HVAC System - Automatic: Other Chevrolet Cruze I facelift

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup.

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming, and setup.

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for engine control module (ECM) replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for engine control module replacement, programming and setup

Symptoms - HVAC Systems - Automatic

Note. The following steps must be completed before using the symptom tables

1. Perform the «Diagnostic System Check - Vehicle»(ref-543818-S13847936952013042400000) before using the HVAC System Malfunction procedure 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 «Automatic HVAC Description and Operation»(ref-543840-S24162287892013042400000) .

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. 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

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J43600 ACR Air Conditioning Service Center

Circuit/System Verification

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. If the parameter does not change for each speed position Replace the A26 HVAC Controls. If the parameter changes for each speed position
3. Verify the blower motor operates properly with the blower motor switch in each speed position. If the blower motor does not operate in each speed position Refer to «DTC B0193»(ref-543840-S05304872662013042400000) . If the blower motor operates properly in each speed position
4. Verify the scan tool parameters listed below change when pressing the appropriate switch. Left Temperature Right Temperature 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 Air Quality Sensor parameter changes while introducing hydrocarbons from a suitable source into the vicinity of the B108 Air Quality Sensor. If the Air Quality Sensor parameter does not change Refer to «DTC B3843»(ref-543840-S33224158832013042400000) . If the Air Quality Sensor parameter changes
6. 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»(ref-543840-S26294619212013042400000) . If all HVAC doors move
7. Install the J43600 ACR Air Conditioning Service Center.
8. 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. If the reading is not within 10% Refer to «DTC P0530, P0532, or P0533»(ref-543840-S40789051512013042400000) . If the reading is within 10%
9. Verify the A/C High Side Pressure Sensor parameter is between 269-2929 kPa (39-425 PSI). If the reading is not between 269-2929 kPa (39-425 PSI) Refer to «Air Conditioning (A/C) System Performance Test»(ref-543813-S16516712412013042400000) If the reading is between 269-2929 kPa (39-425 PSI)
10. Verify the scan tool parameters listed below are within 10% of ambient temperature. Lower Left Duct Air Temperature Sensor Upper Left Duct Air Temperature Sensor A/C Evaporator Temperature Sensor If not within 10% of ambient temperature Refer to «DTC B0173, B0178, or B3933»(ref-543840-S00557868602013042400000) . If within 10% of ambient temperature
11. Verify the scan tool Windshield Temperature parameter is within 10% of ambient temperature. If not within 10% of ambient temperature Refer to «DTC B018A, B048C, B048F, or B1395»(ref-543840-S01498680812013042400000) . If within 10% of ambient temperature
12. Verify the scan tool Passenger Compartment Humidity parameter is within 10% of actual humidity. If not within 10% of actual humidity Refer to «DTC B018A, B048C, B048F, or B1395»(ref-543840-S01498680812013042400000) . If within 10% of actual humidity
13. Engine ON, A/C system ON
14. Verify cool air flows from the ducts with the temperature control in the coldest position. If the air is not cool Verify the Q2 A/C Compressor Clutch is engaged. If the Q2 A/C Compressor Clutch is not engaged, refer to «Air Conditioning Compressor Malfunction»(ref-543840-S27294782292013042400000) . If the Q2 A/C Compressor Clutch is engaged, refer to «Air Conditioning (A/C) System Performance Test»(ref-543813-S16516712412013042400000) , and «DTC B393B»(ref-543840-S26633099732013042400000) . If the air is cool
15. Verify warm air flows from the ducts with the temperature control in the warmest position. If the air is not warm Refer to «Heating Performance Diagnostic»(ref-543813-S32261617562013042400000) . If the air is warm
16. Engine OFF, ignition ON.
17. Verify the Sunload parameter changes while covering the B10B Ambient Light/Sunload Sensor with a shop towel or other suitable item. If the Sunload parameter does not change Refer to «DTC B0183»(ref-543840-S28249448342013042400000) . If the Sunload parameter changes
18. Verify the actual inside air temperature, using a thermometer, is less than 3°C (5°F) difference from the scan tool Inside Passenger Compartment Air Temp. Sensor parameter. If greater than a 3°C (5°F) difference Refer to «DTC B0163»(ref-543840-S38349807662013042400000) . If less than a 3°C (5°F) difference
19. Verify the vehicle is equipped with an E40 Electrical Auxiliary Heater (C32). If the vehicle is not equipped with an E40 Electrical Auxiliary Heater (C32) Refer to step 21. If the vehicle is equipped with an E40 Electrical Auxiliary Heater (C32)
20. Verify the E40 Electrical Auxiliary Heater (C32) turns On and Off when commanding the Auxiliary Heater Request On and Off with a scan tool. If the E40 Electrical Auxiliary Heater (C32) does not turn On and Off Refer to . If the E40 Electrical Auxiliary Heater (C32) does turn On and Off
21. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-543840-S13677157822013042400000)
2. «Control Module References»(ref-543823-S31978628992013042400000) for HVAC control module replacement, programming, and setup.

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-543822-S09065750572013042400000)
2. «Connector Repairs»(ref-543822-S34024840292013042400000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-543822-S12370792452013042400000)
4. «Wiring Repairs»(ref-543822-S31020379062013042400000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming

Afterblow Enabling

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

Use the following procedure in order to enable the afterblow mode

1. Connect the Scan Tool.
2. Turn ON the ignition, with the engine OFF.
3. Build the vehicle with the scan tool.
4. Select Module Diagnosis.
5. Select Remote Heater and Air Conditioning Control Module.
6. Select Configuration/Reset Functions.
7. Select HVAC Afterblow Configuration.

When afterblow has been enabled by the scan tool the blower motor will operate at 68% blower speed, following the sequence below up to 5 times. This could last up to an hour

1. The blower motor will be OFF for 7-11 minutes.
2. The blower motor will RUN for 25-30 seconds.

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

1. The engine must be turned off for at least 30 min.
2. The outside air temperature must be at least 21°C (70°F).
3. The A/C compressor must have operated for more than 2 minutes before shut down during the latest key cycle.
4. The system voltage must be at least 12 V.

Actuator Recalibration

Note. Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

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

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

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

Preferred Method (with Scan Tool)

1. Clear all DTCs.
2. Place the ignition switch in the OFF position.
3. Install the HVAC actuator.
4. Connect all previously disconnected components.
5. Start the vehicle.
6. With the scan tool, initiate the HVAC Actuators re-calibration feature of the Heating and Air Conditioning Special Functions menu.
7. Verify that no DTCs have set as current DTCs.

Alternate Method (without Scan Tool)

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

Scheme 59

Heater and Air Conditioning Control Replacement

Scheme 60

Heater and Air Conditioning Remote Control Replacement

HVAC Control Components

HVAC Control

The HVAC control 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

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 stepper motor puts the mixed air flap into the calculated position, in order to reach the selected temperature. 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.

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 Processor

The blower motor control processor 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 processor 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.

Air Quality Sensor

The HVAC control module detects exhaust gas by an air quality sensor. The air quality sensor is a 3-wire sensor with an ignition voltage circuit, a ground circuit and a signal circuit. The HVAC control module evaluates the information of the air quality sensor and closes the recirculation flap, while the air quality sensor switch is pressed, as soon as the concentration of pollutants exceeds a predefined value.

Duct Temperature Sensors

The air temperature sensors are 2-wire negative temperature co-efficient thermistors. The sensors operate within a temperature range of -40 to +85°C (-40 to +185°F). The sensors are installed in the air distribution ducts and measure the temperature of the air that streams from the ducts. The HVAC control module uses these values to calculate the mixed air flap position.

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. A 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 does not use a conventional clutch to engage the compressor. It uses only 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.

Windshield Temperature and Inside Moisture Sensor

The windshield temperature and inside moisture sensor includes the relative humidity sensor, windshield temperature sensor and humidity sensing element temperature sensor.

This sensor assembly provides information about

1. Relative humidity level at windshield (compartment side)
2. Temperature of the windshield inside (compartment side)
3. Temperature of the humidity sensor element

The relative humidity sensor measures the relative humidity of the compartment side of the windshield. It also detects the temperature of the windshield surface on the passenger compartment side. Both values are used as control inputs for the HVAC control module application to calculate the fog risk on windshield compartment side and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield. The humidity sensor element temperature sensor supplies the temperature of the humidity sensor element. It is only needed if the thermal contact between the humidity sensing element and the inside windshield surface is not sufficient.

Ambient Light/Sunload Sensor

The ambient light/sunload sensor includes the sunload sensor and passenger compartment temperature sensor.

This sensor assembly provides information about

1. Sun heat intensity
2. Passenger compartment temperature

The solar sensor is connected to ground and to a 5 V stabilized voltage supply through the HVAC control module. As the sunload increases, the sensor signal voltage also increases and vice versa. The signal varies between 1.4-4.5 V and is provided to the HVAC control module.

The passenger compartment temperature sensor is a negative temperature co-efficient thermistor. A signal and low reference circuit enables the sensor to operate. As the air temperature increases, the sensor resistance decreases. The sensor signal varies between 0-5 V.

Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Air Speed

The blower control switch is part of the HVAC control. 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 control. The HVAC control 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.

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 control module. The ambient air drawn through the HVAC control module absorbs the heat of the coolant flowing through the heater core. Heated air is distributed to the passenger compartment, through the HVAC control 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 (TXV). The refrigerant exits the R/D and flows through the liquid line to the TXV.

The TXV is located at the front of dash and attaches to the evaporator inlet and outlet pipes. The TXV is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the TXV, the pressure on the refrigerant is lowered. The TXV also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the TXV flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC control 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 control 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 control module as water.