HVAC System - Manual Buick Regal V

Scheme 1

Scheme 2

Scheme 3

HVAC Component Replacement Reference

HVAC COMPONENT REPLACEMENT REFERENCE

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptors

DTC B0193 01: Front Blower Motor Speed Circuit Short to Battery

DTC B0193 06: Front Blower Motor Speed Circuit Low Voltage/Open

Diagnostic Fault Information

Circuit/System Description

The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor speed control from the HVAC control module, battery positive and ground circuits enable the blower motor control module to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the blower motor control module in order to command the blower motor speed. The blower motor control module transfers the PWM signal into a corresponding blower motor voltage.

Conditions for Running the DTC

1. Ignition ON
2. The HVAC control module is ON

Conditions for Setting the DTC

B0193 01 The voltage at the HVAC control module output to the blower motor control module is always high.

B0193 06 The voltage at the HVAC control module output to the blower motor control module is always low or fluctuating.

Action Taken When the DTC Sets

The blower motor is inoperative

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present

Diagnostic Aids

Prior to motor replacement connect a direct independent B+ and ground to verify operation

Inspect the motor shaft for rust or other foreign material which may prohibit proper motor operation

If the motor operates properly please reinstall it, check for PIs or TSBs, and refer to TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS .

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS -- INDEX

Description and Operation

Manual HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Circuit/System Testing

1. Ignition OFF and all vehicle systems off, disconnect the X1 harness connector at the K8 blower motor control module. It may take up to 2 minutes for all vehicle systems to power down
2. Test for less than 10ohms between the ground circuit terminal 5 and ground. If 10ohms or greater Ignition OFF Test for less than 2ohms in the ground circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, repair the open/high resistance in the ground connection If less than 10ohms
3. Ignition ON
4. Verify a test lamp illuminates between the B+ circuit terminal 6 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF Test for less than 2ohms in the B+ circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, verify the fuse is not open and there is voltage at the fuse If the test lamp does not illuminate and the circuit fuse is open 1 Ignition OFF 2 Test for infinite resistance between the B+ circuit terminal 6 and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K8 blower motor control module
5. Connect a DMM between the control circuit terminal 3 and ground
6. Verify the resistance value is between 500ohms and 230Kohms and there is a noticeable change with each change in commanded fan speed If not within the specified range or there is no noticeable change Ignition OFF, disconnect the X2 harness connector at the K33 HVAC control module Test for less than 1 V between the control circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms replace the K33 HVAC control module If within the specified range and there is a noticeable change
7. Ignition OFF, connect the X1 harness connector at the K8 blower motor control module, and disconnect the harness connector at the M8 blower motor, ignition ON and blower ON
8. Verify a test lamp illuminates between the control circuit terminal B and ground If the test lamp does not illuminate Ignition OFF, disconnect the X2 harness connector at the K8 blower motor control module Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms replace the K8 blower motor control module
9. Connect a test lamp between control circuit terminal A and control circuit terminal B
10. Verify the test lamp becomes progressively brighter as the blower speed is increased and progressively dimmer as the blower speed is decreased If the test lamp does not illuminate Ignition OFF, disconnect the X2 harness connector at the K8 blower motor control module Test for less than 1 V between the control circuit terminal A and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms replace the K8 blower motor control module If the test lamp illuminates, but does not change in brightness 1 Ignition OFF, disconnect the X2 harness connector at the K8 blower motor control module 2 Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K8 blower motor control module If the test lamp changes in brightness as the blower speed is changed
11. Test or replace the M8 blower motor

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC B0223 01: Recirculate Position Command 1 Circuit Short to Battery

DTC B0223 06: Recirculate Position Command 1 Circuit Low Voltage/Open

DTC B0233 01: Air Flow Control Circuit Short to Battery

DTC B0233 06: Air Flow Control Circuit Low Voltage/Open

DTC B023A 02: HVAC Actuators Supply Voltage Short to Ground

DTC B0408 01: Main Temperature Control Circuit Short to Battery

DTC B0408 06: Main Temperature Control Circuit Low Voltage/Open

Stepper motors are used for temperature regulation, air distribution control and recirculation door control

With the switches on the Radio/HVAC control, air temperature door position, mode door position and recirculation door position can be selected. The selected values are passed to the HVAC control module via the serial data. The HVAC control module supplies a 12 V reference voltage to the stepper motors and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motors move the appropriate doors into the calculated positions, in order to reach the desired positions

1. Ignition ON
2. The HVAC control module is ON

B023A 02 The stepper motors supply output is shorted to ground

B0223 01, B0233 01, B023A 01, or B0408 01 At least one control circuits of the appropriate stepper motor is shorted to voltage when motor starts moving. Faults are not detected when motor is already running or target position is already reached

B0223 06, B0233 06, B0233 06, or B0408 06 At least one control circuits of the appropriate stepper motor is shorted to ground or open when motor starts moving. Faults are not detected when motor is already running or target position is already reached

B023A 02

1. The affected output will be switched off for hardware protection
2. All stepper motors are deactivated

B0223, B0233, B023A, or B0408

1. * The affected output will be switched off for hardware protection
2. The affected stepper motor is deactivated

The condition for setting the DTC is no longer present

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Note. This diagnosis requires the use of a GM approved test lamp (J-35616-210) or equivalent. Failure to do so may result in misdiagnosis of the module

1. Ignition OFF, disconnect the harness connector at the appropriate door actuator, ignition ON
2. Connect a test lamp between the control circuit terminal 2 and ground
3. Verify the test lamp is blinking after commanding the appropriate door actuator in both directions with a scan tool If the test lamp is always OFF Ignition OFF, disconnect the harness connector at the K33 HVAC control module Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module If the test lamp is always ON 1 Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON 2 Test for less than 1 V between the control circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V, replace the K33 HVAC control module
4. Connect a test lamp between each actuator harness connector control terminal listed below and B+. Control Circuit - terminal 1 Control Circuit - terminal 3 Control Circuit - terminal 4 Control Circuit - terminal 6
5. Verify the test lamp is blinking after commanding the appropriate door actuator in both directions with a scan tool If the test lamp is always OFF Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON Test for less than 1 V between the control circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Ignition OFF Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module If the test lamp is always ON 1 Ignition OFF, disconnect the harness connector at the K33 HVAC control module 2 Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K33 HVAC control module
6. Replace the actuator

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC B3933 02: Air Conditioning Evaporator Temperature Sensor Circuit Short to Ground

DTC B3933 05: Air Conditioning Evaporator Temperature Sensor Circuit High Voltage/Open

The evaporator air temperature sensor is 2-wire negative temperature co-efficient thermistor

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 voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +85°C (-40 to +185°F). The sensor signal varies between 0-5 V. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease. If the HVAC control module detects a malfunctioning sensor, then the control module software will use a default air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected

1. Ignition ON
2. The HVAC control module is ON

The HVAC control module detects the sensor signal out of range. The signal voltage is less than 0.1 V or greater than 4.9 V for more than 50 ms

The system operates using a default value.

The sensor signal is within specified range between 0.1-4.9 V

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B39 Evaporator Temperature Sensor. It may take up to 2 minutes for all vehicle systems to power down
2. Test for less than 10ohms between the low reference circuit terminal B and ground If 10ohms or greater Ignition OFF, disconnect the harness connector at the K33 HVAC control module Test for less than 2ohms in the low reference circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module
3. Ignition ON
4. Verify the A/C Evaporator Temperature Sensor scan tool parameter is less than -37°C (-35°F). If -37°C (-35°F) or greater Ignition OFF, disconnect the harness connector at the K33 HVAC control module Test for infinite resistance between the signal circuit terminal A and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K33 HVAC control module
5. Install a 3 A fused jumper wire between the signal circuit and the low reference circuit terminal B
6. Verify the A/C Evaporator Temperature Sensor scan tool parameter is greater than 115°C (239°F). If 115°C (239°F) or less Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON Test for less than 1 V between the signal circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Ignition OFF Test for less than 2ohms in the signal circuit end to end. If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module
7. Test or replace the B39 Evaporator Temperature Sensor

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC B393B 04: Air Conditioning Compressor Valve Control Circuit Open

DTC B393B 0B: Air Conditioning Compressor Valve Control Circuit High Current

This A/C system uses a conventional clutch to engage and mechanically turn the compressor, and a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a (PWM) signal in order to determine the amount of compressor displacement. The performance of the A/C compressor is based on adjusted interior temperature and engine load.

1. Ignition ON
2. The HVAC control module is ON

B393B 04 A PWM greater than 10% is sent but no current is read back

B393B 0B Measured current is above threshold of 815 mA

B393B 04 The A/C compressor is disabled

B393B 0B

1. The A/C compressor is disabled
2. Output will be switched off for hardware protection

The condition for setting the DTC is no longer present

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q46 A/C compressor solenoid valve. It may take up to 2 minutes for all vehicle systems to power down
2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground If the test lamp does not illuminate Test for infinite resistance between the B+ circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2ohms in the B+ circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module If the test lamp illuminates
3. Ignition ON, connect a test lamp between the control circuit terminal 1 and the B+ circuit terminal 2
4. Verify the test lamp turns ON and OFF when commanding the A/C Compressor Refrigerant Solenoid Valve ON and OFF with a scan tool If the test lamp is always OFF Ignition OFF, disconnect the harness connector at the K33 HVAC control module, ignition ON Test for less than 1 V between the control circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Ignition OFF Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K33 HVAC control module. If the test lamp is always ON 1 Ignition OFF, disconnect the harness connector at the K33 HVAC control module 2 Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K33 HVAC control module If the test lamp is always OFF
5. Test or replace the Q46 A/C compressor solenoid valve

Component Testing

1. Ignition OFF, disconnect the harness connector at the Q46 Air Conditioning Compressor Valve
2. Test for 7-15ohms between B+ circuit terminal 2 and control circuit terminal 1
3. Test for infinite resistance between each terminal and the Q46 Air Conditioning Compressor Valve housing/case
4. All OK

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC P0532 : Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage

DTC P0533 : Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM supplies a 5 V reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the 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

1. Engine is running
2. Any of the conditions for setting the DTC are met for 15 seconds
3. Battery voltage is between 11-18 V

1. The ECM detects that the A/C pressure is less than 1 psi (0.01 V).
2. The ECM detects that the A/C pressure is more than 428 psi (4.92 V).

This is a type D DTC

This is a type D DTC

A malfunction within the refrigerant system causing high pressure can cause this DTC to set

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Circuit System Verification

1. Ignition ON
2. Verify the scan tool engine control module A/C High Side Pressure Sensor parameter is between 6.8 kPa (1 psi) and 2950 kPa (428 psi).
3. All OK

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B1 A/C refrigerant pressure sensor. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 10ohms between the low reference circuit terminal 1 and ground If 10ohms or greater Ignition OFF, disconnect the X1 harness connector at the K20 engine control module Test for less than 2ohms in the low reference circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K20 engine control module
3. Ignition ON
4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground If less than 4.8 V Ignition OFF, disconnect the X1 harness connector at the K20 engine control module Test for infinite resistance between the 5 V reference circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2ohms in the 5 V reference circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K20 engine control module
5. Verify the scan tool engine control module A/C High Side Pressure Sensor parameter is less than .25 V If .25 V or greater Ignition OFF, disconnect the X1 harness connector at the K20 engine control module, ignition ON Test for less than 1 V between the signal circuit terminal 3 and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V, replace the K20 engine control module
6. 6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 2
7. Verify the scan tool engine control module A/C High Side Pressure Sensor parameter is greater than 4.8 V If 4.8 V or less Ignition OFF, disconnect the X1 harness connector at the K20 engine control module Test for infinite resistance between the signal circuit terminal 3 and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance Test for less than 2 ohms in the signal circuit end to end If 2 ohms or greater, repair the open/high resistance in the circuit If less than 2 ohms, replace the K20 engine control module
8. Test or replace the B1 A/C refrigerant pressure sensor

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

1. Perform the «Diagnostic System Check - Vehicle»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/buick/regal/v-2009-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC P0645 : Air Conditioning (A/C) Compressor Clutch Relay Control Circuit

DTC P0646 : Air Conditioning (A/C) Compressor Clutch Relay Control Circuit Low Voltage

DTC P0647 : Air Conditioning (A/C) Compressor Clutch Relay Control Circuit High Voltage

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via serial data. The ECM then grounds the A/C compressor clutch relay coil control circuit, closing the relay contacts. The closed relay contacts provide voltage to the compressor clutch causing it to engage

1. Engine is running
2. The HVAC control module is ON
3. The A/C switch is active

P0645 or P0646 : The ECM detects a short to ground or an open at the A/C compressor clutch relay control circuit

P0647 : The ECM detects a short to voltage at the A/C compressor clutch relay control circuit

P0645 or P0646 : The A/C compressor is inoperative or always active. The A/C compressor solenoid is commanded to 0% displacement. This causes warm air from the ducts, even with unwanted clutch engagement

P0647 : The A/C compressor is inoperative

The condition for setting the DTC is no longer present

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

1. Ignition OFF, disconnect the KR29 A/C compressor clutch relay, ignition ON.
2. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground If the test lamp does not illuminate and the circuit fuse is good Ignition OFF Test for less than 2ohms in the B+ circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, verify the fuse is not open and there is voltage at the fuse If the test lamp does not illuminate and the circuit fuse is open 1 Ignition OFF 2 Test for infinite resistance between the B+ circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance 3 Disconnect the harness connector at the Q2 A/C compressor clutch 4 Test for infinite resistance between the control circuit terminal 87 and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, test or replace the Q2 A/C compressor clutch
3. Ignition ON
4. Verify a test lamp illuminates between the ignition circuit terminal 86 and ground
5. Connect a test lamp between the ignition circuit terminal 86 and the control circuit terminal 85
6. Verify the test lamp turns ON and OFF when commanding the Engine Control Module A/C Compressor Clutch Relay ON and OFF with a scan tool If the test lamp is always OFF Ignition OFF, disconnect the harness connector at the K20 engine control module, ignition ON Test for less than 1 V between the control circuit and ground If 1 V or greater, repair the short to voltage on the circuit If less than 1 V Ignition OFF Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, replace the K20 engine control module If the test lamp is always ON 1 Ignition OFF, disconnect the harness connector at the K20 engine control module 2 Test for infinite resistance between the control circuit and ground If less than infinite resistance, repair the short to ground on the circuit If infinite resistance, replace the K20 engine control module
7. Verify a test lamp does not illuminate between the control circuit terminal 87 and ground
8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q2 A/C compressor clutch. It may take up to 2 minutes for all vehicle systems to power down
9. Test for less than 10ohms between the ground circuit terminal 1 and ground If 10ohms or greater Ignition OFF Test for less than 2ohms in the ground circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, repair the open/high resistance in the ground connection If less than 10ohms
10. Connect the harness connector at the Q2 A/C compressor clutch
11. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87
12. Verify the Q2 A/C compressor clutch is activated If the Q2 A/C compressor clutch does not activate Ignition OFF, disconnect the harness connector at the Q2 A/C compressor clutch Test for less than 2ohms in the control circuit end to end If 2ohms or greater, repair the open/high resistance in the circuit If less than 2ohms, test or replace the Q2 A/C compressor clutch If the Q2 A/C compressor clutch activates
13. Test or replace the KR29 A/C compressor clutch relay

1. Ignition OFF, disconnect the KR29 A/C compressor clutch relay
2. Test for 60-180ohms between terminals 85 and 86
3. Test for infinite resistance between the terminals listed below: 30 and 86 30 and 87 30 and 85 85 and 87 If less than infinite resistance Replace the KR29 A/C compressor clutch relay If infinite resistance
4. Install a 15 A fused jumper wire between terminal 86 and 12 V. Install a jumper wire between terminal 85 and ground
5. Test for less than 2ohms between terminals 30 and 87
6. All OK

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

Symptoms - HVAC Systems - Manual

Note. The following steps must be completed before using the symptom tables: Perform the Diagnostic System Check - Vehicle before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link. Review the system operation in order to familiarize yourself with the system functions. Refer to Manual HVAC Description and Operation

Visual/Physical Inspection

1. Inspect for aftermarket devices which may affect the operation of the HVAC System. Refer to «CHECKING AFTERMARKET ACCESSORIES»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which may cause the symptom
3. Verify the A/C compressor 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.
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 System Malfunction»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual)

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Check the following mechanical fault sources

1. Air distribution box
2. Air distribution hoses/air distribution ducts

HVAC Schematics

COMPONENT CONNECTOR END VIEWS -- INDEX

Manual HVAC Description and Operation

1. «Circuit Testing»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/buick/regal/v-2009-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Control Module References for scan tool information

Special Tools

J43600 ACR Air Conditioning Service Center

Note. Check for bulletins before proceeding.

1. Ignition ON
2. Verify the scan tool Blower Motor Switch parameter changes when rotating the blower switch through each speed position
3. Verify the blower motor operates properly with the blower motor switch in each speed position
4. Verify the scan tool parameters listed below change when pressing the appropriate switch Left Temperature Knob Position Air Recirculation Mode Switch Bi-Level Switch If any parameter does not change Replace the A26 HVAC controls If all parameters change
5. Verify the HVAC doors listed below move when pressing the appropriate switch Temperature Bi-Level mode Recirculation If any HVAC door does not move Refer to «DTC B0223, B0233, B023A, or B0408»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual) If all HVAC doors move
6. Install the J43600 Air Conditioning Service Center
7. Verify the high side pressure reading on the Air Conditioning Service Center is within 10% of the scan tool A/C High Side Pressure Sensor parameter
8. Verify the A/C High Side Pressure Sensor parameter is between 269-2929 kPa (39-425 PSI).
9. Engine ON, A/C system ON
10. Verify cool air flows from the ducts with the temperature control in the coldest position If the air is not cool Observe the Q2 A/C Compressor Clutch Verify the Q2 A/C Compressor Clutch is engaged If the Q2 A/C Compressor Clutch is not engaged Refer to «DTC P0645, P0646, or P0647»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual) If the Q2 A/C Compressor Clutch is engaged. Refer to «AIR CONDITIONING (A/C) SYSTEM PERFORMANCE TEST»(/buick/regal/v-2009-2013/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__air-conditioning-ac-system-performance-test) and «DTC B393B»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual) If the air is cool
11. Verify warm air flows from the ducts with the temperature control in the warmest position
12. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(/buick/regal/v-2009-2013/remont/manual-hvac-system/#hvac-system-manual__hvac-component-replacement-reference)
2. «Control Module References»(/buick/regal/v-2009-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

Heater and Air Conditioning Control Replacement

Callout Component Name Preliminary Procedures Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION Remove the instrument panel lower center trim panel. Refer to INSTRUMENT PANEL LOWER CENTER TRIM PANEL REPLACEMENT Remove the radio control bracket. Refer to RADIO CONTROL MODULE REPLACEMENT 1 Heater and Air Conditioning Control Procedure Disconnect the heater and air conditioning control electrical connector Use a flat-bladed plastic trim tool, to remove the heater and air conditioning control from the instrument panel lower center trim panel

Heater and Blower and Air Conditioning Control Module Replacement

Calout Component Name Preliminary Procedures 1. Remove the instrument panel compartment. Refer to INSTRUMENT PANEL COMPARTMENT REPLACEMENT 2. Remove the floor air outlet duct. Refer to FLOOR AIR OUTLET DUCT REPLACEMENT - RIGHT SIDE 3. Disconnect the heater and blower and air conditioning control module electrical connectors 1 Heater and Blower and Air Conditioning Control Module Fastener (Qty: 2) 2 Heater and Blower and Air Conditioning Control Module

Heater and Air Conditioning Remote Control Replacement

Calout Component Name Preliminary Procedures Remove the instrument panel upper center trim panel. Refer to INSTRUMENT PANEL UPPER CENTER TRIM PANEL REPLACEMENT 1 1 Un-latch the heater and air conditioning remote control 2 Disconnect the heater and air conditioning remote control module connectors 3. Perform the heater and air conditioning remote control module programming, and setup procedure. Refer to HVAC SYSTEM CONTROL MODULE PROGRAMMING AND SETUP . 4. Perform the actuator re-calibration procedure. Refer to ACTUATOR RECALIBRATION

Temperature Valve Actuator Replacement - Left Side

Calout Component Name Preliminary Procedures 1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION 2. Remove the instrument panel lower trim panel - driver side. Refer to INSTRUMENT PANEL LOWER TRIM PANEL REPLACEMENT - LEFT SIDE 3. Remove the floor air outlet duct - left side. Refer to FLOOR AIR OUTLET DUCT REPLACEMENT - LEFT SIDE 1 Temperature Valve Actuator Fastener (Qty: 2) Procedure Disconnect the temperature actuator electrical connector. 2 Temperature Valve Actuator Tip Actuator is self-calibrating when connecting the battery

Mode Valve Lever Replacement

Calout Component Name Preliminary Procedures 1. Remove the mode control cam actuator. Refer to Mode Control Cam Actuator Replacement 2. Remove the instrument cluster. Refer to INSTRUMENT CLUSTER REPLACEMENT 3. Remove the mode control cam. Refer to Mode Control Cam Replacement 1 Mode Valve Lever Procedure Move the valve to the middle position and mark the position of the mode valve lever notch to the mode valve gear. Tip Use the indentation for the correct positioning of the lever arms

Mode Valve Gear Replacement

Calout Component Name Preliminary Procedures 1. Remove the mode control cam actuator. Refer to Mode Control Cam Actuator Replacement 2. Remove the instrument cluster. Refer to INSTRUMENT CLUSTER REPLACEMENT 3. Remove the mode control cam. Refer to Mode Control Cam Replacement 1 Mode Valve Lever Procedure 1. Move the valve to the middle position and mark the position of the mode valve lever notch to the mode valve gear 2. Remove the mode valve lever 2 Mode Valve Gear Procedure Release and remove the mode valve gear Tip 1. When replacing the valve gear, transfer the mark to the new part 2. The mode valve gear can only be fitted in one position 3. Use the indentation for the correct positioning of the lever arms

Inside Air Valve Actuator Replacement

Calout Component Name Preliminary Procedures 1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION 2. Remove air inlet housing assembly. Refer to AIR INLET HOUSING REPLACEMENT 1 Inside Air Valve Actuator Fastener (Qty: 2) 2 Inside Air Valve Actuator Procedure Disconnect the inside air valve actuator electrical connector Note: The actuator is self-calibrating when connecting the battery

Mode Control Cam Replacement

Calout Component Name Preliminary Procedures 1. Remove the instrument panel lower trim panel - driver side. Refer to INSTRUMENT PANEL LOWER TRIM PANEL REPLACEMENT - LEFT SIDE 2. Remove the floor air outlet duct - driver side. Refer to FLOOR AIR OUTLET DUCT REPLACEMENT - LEFT SIDE 3. Remove the mode control cam actuator. Refer to Mode Control Cam Actuator Replacement 1 Mode Control Cam Procedure 1. Release and pull off the control cam 2. The mode control cam can only be fitted in one position

Mode Control Cam Actuator Replacement

Calout Component Name Preliminary Procedures 1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION 2. Remove the instrument panel lower trim panel - left side. Refer to INSTRUMENT PANEL LOWER TRIM PANEL REPLACEMENT - LEFT SIDE 3. Remove the floor air outlet duct - left side. Refer to FLOOR AIR OUTLET DUCT REPLACEMENT - LEFT SIDE 1 Mode Control Cam Actuator Fastener (Qty: 2) Procedure Disconnect the mode control cam actuator electrical connector 2 Mode Control Cam Actuator Tip The actuator is self-calibrating when connecting the battery

Air Inlet Valve Actuator Replacement

Calout Component Name Preliminary Procedures 1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION 2. Remove the air inlet housing assembly. Refer to AIR INLET HOUSING REPLACEMENT 1 Air Inlet Valve Actuator Fastener (Qty: 2) 2 Air Inlet Valve Actuator Procedure Disconnect the air inlet valve actuator electrical connector Note: The actuator is self-calibrating when connecting the battery

Ambient Air Quality Sensor Replacement

Calout Component Name Preliminary Procedures Remove air inlet panel water deflector. Refer to AIR INLET GRILLE PANEL WATER DEFLECTOR REPLACEMENT 1 Ambient Air Quality Sensor Procedure 1. Unsnap the ambient air quality sensor and move it forward 2. Disconnect the electrical connector

Ambient Air Temperature Sensor Replacement

Calout Component Name 1 Ambient Air Temperature Sensor Procedure Disconnect the electrical connector

Inside Air Moisture and Windshield Temperature Sensor Replacement

Calout Component Name 1 Inside Rear Mirror Mount Plate Cover Procedure Unsnap the inside rear mirror mount plate cover from the windshield inside rear mirror cover bracket 2 Inside Air Moisture and Windshield Temperature Sensor Procedure 1. Disconnect the electrical connector 2. Pull down the inside air moisture and windshield temperature sensor out slightly, and slide out from the inside rear mirror cover bracket

Air Conditioning Refrigerant Temperature Sensor Replacement

Calout Component Name Preliminary Procedures 1. Remove instrument panel compartment. Refer to INSTRUMENT PANEL COMPARTMENT REPLACEMENT 2. Remove the floor air outlet duct - right side. Refer to FLOOR AIR OUTLET DUCT REPLACEMENT - RIGHT SIDE 1 Air Conditioning Refrigerant Temperature Sensor Procedure 1. Disconnect the refrigerant temperature sensor electrical connector 2. Twist and pull the refrigerant temperature sensor from the HVAC module assembly

Manual HVAC Description and Operation

The air temperature and the air delivery description and operation are divided into eight areas

1. HVAC Control Components
2. Air Speed
3. Air Delivery
4. Heating and A/C Operation
5. Recirculation Operation
6. Engine Coolant
7. A/C Cycle

HVAC Controls

The HVAC controls contains all switches, which are required to control the functions of HVAC and serve as interface between the operator and the HVAC control module. The selected values are passed to the HVAC control module via LIN-Bus.

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain and control desired air temperature and air distribution settings. The battery positive voltage circuit provides power that the HVAC control module uses for keep alive memory. If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from keep alive memory. The body control module (BCM), which is the vehicle mode master, provides a device ON-Signal. The HVAC control module provides blower, air delivery mode and air temperature settings. The HVAC control module supports the following features

HVAC CONTROL MODULE FEATURES

Mode Actuator

The mode actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the mode flap into the calculated position in order to reach the selected position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Air Temperature Actuator

The air temperature actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The air temperature actuator puts the mixed air flap into the calculated position, in order to reach the selected temperature of the temperature switch. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the coil to reach exactly the desired position of the flap.

Recirculation Actuator

The recirculation actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the recirculation flap into the calculated position in order to reach the desired position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Blower Motor Control Module

The blower motor control module controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a low side pulse width modulation (PWM) signal to the blower motor control module via the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.

Evaporator Temperature Sensor

The evaporator temperature sensor is a 2-wire negative temperature co-efficient thermistor. The sensor operates within a temperature range of -40 to +85°C (-40 to +185°F). The sensor is installed at the evaporator and measures its temperature. If the temperature drops under 3°C (38°F), the compressor will be switched off in order to prevent a frozen evaporator.

A/C Refrigerant Pressure Sensor

The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. The 5 V reference voltage, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0.2-4.8 V. When the A/C refrigerant pressure is low, the signal value is near 0 V. When the A/C refrigerant pressure is high, the signal value is near 5 V. The engine control module (ECM) converts the voltage signal to a pressure value. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to engage.

A/C Compressor

This A/C system uses a conventional clutch to engage and mechanically turn the compressor, and a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both a constant battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid valve using a (PWM) signal in order to determine the amount of compressor displacement. The performance of the A/C compressor is regulated according to adjusted interior temperature.

Air Speed

The blower control switch is part of the HVAC controls. The selected value of the blower switch position is sent to the HVAC control module via LIN-Bus.

The blower motor control module is an interface between HVAC control module and blower motor. The blower motor control module regulates supply voltage and ground circuits to blower motor. The HVAC control module provides a PWM signal to the blower motor control module in order to command the desired blower motor speed. The blower motor control module supplies battery voltage to the blower motor and uses the blower motor ground as a low side control to adjust the blower motor speed. The voltage amounts between 2-13 V and changes linear to the height of the PWM signal.

Air Delivery

The HVAC control module controls the distribution of air by the use of recirculation and mode actuator. The modes that may be selected are

1. Defrost
2. Defog
3. Panel
4. Floor

The desired air distribution mode can be selected with the air distribution switches at the HVAC controls. The HVAC controls delivers the values to the HVAC control module via LIN-Bus. The HVAC control module controls the air distribution actuator so that it drives the flap to the calculated position. Depending on the position of the flap, air is distributed through various ducts leading to the outlets in the dash. Turning the mode flap to the defrost position, the HVAC control module will move the recirculation actuator to outside air, reducing window fogging. When defrost is selected, the blower motor will be activated, regardless of the coolant temperature. The HVAC control module enables a high volume of air delivered to the front defrost vents. A/C is available in all modes.

The rear window defogger does not affect the HVAC system.

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. Regardless of the temperature setting, the following can affect the rate that the HVAC system can achieve the desired temperature

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

When the A/C switch is pressed, the HVAC controls sends a signal to the HVAC control module via LIN-Bus. The HVAC control module evaluates this signal and sends an A/C request signal to the ECM via CAN-Bus. The ECM checks all preconditions before releasing and if all conditions are met sends a release signal back to the HVAC control module.

The following conditions must be met in order to activate the A/C compressor

1. Battery voltage is between 9-18 V
2. Engine coolant temperature is less than 124°C (255°F)
3. Engine speed is greater than 600 RPM
4. Engine speed is less than 5500 RPM
5. A/C high side pressure is between 269-2929 kPa (39-425 PSI)
6. Throttle position is less than 100%
7. Evaporator temperature is greater than 3°C (38°F)
8. ECM does not detect immoderate torque load
9. ECM does not detect insufficient idle quality
10. The ambient temperature is above 1°C (34°F)

The sensor information is used by the ECM to determine the following

1. The A/C high side pressure
2. An A/C system load on the engine
3. An immoderate A/C high side pressure
4. The heat load at the A/C condenser

The air streams into the passenger compartment through the heater core and the evaporator core. The air temperature actuator drives the mixed air flap to determine the path of the incoming air. If the interior temperature should be increased, the mixed air flap is put into the position in which more air streams through the heater core. If the interior temperature should be decreased, the mixed air flap is put into the position in which more air streams through the evaporator core.

Recirculation Operation

The recirculation switch is integrated into the HVAC controls. The selected recirculation switch position is sent to the HVAC control module via LIN-Bus. The HVAC control module controls the air intake through the air inlet actuator and recirculation actuator. In the recirculation mode the air inlet flap closes and the recirculation flap opens in order to circulate the air within the vehicle. In fresh air mode the air inlet flap opens and the recirculation flap is closed again in order to route outside air into the vehicle. Recirculation is only available if the defrost mode is not active. When the defrost mode is active, the recirculation actuator opens the recirculation flap and the air inlet actuator opens the air inlet flap and outside air is circulated to the windshield to reduce fogging.

Engine Coolant

Engine coolant is the essential element of the heating system. The thermostat controls the normal engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation.

Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC module. The ambient air drawn through the HVAC module absorbs the heat of the coolant flowing through the heater core. Heated air is distributed to the passenger compartment, through the HVAC module, for passenger comfort. Opening or closing the air temperature flap controls the amount of heat delivered to the passenger compartment. The coolant exits the heater core through the return heater hose and recirculates back to the engine cooling system.

A/C Cycle

Refrigerant is the key element in an air conditioning system. R-134a is presently the only Environmental Protection Agency 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.

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 A/C refrigerant pressure sensor fails 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 to the Receiver/Dehydrator(R/D).

The R/D contains desiccant that absorbs moisture that may be in the refrigerant system. The R/D also acts as a storage vessel to ensure that a steady flow of liquid reaches the Thermal Expansion Valve. The refrigerant exits the R/D and flows through the liquid line to the Thermal Expansion Valve.

The Thermal Expansion Valve is located at the front of dash and attaches to the evaporator inlet and outlet pipes. 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 on the refrigerant is lowered. 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 through the suction line and back to the A/C compressor, in a vapor state, and completing the A/C cycle of heat removal. At the A/C 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.

See also:
• BLOWER MOTOR REPLACEMENT
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• TESTING FOR INTERMITTENT CONDITIONS AND POOR CONNECTIONS
• COMPONENT CONNECTOR END VIEWS -- INDEX
• Circuit Testing
• Connector Repairs
• Wiring Repairs
• Diagnostic Repair Verification
• Control Module References
• CHECKING AFTERMARKET ACCESSORIES
• AIR CONDITIONING (A/C) SYSTEM PERFORMANCE TEST
• HEATING PERFORMANCE DIAGNOSTIC
• BATTERY NEGATIVE CABLE DISCONNECTION AND CONNECTION
• INSTRUMENT PANEL LOWER CENTER TRIM PANEL REPLACEMENT
• RADIO CONTROL MODULE REPLACEMENT
• HVAC SYSTEM CONTROL MODULE PROGRAMMING AND SETUP
• ACTUATOR RECALIBRATION
• INSTRUMENT CLUSTER REPLACEMENT
• AIR INLET GRILLE PANEL WATER DEFLECTOR REPLACEMENT
• Inside Air Valve Actuator Replacement
• Temperature Valve Actuator Replacement - Left Side
• Mode Control Cam Actuator Replacement
• Air Conditioning Refrigerant Temperature Sensor Replacement
• Heater and Air Conditioning Control Replacement
• Heater and Blower and Air Conditioning Control Module Replacement
• Heater and Air Conditioning Remote Control Replacement
• DTC B0193
• Manual HVAC Description and Operation
• HVAC Component Replacement Reference
• Mode Control Cam Actuator Replacement