
7. «Too Cold in Vehicle»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic)
8. «Air Delivery Improper»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic)
9. «Air Recirculation Malfunction»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#hvac-systems-automatic__air-recirculation-malfunction)
10. «Leak Testing»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__leak-testing) in Heating, Ventilation and Air Conditioning
11. «Defrosting Insufficient»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__defrosting-insufficient) in Heating, Ventilation and Air Conditioning
12. «Noise Diagnosis - Blower Motor»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-blower-motor) in Heating, Ventilation and Air Conditioning
13. «Noise Diagnosis - Air Conditioning (A/C) System»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-air-conditioning-ac) in Heating, Ventilation and Air Conditioning
14. «Odor Diagnosis»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__odor-diagnosis) in Heating, Ventilation and Air Conditioning
15. «Noise Diagnosis - HVAC Module»(/buick/rendezvous/i-2001-2007/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-hvac-module) in Heating, Ventilation and Air Conditioning
16. «Outside Air Temperature Display Inaccurate or Inoperative»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console

The Mitsubishi scroll type air conditioning (A/C) compressor carries an internal thermal cut off switch. The thermal cut off switch normal operation is to open and disable the compressor under extreme load and temperatures above 155°C (311°F). The internal thermal cut off switch is non-serviceable.

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 (ECT) is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.

1. 3: Pressing the center of the left side driver temperature control switch and setting 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 (LA1 / 3.4L)

The Mitsubishi scroll type air conditioning (A/C) compressor carries an internal thermal cut off switch. The thermal cut off switch normal operation is to open and disable the compressor under extreme load and temperatures above 155°C (311°F). The internal thermal cut off switch is non-serviceable.

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 (ECT) is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.

1. 3: Pressing the center of the left side driver temperature control switch and setting 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 (LY7 / 3.6L)

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 speed control circuit should steadily increase from 0 V to 8.0 V as the blower speed is adjusted from the minimum speed position to the maximum speed position.

Blower Motor Malfunction

The Mitsubishi scroll type A/C compressor carries an internal thermal cut off switch. The thermal cut off switch normal operation is to open and disable the compressor under extreme load and temperatures above 155°C (311°F). The internal thermal cut off switch is non-serviceable.

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

1. 7: This test is to ensure A/C system is operating normally.
2. 10: The aspirator tube connects to the rear of the HVAC control module. The aspirator tube is used to draw air past the inside air temperature sensor.

Too Hot in Vehicle

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

1. 3: This checks for A/C compressor clutch always on.
2. 7: This test is to insure cooling system is operating normally.
3. 10: The aspirator tube connects to the rear of the HVAC control module. The aspirator tube is used to draw air past the inside air temperature sensor.

Too Cold in Vehicle

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

1. 3: This step tests for a blower motor that does not operate regardless of the desired blower motor speed.
2. 4: This step tests for a blower motor that operates, yet does not accurately respond to the desired blower motor speed.
3. 5: The HVAC control module is inoperative when the it does not respond to any operator requests. This step verifies that there is power to the HVAC control assembly.
4. 13: The voltage will vary between 0-5 volts during normal operation. The HVAC control assembly connector must be connected during this step.

Air Delivery Improper

Air Recirculation Malfunction

Air Recirculation Malfunction

Removal Procedure

1. Remove the I/P cluster trim plate bezel. Refer to «Trim Plate Bezel Replacement - Instrument Panel (I/P) Cluster (Aztek)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) or «Trim Plate Bezel Replacement - Instrument Panel (I/P) Cluster (Rendezvous)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Remove the HVAC control module retaining screws.
3. Pull the HVAC control module out from the I/P.
4. Disconnect the aspirator hose (1) from the HVAC control module.
5. Disconnect the electrical connector from the HVAC control module.
6. Remove the HVAC control module.

Installation Procedure

1. Connect the electrical connector to the HVAC control module.
2. Connect the aspirator hose (1) to the HVAC control module.
3. Install the HVAC control module to the I/P.
4. Install the HVAC control module retaining screws. Tighten: Tighten the screws to 2.5 N.m (22 lb in).
5. Install the I/P cluster trim plate bezel. Refer to «Trim Plate Bezel Replacement - Instrument Panel (I/P) Cluster (Aztek)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) or «Trim Plate Bezel Replacement - Instrument Panel (I/P) Cluster (Rendezvous)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages, and Console.

1. Remove the right side I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Disconnect the blower motor electrical connector.
3. Remove the blower motor mounting screws.
4. Remove the blower motor from the HVAC module assembly.
5. Disconnect the electrical connector from the blower motor control processor assembly.
6. Remove the forward blower control processor mounting screws.
7. Remove the rearward blower control processor mounting screw.
8. Remove the blower control processor assembly from the HVAC module assembly.

1. Install the blower motor control processor assembly to the HVAC module assembly.
2. Install the rearward mounting screw. Tighten: Tighten the screw to 1.8 N.m (16 lb in).
3. Install the forward mounting screws. Tighten: Tighten the screws to 1.8 N.m (16 lb in).
4. Connect the electrical connector to the blower control processor assembly.
5. Install the blower motor to the HVAC module assembly.
6. Install the blower motor mounting screws. Tighten: Tighten the screws to 1.8 N.m (16 lb in).
7. Connect the blower motor electrical connector.
8. Install the right side I/P insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

1. Remove the upper I/P trim pad. Refer to «Trim Pad Replacement - Instrument Panel (I/P) Upper (Aztek)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) or «Trim Pad Replacement - Instrument Panel (I/P) Upper (Rendezvous)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Disconnect the recirculation actuator electrical connector.
3. Remove the mounting screws from the recirculation actuator.
4. Remove the recirculation actuator.

1. Install the recirculation actuator.
2. Install the recirculation actuator mounting screws. Tighten: Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the recirculation actuator electrical connector.
4. Install the upper I/P trim pad. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

1. Remove the knee bolster from the instrument panel (I/P). Refer to «Knee Bolster Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Disconnect the mode actuator electrical connector.
3. Open the mode actuator push rod retainer clip (1) with a small flat-bladed screwdriver.
4. Disconnect the mode actuator push rod (2) from the retainer clip (1).
5. Disconnect the I/P wiring harness clip from the I/P support bracket.
6. Remove the mode actuator mounting screws.
7. Remove the mode door actuator.

1. Install the mode actuator.
2. Install the mode actuator mounting screws. Tighten: Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the I/P wiring harness clip to the I/P support bracket.
4. Connect the mode actuator push rod (2) to the retainer clip (1).
5. Close the push rod retainer clip (1).
6. Connect the mode actuator electrical connector.
7. Install the knee bolster. Refer to «Knee Bolster Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

1. Remove the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Disconnect and remove the right hand temperature door lever spring (2).
3. Disconnect and remove the right hand temperature lever (1) from the right hand temperature door.
4. Disconnect the right hand temperature actuator electrical connector.
5. Remove the right hand temperature actuator mounting screws.
6. Remove the right hand temperature actuator.

1. Install the right hand temperature actuator.
2. Install the right hand temperature actuator mounting screws. Tighten: Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the right hand temperature actuator electrical connector.
4. Install the right hand temperature lever (1) to the right hand temperature door.
5. Connect the right hand temperature door lever spring (2) to the right hand temperature door lever (1) and HVAC module case.
6. Install the I/P compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

1. Remove the knee bolster. Refer to «Knee Bolster Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Set the HVAC controls to the vent mode to position the defroster door lever.
3. Remove the left hand temperature door lever bolt (3) from the HVAC module.
4. Disconnect and remove the left hand temperature door lever spring (2).
5. Disconnect and remove the left hand temperature door lever (1) from the left hand temperature door.
6. Disconnect the left hand air temperature actuator electrical connector.
7. Remove the left hand air temperature actuator mounting screws.
8. Remove the left hand air temperature actuator.

1. Install the left hand air temperature actuator.
2. Install the left hand air temperature actuator mounting screws. Tighten: Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the left hand air temperature actuator electrical connector.
4. Install the left hand temperature door lever (1) to the left hand temperature door.
5. Connect the left hand temperature door lever spring (2) to the left hand temperature door lever (1) and HVAC module case.
6. Install the left hand temperature door lever bolt (3) to the HVAC module case. Tighten: Tighten the bolt to 0.9 N.m (8 lb in).
7. Install the knee bolster. Refer to «Knee Bolster Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

1. Remove the I/P carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.
2. Remove the aspirator hose mounting screw.
3. Disconnect the aspirator hose from the aspirator duct adapter (1).
4. Remove the aspirator hose from the HVAC module.

1. Install the aspirator hose to the HVAC module.
2. Install the aspirator hose retaining screw. Tighten: Tighten the screw 0.9 N.m (8 lb in).
3. Connect the aspirator hose to the aspirator duct adapter (1).
4. Install the I/P carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/buick/rendezvous/i-2001-2007/remont/gauges-instrument-panels/#instrument-panel-system-displays-gauges-and-console) in Instrument Panel, Gages and Console.

Tools Required

J 38778 Door Trim Pad Clip Remover

1. Open the hood.
2. Disconnect the electrical connector from the ambient air temperature sensor.
3. Use J 38778 to disconnect the wiring harness retainer which secures the ambient air temperature sensor to the hood latch support.
4. Remove the ambient air temperature sensor from the wiring harness retainer.
5. Remove the ambient air temperature sensor from the vehicle.

1. Install the ambient air temperature sensor on the wiring harness retainer.
2. Install the wiring harness push-in retainer which secures the ambient air temperature sensor to the hood latch support.
3. Connect the electrical connector to the ambient air temperature sensor.

1. Remove the windshield garnish molding. Refer to «Garnish Molding Replacement - Windshield Pillar»(/buick/rendezvous/i-2001-2007/remont/exteriorinterior-trim/#interior-trim) in Interior Trim.
2. Lift the I/P upper trim panel up approximately 51 mm (2 in) and pull rearward to release I/P upper trim panel retainers.
3. Lift the I/P upper trim panel to access sun load sensor.
4. Disconnect the sunload sensor electrical connector.
5. Remove the sun load sensor.

1. Install sun load sensor.
2. Connect the sunload sensor electrical connector.
3. Align the I/P upper trim locating pins and the retainers to the slots in the I/P.
4. Push forward and down on the I/P upper trim panel to lock into place.
5. Install the windshield garnish molding. Refer to «Garnish Molding Replacement - Windshield Pillar»(/buick/rendezvous/i-2001-2007/remont/exteriorinterior-trim/#interior-trim) in Interior Trim.

Air Delivery Description and Operation

The air delivery description and operation is divided into five areas

1. HVAC Control Components
2. Air Speed
3. Air Delivery
4. Recirculation Operation
5. Automatic 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 body control module (BCM), which is the vehicle mode master, provides a device on signal. The control module supports the following features

Air Delivery Description and Operation

Mode Actuator

The mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5 volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5 volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.

The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

Recirculation Actuator

The recirculation actuator is a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit is either grounded or opened during normal operation. If the control circuit is grounded, then the shaft rotates in the opposite direction than it would if the circuit was opened. The actuator shaft rotates until the limit is reached. If the module needs to reverse the direction of rotation, then the control circuit's state is reversed. The open circuits are held at ignition 3 voltage from the actuator. The module will maintain the control circuit's state until a new position is needed.

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, Blower motor speed signal, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module sends the commanded blower motor speed to the control processor through a 0 to 12-volt linear ramped blower motor speed control circuit. As the blower motor speed control voltage increases, the blower motor speed increases. The control processor sends the actual blower speed to the control module through a 0 to 12-volt blower motor speed signal circuit. The processor supplies 12volts 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 or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.

OFF Mode

Press the passenger temperature knob to turn off the HVAC control module. When the vehicle is moving, air flowing over the vehicle increases the air pressure just ahead of the windshield. This forces air into the ambient air into the HVAC module and out through the floor and windshield outlets. Since the A/C compressor is not running, the incoming air may be warmed but not cooled. Recirculation is not adjustable in OFF mode.

Purge Operation

If the ambient air temperature is less than 2 C (35 F) and the coolant temperature is less than 10 C (50 F), then a 75-second purge will occur. The purge will begin as soon as the coolant temperature reaches 4 C (40 F). The mode door will move to the defrost position and the blower motor will be near half speed.

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 door is moved to the defrost position, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. Regardless of the mode setting, a small amount of air will be diverted to the defrost ducts to reduce windshield fogging. This vehicle may be equipped with a passenger compartment air filter. When VENT is pressed, the following will occur

1. The recirculation actuator will be placed in the outside air position
2. The A/C compressor will be commanded off
3. The mode is adjustable

After a malfunction occurs to the mode actuator it is driven to the Defrost position. On startup, the HVAC control module will place the mode door in the last selected position.

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is only available when the HVAC control module is in Panel or Bi-level. The recirculation mode will stay on and the recirculation indicator will illuminate until either outside air or a non-recirculation mode is selected. When the recirculation actuator sees an open in the control circuit, the actuator will default to the recirculation position.

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 you must set the temperature and press the drivers temperature knob. Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Monitor the following sensors: Inside air temperature sensor Ambient air temperature sensor Sunload sensor
2. Regulate blower motor speed
3. Position the air temperature actuator
4. Position the mode actuator
5. Position the recirculation actuator
6. Request A/C operation

Air Temperature Description and Operation

The air temperature controls are divided in 5 primary areas

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

The HVAC control module works in a dual role operating both air temperature and A/C operation from the drivers side switch. 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 body control module (BCM), which is the vehicle mode master, provides a device on signal. For information on the BCM serial data messages and discrete signals. Refer to Body Control System Description and Operation in Body Control System. The control module supports the following features

Air Temperature Description and Operation

Air Temperature Actuator

The air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3-voltage, low reference control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

Inside Air Temperature Sensor

Replacement of the inside air temperature sensor means replacing the HVAC control module. The inside air temperature sensor is an integral part of the HVAC control module. The HVAC control module monitors the passenger compartment inside air temperature through an inside air temperature sensor. When the air is cold, the sensor resistance and the signal voltage are high. When the air is warm, the sensor resistance and the signal voltage are low. The HVAC control module requests A/C compressor clutch engagement and controls the air temperature actuator door positions in order to maintain the selected air temperature. The HVAC control module sends out a 5-volt reference signal to the inside air temperature sensor over the 5-volt reference circuit. A thermistor varies the reference voltage back to the HVAC control module through the low reference circuit.

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 2979 kPa (432 psi). The clutch will be enabled after the pressure decreases to less than 1510 kPa (219 psi).
2. A/C pressure is less than 186 kPa (27 psi). The clutch will be enabled after the pressure increases to more than 207 kPa (30 psi).

Evaporator Temperature Sensor

The A/C System is protected by the evaporator temperature sensor. The sensor located on the evaporator core provides the HVAC control module with the surface temperature of the evaporator core. If the evaporator temperature sensor reads a temperature of 0°C (32°F), the HVAC control module will turn off the A/C compressor clutch until evaporator temperatures reach 2°C (36°F).

Ambient Air Temperature Sensor

The ambient air temperature sensor is a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors

1. Ambient
2. Inside

A 5-volt reference and signal 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 of -40°C (-40°F) to 60°C (140°F). The HVAC control module receives a class 2 message from the instrument panel cluster (IPC). The ambient air temperature sensor is mounted in the forward engine area of the vehicle. In this position, it is exposed to the airflow through the grill before it reaches the radiators. The sensor signal varies between 0 to 5 volts. The HVAC control module converts the signal to a working temperature range.

If the HVAC control module detects a faulty class 2 signal, then the control module software will use a defaulted air temperature value.

The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the system is fixed.

The ambient air temperature is updated and displayed under the following conditions

Air Temperature Description and Operation

Sunload Sensor

The sunload sensor is a 2-wire photo diode. Low reference and signal circuits enable the sensor to operate. As the light shining upon the sensor gets brighter, the sensor conductance increases. The sensor signal decreases as the conductance increases. 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 a measurement of the amount of light shining on the vehicle. 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. If the HVAC control module detects a malfunctioning sensor, then the control module software will use a defaulted sunload valve. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is fixed. A resistance check of the sunload sensor should not be performed as it will damage the sensor.

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 control module makes the following actions when automatic operation is not selected, and an air temperature setting is selected

1. When the air temperature switch is placed in the warmest position, the control module commands the air temperature door to divert maximum air past the heater core.
2. When the air temperature switch is placed in the coldest position, the control module commands the air temperature door to direct air to bypass the heater core.
3. When the air temperature switch is placed between the warmest and coldest positions, the control module monitors the following sensor inputs to determine the air temperature door position that diverts the appropriate amount of air through the heater core in order to achieve the desired temperature: Sunload Ambient temperature Inside temperature

The following shows what blower motor, recirculation actuator, and mode actuator adjustments are made for each air temperature switch selection

The A/C system can be engaged by either pressing the driver temperature switch or during automatic operation. The A/C display will illuminate on the HVAC control module display board when the driver temperature switch is pressed. The control module sends a class 2 A/C request message to the powertrain control module (PCM). The HVAC system uses a scroll compressor that incorporates a thermal switch that opens once the compressor temperature is more than 155°C (311°F). The thermal switch is a non-serviceable item. The following conditions must be met in order for the PCM to turn on the compressor clutch

1. HVAC control module Ambient temperature more than 0°C (32°F) Evaporator Temperature more than 2°C (36°F)
2. BCM Battery voltage between 9-16 volts A/C request from the HVAC control module
3. PCM Engine coolant temperature (ECT) is less than 125°C (257°F) Engine RPM is below 5000 RPM A/C Pressure is between 1510-2979 kPa (219-432 psi)

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

1. Compressor thermal switch is opened
2. Throttle position is 100 percent
3. A/C Pressure is more than 2979 kPa (432 psi)
4. A/C Pressure is less than 1510 kPa (219 psi)
5. Engine coolant temperature (ECT) is more than 125°C (257°F)
6. Engine speed is more than 5500 RPM
7. Transmission shift
8. PCM detects excessive torque load
9. PCM detects insufficient idle quality
10. PCM detects a hard launch

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

Dual Zone Operation

The HVAC control module uses dual rotary temperature switches. The dual zone controls allows for maximum temperature offset and comfort between the driver and passenger. It is possible to select maximum airflow over the evaporator core with one dual zone switch along with maximum airflow over the heater core with the other dual zone switch. Each air temperature actuator is independent from the other and the passenger side is not limited in it's range of temperature offset.

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 you must set the temperature and press the drivers temperature knob. Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Monitor the following sensors: Inside air temperature sensor Ambient air temperature sensor Sunload sensor
2. Regulate blower motor speed
3. Position the air temperature actuator
4. Position the mode actuator
5. Position the recirculation actuator
6. Request A/C operation

Engine Coolant

Engine coolant is the essential element of the heating system. The thermostat controls the normal operating temperature of the engine. 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 a very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

A Mitsubishi scroll 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. 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 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 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 through the suction line and back to the compressor, in a vapor state, and 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.

Special Tools

Special Tools Illustration Tool Number/Description J 34142-B Test Light J 35616-A Connector Test Adapter Kit J 38778 Door Trim Pad Clip Remover J 39200 Digital Multimeter J 43600 ACR 2000 Air Conditioning Service Center 7000081 Tech 2 Kit

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

See also:
• Diagnostic Starting Point - Heating, Ventilation and Air Conditioning
• Scan Tool Does Not Power Up
• Power Mode Mismatch
• Diagnostic Trouble Code (DTC) List
• Diagnostic Trouble Code (DTC) List
• Diagnostic Trouble Code (DTC) List
• Testing for Intermittent Conditions and Poor Connections
• Circuit Testing
• Wiring Repairs
• Connector Repairs
• HVAC Schematics
• HVAC Connector End Views
• HVAC Compressor Clutch Does Not Disengage
• Powertrain Control Module (PCM) Replacement
• Engine Control Module (ECM) Replacement
• Checking Aftermarket Accessories
• Leak Testing
• Defrosting Insufficient
• Noise Diagnosis - Blower Motor
• Noise Diagnosis - Air Conditioning (A/C) System
• Odor Diagnosis
• Noise Diagnosis - HVAC Module
• Outside Air Temperature Display Inaccurate or Inoperative
• Engine Coolant Temperature Indicator Always On
• Heating Performance Diagnostic
• Garnish Molding Replacement - Windshield Pillar
• Symptoms - HVAC Systems - Automatic
• Diagnostic Trouble Code (DTC) List
• DTC P0645, P0646, or P0647
• 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
• Air Recirculation Malfunction