HVAC Systems - Automatic Cadillac SRX I

Fastener Tightening Specifications

Fastener Tightening Specifications

Sensor Resistance Table

Sensor Resistance Table

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

HVAC Connector End Views

A/C Compressor Clutch Connector Part Information 7282-5548-30 2-Way M Yazaki Weather Pack (BK) Pin Wire Color Circuit No. Function 1 D-GN 59 A/C Compressor Clutch Supply Voltage 2 BK 750 Ground (LY7) BK 1550 Ground (LH2)

A/C Refrigerant Pressure Sensor Connector Part Information 12186689 3-Way F Metri-Pack 150 Series, Sealed, P2S (BK) Pin Wire Color Circuit No. Function A TN 452 Low Reference (LY7) TN 470 Low Reference (LH2) B GY 596 5-Volt Reference (LY7) GY 2700 5-Volt Reference (LH2) C OG/BK 380 A/C Refrigerant Pressure Sensor Signal

Air Temperature Actuator - Left Connector Part Information IL-AG5-7S-S3C1 7-Way F Molex (L-GN) Pin Wire Color Circuit No. Function 1 GY 705 5-Volt Reference 2 - - Not Used 3 YE 61 Low Reference 4 - - Not Used 5 L-BU 733 Driver Air Temperature Door Position Signal 6 D-BU 1199 Driver Air Temperature Door Control B 7 YE 1791 Driver Air Temperature Door Control A

Air Temperature Actuator - Right Connector Part Information IL-AG5-7S-S3C1 7-Way F Molex (L-GN) Pin Wire Color Circuit No. Function 1 YE 61 Low Reference 2 - - Not Used 3 GY 705 5-Volt Reference 4 - - Not Used 5 D-BU 1646 Passenger Air Temperature Door Position 6 GY/BK 2778 Passenger Air Temperature Door Control A 7 WH/BK 1236 Passenger Air Temperature Door Control B

Ambient Air Temperature Sensor Connector Part Information 7283-7028-30 2-Way F Yazaki 2.3 Series, Sealed (BK) Pin Wire Color Circuit No. Function 1 L-GN/BK 735 Ambient Air Temperature Sensor Signal 2 YE 61 Low Reference

Scheme 24

Blower Motor - Auxiliary Connector Part Information 6098-0325 2-Way F Sumitomo (WH) Pin Wire Color Circuit No. Function 1 OG 1052 Auxiliary Blower Motor Supply Voltage 2 PU 65 Blower Motor Supply Voltage

Blower Motor Resistor Assembly - Auxiliary Connector Part Information 6098-0514 4-Way F Sumitomo (WH) Pin Wire Color Circuit No. Function 1 OG 1052 Auxiliary Blower Motor Supply Voltage 2 TN 63 Blower Motor Medium 1 Control 3 L-BU 72 Medium 2 Blower Motor Control 4 YE 60 Blower Motor Low Control

Blower Motor Connector Part Information 7283-3020-30 2-Way F Yazaki (BK) Pin Wire Color Circuit No. Function 1 PU 374 Auxiliary Blower Motor Speed Control 2 L-BU 188 Blower Motor Control Processor Supply Voltage

Blower Motor Control Module Connector Part Information 6098-1449 4-Way F Sumitomo (BK) Pin Wire Color Circuit No. Function 1 PU 374 Auxiliary Blower Motor Speed Control 2 L-BU 188 Blower Motor Control Processor Supply Voltage 3 GY/BK 754 Blower Motor Speed Control 4 BK 450 Ground

Blower Motor Switch - Auxiliary Connector Part Information 12015416 8-Way F Metri-Pack 280 Series (WH) Pin Wire Color Circuit No. Function A BK 1050 Ground B PU/WH 5264 Rear Auxiliary Mode Door Control C BK 1050 Ground D YE 60 Blower Motor Low Control E TN 63 Blower Motor Medium 1 Control F L-BU 72 Medium 2 Blower Motor Control G OG 1052 Auxiliary Blower Motor Supply Voltage H YE 1491 Backlight Lamps Control

Blower Motor Switch - Rear Auxiliary Connector Part Information 12015416 8-Way F Metri-Pack 280 Series (WH) Pin Wire Color Circuit No. Function A BK 1050 Ground B - - Not Used C PU/WH 5264 Rear Auxiliary Mode Door Control D YE 60 Blower Motor Low Control E TN 63 Blower Motor Medium Control F L-BU 72 Medium 2 Blower Motor Control G OG 1052 Auxiliary Blower Motor Supply Voltage H YE 1491 Backlight Lamps Control

Evaporator Temperature Sensor Connector Part Information 7123-2820 2-Way F Yazaki (CL) Pin Wire Color Circuit No. Function 1 GY 731 Evaporator Temperature Sensor Signal 2 YE 61 Low Reference

HVAC Control Module Connector Part Information 12110115 32-Way F Micro-Pack 100 Series (BU) Pin Wire Color Circuit No. Function E1 RD/WH 340 Battery Positive Voltage E2 - - Not Used E3 D-BU 1199 Driver Air Temperature Door Control B E4 WH/BK 1236 Passenger Air Temperature Door Control B E5 YE 1318 Mode Door Control B E6 PU 1838 Recirculation Door Control A E7 BN 247 Blower Motor Relay Control E8 GY/BK 754 Blower Motor Speed Control E9 PU 1807 Class 2 Serial Data E10 PU 1807 Class 2 Serial Data E11 L-GN 1478 Coolant Level Switch Signal E12 YE/BK 1814 Mode Door Position Signal E13 L-GN/BK 735 Ambient Air Temperature Sensor Signal E14 D-GN 734 Inside Air Temperature Sensor Signal E15 GY 705 5-Volt Reference E16 - - Not Used F1 BN 141 Ignition 3 Voltage F2 - - Not Used F3 YE 1791 Driver Air Temperature Door Control A F4 GY/BK 2778 Passenger Air Temperature Door Control A F5 TN 2273 Mode Door Control A F6 D-GN 1614 Recirculation Door Control B F7 GY 5127 Afterboil Coolant Pump Supply Voltage (V92) F8 BK/WH 451 Ground F9 D-BU 1646 Passenger Air Temperature Door Position Signal F10 L-BU 733 Driver Air Temperature Door Position Signal F11 GY 1548 Passenger Sunload Sensor Signal F12 L-BU/BK 590 Driver Sunload Sensor Signal F13 WH 278 Ambient Light Sensor Signal F14 GY 731 Evaporator Temperature Sensor Signal F15 YE 61 Low Reference F16 - - Not Used

Inside Air Temperature Sensor Connector Part Information 7283-1020 2-Way F Yazaki 2.3 Series (WH) Pin Wire Color Circuit No. Function 1 D-GN 734 Inside Air Temperature Sensor Signal 2 YE 61 Low Reference

Mode Actuator Connector Part Information IL-AG5-7S-S3C1 7-Way F Molex (L-GN) Pin Wire Color Circuit No. Function 1 YE 61 Low Reference 2 - - Not Used 3 GY 705 5-Volt Reference 4 - - Not Used 5 GY 1814 Mode Door Position Signal 6 PK 1318 Mode Door Control B 7 L-BU 2273 Mode Door Control A

Recirculation Actuator Connector Part Information IL-AG5-7S-S3C1 7-Way F (GN) Pin Wire Color Circuit No. Function 1 D-GN 1614 Recirculation Door Control B 2 - - Not Used 3 PU 1838 Recirculation Door Control A 4-6 - - Not Used 7 BN 41 Ignition 3 Voltage

Sunload/Ambient Light Sensor Connector Part Information 12064760 4-Way F (BK) Pin Wire Color Circuit No. Function A L-BU/BK 590 Driver Sunload Sensor Signal B GY 1548 Passenger Sunload Sensor Signal C YE 61 Low Reference D WH 278 Ambient Light Sensor Signal

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Scan Tool Output Controls

HVAC Control Module Scan Tool Output Controls

ECM Scan Tool Output Controls

Scan Tool Data List

HVAC Control Module Scan Tool Data List

ECM Scan Tool Data List

Circuit Description

The HVAC door actuator is an electronic motor with a feedback potentiometer. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuit. When the actuator reaches the desired position, voltage is removed from the control circuit. The HVAC control module determines the current position of the actuator by monitoring the feedback voltage of the door position signal circuit. The feedback potentiometer position is a function of the actuator position.

1. Air flow position command circuit range refers to the mode actuator
2. Temperature control 1 circuit range refers to the driver air temperature actuator
3. Temperature control 2 circuit range refers to the passenger air temperature actuator

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC B0126 Air Flow Position Command Circuit Range
2. DTC B0409 Temperature Control 1 Circuit Range
3. DTC B0419 Temperature Control 2 Circuit Range

Conditions for Running the DTC

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

Conditions for Setting the DTC

The actual door position differs from the commanded door position by 4 counts or greater for more than 16 seconds.

Action Taken When the DTC Sets

The HVAC control module will not command actuator movement past the point where the stall condition is detected and will continue to make use of the remaining nonrestricted range.

Conditions for Clearing the DTC

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

Test Description

The number below refers to the step number on the diagnostic table.

1. 4: This step verifies that the HVAC control module is able to command the appropriate HVAC actuator.

DTC B0126, B0409, or B0419

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The module supplies a 5-volt source voltage to the potentiometer on the 5-volt reference circuit. The module supplies ground to the potentiometer through the low reference circuit. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes.

1. Air flow position feedback circuit refers to the mode actuator.
2. Temperature control 1 feedback circuit refers to the driver air temperature actuator.
3. Temperature control 2 feedback circuit refers to the passenger air temperature actuator.

This diagnostic procedure supports the following DTCs

1. DTC B0130 Air Flow Position Command Circuit Range
2. DTC B0414 Temperature Control 1 Feedback Circuit
3. DTC B0424 Temperature Control 2 Feedback Circuit

The ignition is turned ON.

The HVAC control module detects the door position signal circuit is less than 7 counts or greater than 250 counts for 1 minute.

The HVAC control module uses only the minimum and maximum door positions.

1. The DTC becomes history when the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 50 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

The number below refers to the step number on the diagnostic table.

1. 4: This step verifies that the HVAC control module is able to command the appropriate HVAC actuator.

DTC B0130, B0414, or B0424

The ambient air temperature (AAT) sensor provides the HVAC control module software with the temperature of the air outside the vehicle. That temperature can be displayed in the driver information center (DIC). A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device, which is proportional to the temperature. As the air temperature increases, the resistance decreases, and the voltage signal decreases. As the air temperature decreases, the resistance increases, and the voltage signal increases.

This diagnostic procedure supports the following DTCs

1. DTC B0160 Outside Air Temperature Sensor Circuit Low
2. DTC B0162 Outside Air Temperature Sensor Circuit Open or High

The ignition is turned ON.

B0160

The HVAC control module detects the AAT sensor signal circuit is less than 2 counts for more than 30 seconds.

B0162

The HVAC control module detects the AAT sensor signal circuit is more than 253 counts for more than 30 seconds.

The DIC will display 15°C (59°F) for outside air temperature.

The system operates using a default value of 15°C.

The system operates using a default value of 15°C.

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

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

1. 3: This step tests for the proper operation of the circuit in the high voltage range.
2. 4: This step 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 B0160 or B0162

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

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B0164 Passenger Compartment Temperature Sensor Circuit Performance

The ignition is turned ON.

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

1. If the DTC sets due to the low condition, the HVAC control module will use ambient temperature value as default in-car value.
2. If the DTC sets due to the high condition, the HVAC control module will use ambient temperature value as default in-car value.

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.

Diagnostic Aids

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

DTC B0164

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The 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.

1. Sunload sensor 1 refers to the left sunload sensor.
2. Sunload sensor 2 refers to the right sunload sensor.

This diagnostic procedure supports the following DTCs

1. DTC B0184 Sunload Sensor 1 Circuit Performance
2. DTC B0189 Sunload Sensor 2 Circuit Performance

The ignition is turned ON.

The HVAC control module detects the signal circuit is less than 0.09 volt (5 counts) or more than 4.9 volts (250 counts).

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

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

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

1. 3: This step tests for the proper operation of the circuit in the high voltage range.
2. 4: This step 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 B0184 or B0189

The engine control module (ECM) monitors the high side refrigerant pressure via the A/C refrigerant pressure sensor. The ECM 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 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 commands the cooling fans on. When pressure is too high or too low the ECM will not allow the A/C compressor clutch to engage. When the DTC is set, the ECM 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 P0531 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.

P0531

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 stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The ECM disables the A/C compressor clutch.
4. The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
5. The ECM 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 .

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

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

DTC P0531, P0532, or P0533

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

The ECM will monitor the control circuit for the following conditions

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 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 driver transitions from ON to OFF or from OFF to ON.

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

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

If DTC P0645, P0646, and 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 ECM is providing ground to the A/C compressor clutch relay. If the light is always ON, the circuit is shorted to ground.
4. 8: This step tests for a short to voltage or an open.
5. 10: If the A/C fuse is open, ensure to test the A/C compressor clutch supply voltage circuit for short to ground.

DTC P0645, P0646, or P0647

The HVAC control module monitors the evaporator temperature via the evaporator temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low.

This diagnostic procedure supports the following DTC

DTC P1531 Air Conditioning (A/C) Evaporator Temperature Sensor Circuit

The ignition is turned ON.

The HVAC control module detects the evaporator temperature sensor signal circuit is less than 0.09 volt (5 counts) or greater than 4.9 volts (250 counts).

1. The driver information center (DIC) will display SERVICE A/C SYSTEM.
2. The A/C OFF segment will illuminate on the HVAC control module.
3. The A/C compressor will be disabled.

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.

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 high voltage range.
2. 4: This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens upon performing this test, the signal circuit has a short to voltage.

DTC P1531

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/i-2003-2009/remont/oem-general-information/#vehicle-dtc-information) 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 the following information: «Air Delivery Description and Operation»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__air-delivery-description-and-operation) «Air Temperature Description and Operation»(/cadillac/srx/i-2003-2009/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»(/cadillac/srx/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__checking-aftermarket-accessories) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(/cadillac/srx/i-2003-2009/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 .

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»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__hvac-compressor-clutch-does-not-engage)
2. «HVAC Compressor Clutch Does Not Disengage»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__hvac-compressor-clutch-does-not-disengage)
3. «Blower Motor Always On»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__blower-motor-always-on)
4. «Blower Motor Inoperative»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__blower-motor-inoperative)
5. «Blower Motor Malfunction»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__blower-motor-malfunction)
6. «Too Hot in Vehicle»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic)
7. «Too Cold in Vehicle»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic__too-cold-in-vehicle)
8. «Air Delivery Improper»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic)
9. «Air Recirculation Malfunction»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic)
10. «Leak Testing»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__leak-testing)
11. «Noise Diagnosis - Blower Motor»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-blower-motor)
12. «Noise Diagnosis - Air Conditioning (A/C) System»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__noise-diagnosis-air-conditioning-ac)
13. «Odor Diagnosis»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__odor-diagnosis)
14. «Steering Wheel Controls Inoperative»(/cadillac/srx/i-2003-2009/remont/ignition-switchsteering-lock/#steering-wheel-and-steering-column)

HVAC Compressor Clutch Does Not Engage

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

Blower Motor Malfunction

Blower Motor Malfunction

Blower Motor Always On - Auxiliary

Blower Motor Always On - Auxiliary

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

1. 2: This step tests to verify that the auxiliary blower motor operates.
2. 3: This step determines if the malfunction is on the supply voltage side of the auxiliary blower motor.
3. 4: This step determines if the malfunction is the auxiliary blower motor or on the grounding side of the auxiliary blower motor.

Blower Motor Inoperative - Auxiliary

Blower Motor Malfunction - Auxiliary

Blower Motor Malfunction - Auxiliary

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

1. 6: The ambient air temperature must be above 3°C (38°F) for this A/C compressor test.
2. 7: The specified values are from the A/C System Performance Test.

Too Hot in Vehicle

Too Cold in Vehicle

Too Cold in Vehicle

1. The condition may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__testing-for-intermittent-conditions-and-poor) in Wiring Systems.
2. Inspect the air delivery system for the following conditions: A dirty HVAC air filter An obstruction to the airflow Air leaks Misaligned air ducts Broken or binding linkages or doors

Air Delivery Improper

1. If the control A circuit of the recirculation actuator is shorted to ground, the following conditions will occur. The recirculation actuator will operate properly when recirculation is requested. The recirculation actuator will continually modulate between the outside air and recirculation positions when outside air is requested.
2. If the control B circuit of the recirculation actuator is shorted to ground, the following conditions will occur. The recirculation actuator will operate properly when outside air is requested. The recirculation actuator will continually modulate between the outside air and recirculation positions when recirculation is requested.
3. The condition may be intermittent - Refer to «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/i-2003-2009/remont/body-electrical/#how-to-diagnosis-repair-the-wiring-systems-testing__testing-for-intermittent-conditions-and-poor) in Wiring Systems.
4. Inspect the recirculation door and the recirculation actuator for the following conditions: A misaligned recirculation actuator - Refer to «Recirculation Actuator Replacement»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#hvac-systems-automatic) . Broken or binding linkages A broken or binding recirculation door An obstruction that prevents the recirculation door from operating within its full range of motion Missing seals to the recirculation door Misaligned seals to the recirculation door

Air Recirculation Malfunction

Afterblow Enable Procedure

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 reprogramming the HVAC control module, refer to Service Programming System (SPS) in Vehicle Control Systems.

After the HVAC control module has been programmed for afterblow, the following conditions must be met for afterblow to operate

1. The engine has been turned off for at least 30 minutes.
2. The ambient air temperature is at least 21°C (70°F).
3. The A/C compressor operated for more than 2 minutes.
4. The system voltage is at least 12 volts.

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

1. The blower motor will run for 20 seconds.
2. The blower motor will be off for 10 minutes.
3. The blower motor will run for and additional 20 seconds.

Removal Procedure

1. Turn the engine OFF.
2. Apply parking brake and place the transmission into the lowest gear setting.
3. Remove the screw behind the ashtray.
4. Remove the HVAC control module trim plate by pulling outward on right and left side.
5. Disconnect the HVAC control module electrical connector.
6. Disconnect the ash tray electrical connector.
7. Remove the HVAC control module screws (1).
8. Remove the HVAC control module.

Installation Procedure

1. Install the HVAC control module into the trim plate.
2. Install the HVAC control module screws (1). Tighten: Tighten the screws to 2 N.m (18 lb in).
3. Connect the HVAC control module electrical connector.
4. Connect the ash tray electrical connector.
5. Install the HVAC control module trim plate by pressing trim until tabs engage.
6. Install the screw behind the ashtray. Tighten: Tighten the screw to 2 N.m (18 lb in).
7. Place the transmission in park and unapply the parking brake.

1. Remove the right sound insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.
2. Disconnect the electrical connector from the blower motor control processor.
3. Remove the blower motor control processor retaining screw.
4. Remove the blower motor control processor from the vehicle.

1. Install the blower motor control processor.
2. Install the blower motor control processor retaining screw. Tighten: Tighten the screw to 1 N.m (9 lb in).
3. Connect the electrical connector to the blower motor control processor.
4. Install the right sound insulator. Refer to «Closeout/Insulator Panel Replacement - Right»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.

1. Remove the air inlet assembly. Refer to «Air Inlet Assembly Replacement»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning) in Heating, Ventilation and Air Conditioning.
2. Disconnect the electrical connector from the recirculation actuator.
3. Remove the recirculation actuator screws.
4. Remove the recirculation actuator.

1. Install the recirculation actuator.
2. Install the recirculation actuator screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
3. Connect the electrical connector to the recirculation actuator.
4. Install the air inlet assembly. Refer to «Air Inlet Assembly Replacement»(/cadillac/srx/i-2003-2009/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning) in Heating, Ventilation and Air Conditioning.

1. Remove the instrument panel (I/P) carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Disconnect the mode actuator electrical connector.
3. Remove the mode actuator screws.
4. Remove the mode actuator.

1. If replacing the mode actuator, transfer the lever from the old actuator to the new actuator.
2. Install the mode actuator.
3. Install the mode actuator screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
4. Connect the electrical connector to the actuator.
5. Install the I/P carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.

1. Remove the right closeout panel. Refer to «Closeout/Insulator Panel Replacement - Right»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the instrument panel compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
3. Disconnect the right air temperature actuator electrical connector.
4. Remove the right air temperature actuator screws.
5. Remove the right air temperature actuator.

1. Install the right air temperature actuator.
2. Install the right air temperature actuator screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
3. Connect the right air temperature actuator electrical connector.
4. Install the instrument panel compartment. Refer to «Compartment Replacement - Instrument Panel (I/P)»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
5. Install the right closeout panel. Refer to «Closeout/Insulator Panel Replacement - Right»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.

1. Remove the instrument panel (I/P) carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the left air temperature actuator screws.
3. Remove the left air temperature actuator harness screw.
4. Disconnect the left air temperature actuator electrical connector from the actuator.
5. Remove the left air temperature actuator.

1. Install the left air temperature actuator.
2. Install the left air temperature actuator harness screw. Tighten: Tighten the screws to 1 N.m (9 lb in).
3. Connect the left air temperature actuator electrical connector to the actuator.
4. Install the left air temperature actuator screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
5. Install the instrument panel (I/P) carrier. Refer to «Instrument Panel (I/P) Carrier Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.

1. Remove the knee bolster. Refer to «Knee Bolster Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.
2. Disconnect the aspirator hose from the HVAC module.
3. Remove the inside air temperature sensor (2) from the instrument panel (I/P) by gently prying outward.
4. Disconnect the aspirator hose (3) from the inside air temperature sensor.
5. Remove the aspirator hose.

1. Install the aspirator hose.
2. Connect the aspirator hose (3) to the inside air temperature sensor.
3. Install the inside air temperature sensor (2) to the I/P.
4. Connect the aspirator hose to the HVAC module.
5. Install the knee bolster. Refer to «Knee Bolster Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages, and Console.

1. Disconnect the ambient air temperature sensor electrical connector (1).
2. Release the ambient air temperature sensor from the clip.
3. Remove the ambient air temperature sensor from the vehicle.

1. Place the ambient air temperature sensor in position.
2. Engage the ambient air temperature sensor into the clip.
3. Connect the ambient air temperature electrical connector (1).

1. Remove the knee bolster. Refer to «Knee Bolster Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Disconnect the aspirator hose from the HVAC module.
3. Remove the inside air temperature sensor (2) from the I/P by gently prying outward.
4. Disconnect the inside air temperature sensor (2) electrical connection (1).
5. Disconnect the aspirator hose (3) from the inside temperature sensor (2).
6. Remove the inside air temperature sensor (2).

1. Install the inside air temperature sensor (2).
2. Connect the aspirator hose (3) to the inside temperature sensor (2).
3. Connect the inside air temperature sensor electrical connector (1).
4. Install the inside air temperature sensor (2) into the I/P.
5. Connect the aspirator hose to the HVAC module.
6. Install the knee bolster. Refer to «Knee Bolster Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.

1. Remove the defroster grille. Refer to «Defroster Grille Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.
2. Remove the sunload sensor from the defroster grille by twisting the sensor 1/4 turn counter clockwise.
3. Disconnect the sunload sensor electrical connector.
4. Remove the sunload sensor.

1. Connect the sunload sensor electrical connector.
2. Install the sunload sensor to the defroster grille by twisting the sensor 1/4 turn clockwise.
3. Install the defroster grille. Refer to «Defroster Grille Replacement»(/cadillac/srx/i-2003-2009/remont/gauges-instrument-panels/#instrument-panel-gages-and-console) in Instrument Panel, Gages and Console.

1. Remove the overhead console (1).
2. Disconnect the blower motor switch electrical connector.
3. Remove the blower motor switch screws.
4. Remove the blower motor switch from the dome lamp housing.

1. Install the blower motor switch to the dome lamp housing.
2. Install the blower motor switch screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
3. Connect the blower motor switch electrical connector.
4. Install the overhead console (1).

1. Remove the center dome lamp assembly.
2. Disconnect the auxiliary blower motor switch (1) electrical connector.
3. Remove the auxiliary blower motor switch (1) screws.
4. Remove the auxiliary blower motor switch (1) from the dome lamp housing.

1. Install the auxiliary blower motor switch (1) to the dome lamp housing.
2. Install the auxiliary blower motor switch (1) screws. Tighten: Tighten the screws to 1 N.m (9 lb in).
3. Connect the auxiliary blower motor switch (1) electrical connector.
4. Install the center dome lamp assembly.

Air Delivery Description and Operation

The Air Delivery Description and Operation is divided into 5 primary areas

1. HVAC Control Components
2. Air Speed
3. Air Speed Auxiliary
4. Air Distribution
5. Recirculation
6. 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). The dash integration module (DIM), which is the vehicle power mode master, provides a device on signal. The control module supports the following features

Air Delivery Description and Operation

The HVAC control module will receive information that defines the current driver of the vehicle from the driver door module (DDM) through class 2 communication. The HVAC system will memorize the following system configurations for up to 2 unique drivers

1. Driver set temperature
2. Passenger set temperature
3. Mode
4. Blower motor speed
5. A/C compressor request, auto ON or A/C OFF

This information shall be stored inside the HVAC control module memory. When a different driver identification button is selected the HVAC control module will recall the appropriate driver settings. When the HVAC control module is first turned on, the last stored settings for the current driver will be activated except for the rear defrost and heated seat settings.

Mode Actuator

The mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 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 one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Recirculation Actuator

The recirculation actuator is a 3-wire uni-directional electric motor. Ignition 3 voltage and two control circuits enable the actuator to operate. The control circuits are either grounded or opened during normal operation. In order to move the actuator, the HVAC control module grounds one of the control circuits.

Blower Motor Relay

The blower motor relay provides a supply voltage to the blower motor and blower motor control processor. The HVAC control module commands the blower motor relay ON anytime the commanded blower speed is not OFF.

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 supply 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 control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

Air Speed

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position 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.

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 reprogramming the HVAC control module, refer to Service Programming System (SPS) in Programming.

After the HVAC control module has been programmed for afterblow, the following conditions must be met for afterblow to operate

1. The engine has been turned off for at least 30 minutes.
2. The ambient air temperature is at least 21°C (70°F).
3. The A/C compressor operated for more than 2 minutes before shut down.
4. The system voltage is at least 12 volts.

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

1. The blower motor will RUN for 20 seconds.
2. The blower motor will be OFF for 10 minutes.
3. The blower motor will RUN for and additional 20 seconds.

Auxiliary Air Speed

Auxiliary A/C has a blower motor that is independent to that system. Voltage is supplied to the auxiliary blower motor from the rear fuse block. The auxiliary A/C blower motor switch applies ground to the auxiliary blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the auxiliary blower motor per particular speed request

1. Low speed-3 resistors
2. Medium 1 speed-2 resistors
3. Medium 2 speed-1 resistor

When the operator requests High speed, ground is applied directly to the auxiliary blower motor.

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. In the outside air position, the incoming air is filtered by the passenger compartment air filter.

Recirculation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in defrost. When the mode is in defog, Recirculation will only be available for 10 minutes. In the outside air position, the incoming air is filtered by the passenger compartment air filter.

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 full automatic operation, the AUTO selection must be activated.

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

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

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

When the coldest position is selected in automatic operation the blower will stay on high and the air temperature actuators will stay in the full cold position. The mode actuator will remain in the panel position and the recirculation actuator will remain in the recirculation position.

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

Air Temperature Description and Operation

The air temperature controls are divided into 3 primary areas

1. Automatic Operation
2. The Heating and Air Conditioning System
3. The 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). The dash integration module (DIM), which is the vehicle power mode master, provides a device on signal. The control module supports the following features

Air Temperature Description and Operation

The HVAC control module will receive information that defines the current driver of the vehicle from the driver door module (DDM) through class 2 communication. The HVAC system will memorize the following system configurations for up to 2 unique drivers

1. Driver set temperature
2. Passenger set temperature
3. Mode
4. Blower motor speed
5. A/C compressor request, auto ON or A/C OFF

This information shall be stored inside the HVAC control module memory. When a different driver identification button is selected the HVAC control module will recall the appropriate driver settings. When the HVAC control module is first turned on, the last stored settings for the current driver will be activated except for the rear defrost and heated seat settings.

Air Temperature Actuators

The air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 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 one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Air Temperature Sensors

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

1. Ambient
2. Inside

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

The inside temperature sensor operates within a temperature range between -6.5°C and 57.5°C (20.3-135.5°F). If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. The ambient sensor operates within a temperature range between -30 to 51°C (-22 to 123.8°F). If the HVAC control module has determined that the ambient temperature sensor has failed, the driver information center (DIC) display shall display 59°F in place of the outside air temperature. If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. If the engine coolant temperature is not more than 3°C (5.4°F) above the sensor reading, or if the engine has not been started in 3 hours, then the actual ambient air temperature sensor reading is displayed. Also at vehicle speeds greater than 35 km/h (22 mph), the ambient air temperature displayed may be allowed to increase, but only at a slow, filtered rate. The driver information center (DIC) displays the ambient air temperature value that it receives from the HVAC control module through a class 2 message. The ambient air temperature value can be updated by an outside air instant update feature.

To use this feature, press the following switches on the HVAC control module simultaneously

1. AUTO
2. MODE UP
3. LEFT TEMPERATURE UP

Sunload Sensor

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The 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 sensor is open or shorted, no sunload adjustment occurs and the SERVICE A/C SYSTEM message is displayed.

Evaporator Temperature Sensor

The HVAC control module monitors the temperature of the air passing through the evaporator by the A/C evaporator air temperature sensor. This sensor is located on the evaporator core. The temperature is used to cycle the A/C compressor ON and OFF to prevent the evaporator core from freezing. A thermistor inside the sensor varies its resistance to monitor the evaporator air temperature. The HVAC control module monitors the voltage drop across the thermistor when supplied with a 5-volt reference signal. The HVAC control module will send a class 2 message to the ECM to stop requesting the A/C compressor clutch operation if the temperature drops below 3°C (37°F). The sensor must be above 4°C (39°F) to request the A/C compressor clutch again.

The sensor operates within a temperature range between -40°C to 215°C (-40 to 355°F). If the HVAC control module detects an open in the evaporator temperature sensor or circuit, the class 2 message sent to the ECM will not submit the A/C ON request. The HVAC control module will then send a request to the Radio for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The HVAC control module will also display A/C OFF on the module as long as the condition is present.

A/C Refrigerant Pressure Sensor

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

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

If the ECM detects a failure in the A/C refrigerant pressure sensor or circuit, the class 2 message sent to the HVAC control module will be invalid. The HVAC control module will then send a request to the radio for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The HVAC control module will also display A/C OFF on the module as long as the condition is present.

Heating and A/C Operation

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

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

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

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

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

1. WARMEST POSITION - The air temperature actuator door position directs maximum air flow through the heater core.
2. COLDEST POSITION - The air temperature actuator door position directs maximum air flow around the heater core.

BETWEEN THE WARMEST AND COLDEST POSITION - The following sensors are monitored to direct the appropriate amount of air through the heater core to achieve the desired temperature

1. Sunload
2. Ambient temperature
3. Inside temperature

The A/C system is engaged by selecting any switch on the HVAC control module except the A/C OFF switch. The A/C switch will illuminate A/C OFF when the A/C switch is selected. The control module sends a class 2 A/C request message to the engine control module (ECM) for A/C compressor clutch operation. The following conditions must be met in order for the ECM to turn on the compressor clutch

1. HVAC control module Evaporator Temperature more than 4°C (39°F) Control module operating range 9 and 16 volts
2. ECM Engine coolant temperature (ECT) is less than 125°C (257°F) or 120°C (248°F) for PV8 Engine RPM is between 0 RPM and 6000 RPM A/C pressure is between 3137 kPa (455 psi) or 2850 kPa (413 psi) for PV8 and 193 kPa (28 psi) or 200 kPa (29 psi) for PV8.

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

1. Throttle position is 100 percent.
2. A/C pressure is more than 3137 kPa (455 psi) or 2850 kPa (413 psi) for PV8.
3. A/C pressure is less than 193 kPa (28 psi) or 200 kPa (29 psi) for PV8.
4. Engine coolant temperature (ECT) is more than 125°C (257°F) or 120°C (248°F) for PV8.
5. Engine speed is more than 5,500 RPM.
6. Transmission shift
7. ECM detects excessive torque load.
8. ECM detects insufficient idle quality.
9. ECM detects a hard launch condition.

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

Dual Zone Operation

The HVAC control module has temperature settings for the driver and the passenger. If the passengers setting is turned off then the drivers setting controls both driver and passenger temperature actuators. The passengers setting can not be used without the drivers setting also being ON. The passengers setting can be turned ON or OFF by pressing the power button in the center of the passengers temperature rocker switch. When the passengers setting is ON, the passenger temperature can be adjusted independently from the drivers setting and the passenger temperature is displayed on the passengers side of the control module. A different sunload on one side of the vehicle may cause different discharge air temperatures even when the passengers setting is not turned ON.

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

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

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

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

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

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

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

A/C Cycle

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

The Denso 10S20 fixed displacement swash plate A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the discharge hose, and forced to flow to the condenser and then through the balance of the A/C system. The A/C system is mechanically protected with the use of a high pressure relief valve. If the high pressure switch were to fail or if the refrigerant system becomes restricted and refrigerant pressure continued to rise, the high pressure relief will pop open and release refrigerant from the system.

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

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

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

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

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

Special Tools

Special Tools Illustration Tool Number/ Description 7000081 TECH 2 Diagnostic Scan Tool

Scheme 25

See also:
• Diagnostic System Check - Vehicle
• Circuit Testing
• Wiring Repairs
• Testing for Intermittent Conditions and Poor Connections
• Connector Repairs
• Control Module References
• Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
• Checking Aftermarket Accessories
• Leak Testing
• Noise Diagnosis - Blower Motor
• Noise Diagnosis - Air Conditioning (A/C) System
• Odor Diagnosis
• Steering Wheel Controls Inoperative
• Compressor Replacement (LH2 - Heavy Duty Cooling)
• After Boil Coolant Pump Inoperative
• Heating Performance Diagnostic
• Service Programming System (SPS)
• Fastener Notice
• Closeout/Insulator Panel Replacement - Right
• DTC B0126, B0409, or B0419
• HVAC Connector End Views
• Air Delivery Description and Operation
• Air Temperature Description and Operation
• HVAC Compressor Clutch Does Not Engage
• HVAC Compressor Clutch Does Not Disengage
• Blower Motor Always On
• Blower Motor Inoperative
• Blower Motor Malfunction
• Too Cold in Vehicle
• Sensor Resistance Table