HVAC System - Automatic: Other Chevrolet Volt I

Sensor Resistance Table

Sensor Resistance Table

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

Scan Tool Reference

Control Module References for scan tool information

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Vehicle in Service Mode, HVAC system turned ON.
2. Verify the scan tool Auxiliary Heater Coolant Pump Command parameter is between 20%-90%. If the Auxiliary Heater Coolant Pump Command parameter is not between 20%-90%. Refer to Circuit/System Testing If the Auxiliary Heater Coolant Pump Command parameter is between 20%-90%.
3. Verify the scan tool Auxiliary Heater Coolant Pump Feedback parameter is between 40%-60%. If the Auxiliary Heater Coolant Pump Feedback parameter is not between 40%-60%. Refer to Circuit/System Testing If the Auxiliary Heater Coolant Pump Feedback parameter is between 40%-60%.
4. All OK

Perform the Diagnostic Repair Verification after completing the repair.

1. «Heater Water Auxiliary Pump Replacement»(ref-487454-S20162981302012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the repair.

1. «Ambient Air Temperature Sensor Replacement»(ref-487453-S32209118362012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for Hybrid/EV Powertrain Control Module 2 replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode.
2. Verify the scan tool engine control module A/C High Side Pressure Sensor parameter is between.25 V and 4.75 V. If the parameter is not between.25 V and 4.75 V. Refer to Circuit/System Testing. If the parameter is between.25 V and 4.75 V
3. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for engine control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Verify that DTC P1EC3 is not set. If the DTC is set, Refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-487438-S15134519352012072300000) .
2. Verify that DTC P0534 is not set. If the DTC is set, Refer to «Air Conditioning (A/C) System Performance Test»(ref-487454-S04315931872012072300000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

1. «Automatic HVAC Description and Operation»(ref-487453-S11426883382012072300000)
2. «Heating and Air Conditioning System Description and Operation»(ref-487454-S23184652162012072300000)

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for hybrid powertrain control module 2 control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode
2. Verify that DTC's P0D69-P0D7F are not set. If any of the DTC's are set Program the G1 A/C compressor control module and the K114B Hybrid/EV powertrain control module 2 with the latest software calibration. Verify the DTC's do not set If any of the DTC's set, replace the affected control module. Refer to «High Voltage Disabling»(ref-487464-S39476959352012072300000) If none of the DTC's are set All OK If none of the DTC's are set
3. All OK

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-48900 HEV Safety Kit

For equivalent regional tools, refer to Special Tools .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Inverter)»(ref-487464-S19854998962012072300000) , «300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-Charger)»(ref-487464-S15030588122012072300000) , «300-Volt Battery Positive and Negative Cable Replacement (Inverter-to-Compressor/Heater Module)»(ref-487464-S14385611242012072300000) , «300-Volt Battery Positive and Negative Cable Replacement (Drive Motor Battery-to-APM Module)»(ref-487464-S11543033732012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for coolant heater control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for control module replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

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 diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for ECM replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode
2. Verify that DTC's P0F0A-P1F0D are not set. If any of the DTC's are set Program the G1 A/C compressor control module and the K114B Hybrid/EV powertrain control module 2 with the latest software calibration. Verify the DTC's do not set If any of the DTC's set, replace the affected control module. Refer to «High Voltage Disabling»(ref-487464-S39476959352012072300000) If none of the DTC's are set All OK If none of the DTC's are set
3. All OK

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for ECM replacement, programming and setup

Schematic Reference

HVAC Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode.
2. Verify that DTC P0606, P0CE7, P2518 or P26A7 is not set. If any of the DTCs are set Refer to «DTC P151C or P2516-P2518»(ref-487453-S06726516462012072300000) If none of the DTCs are set
3. Refer to Circuit/System testing

Perform the Diagnostic Repair Verification after completing the repair.

1. «Heater Water Shutoff Valve Replacement»(ref-487454-S13382584272012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for the hybrid powertrain control module 2 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-487438-S13406627192012072300000) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to «Automatic HVAC Description and Operation»(ref-487453-S11426883382012072300000) .

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

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-487461-S14472700752012072300000)
2. «Connector Repairs»(ref-487461-S16008896872012072300000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-487461-S02545222692012072300000)
4. «Wiring Repairs»(ref-487461-S20629117392012072300000)

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode.
2. Verify the scan tool Blower Motor Switch parameter changes when pressing the switch If the parameter does not change Replace the A20 radio/HVAC controls If the parameter changes
3. Verify that 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-487453-S05082104432012072300000) . 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 Switch Air Recirculation Mode Switch Bi-Level Switch If any parameter does not change Replace the A20 radio/HVAC controls If all parameters change
5. Vehicle ON, HVAC in comfort mode.
6. Verify the HVAC modes listed below change when pressing the appropriate switch. Temperature Bi-Level Mode Recirculation If any HVAC mode does not change Refer to «DTC B0223, B0233, B023A, or B0408»(ref-487453-S16716636752012072300000) . If all HVAC modes change
7. Verify cool air flows from the ducts with the temperature control in the coldest position. If the air is not cool Refer to «Air Conditioning (A/C) System Performance Test»(ref-487454-S04315931872012072300000) . If the air is cool
8. 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-487454-S38834244272012072300000) . If the air is warm
9. Vehicle in Service Mode
10. Verify the scan tool 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-487453-S18463384042012072300000) . If the Sunload parameter changes
11. 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 Temperature parameter. If greater than a 3°C (5°F) difference Refer to «DTC B0163»(ref-487453-S06675397302012072300000) . If less than a 3°C (5°F) difference
12. Verify the scan tool parameters listed below are less than 3°C (5°F) of the actual duct temperature. Lower Left Duct Air Temperature Upper Left Duct Air Temperature If 3°C (5°F) or greater Refer to «DTC B0173, B0178, or B3933»(ref-487453-S11360760722012072300000) . If less than 3°C (5°F)
13. Vehicle ON and A/C ON.
14. Verify the scan tool A/C Evaporator Temperature parameter is between -35°C (-39°F) and 85°C (185°F) and changes as the evaporator air temperature changes. If the parameter is not between -35°C (-39°F) and 85°C (185°F) Refer to «DTC P0536-P0538 or P153B»(ref-487453-S24593020982012072300000) . If the parameter is between -35°C (-39°F) and 85°C (185°F).
15. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

1. «HVAC Component Replacement Reference»(ref-487453-S10567932402012072300000)
2. «Control Module References»(ref-487462-S26106952412012072300000) for HVAC control module and radio/HVAC control replacement, programming and setup

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. Vehicle in Service Mode.
6. Wait 40 seconds 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 Remote Heater and Air Conditioning Control Module 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 seconds.
6. Install the HVAC control module fuse.
7. Vehicle in Service Mode.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

Scheme 6

Heater and Air Conditioning Remote Control Replacement

Scheme 7

Air Inlet Valve Actuator Replacement

Scheme 8

Mode Control Cam Actuator Replacement

Scheme 9

Temperature Valve Actuator Replacement

Scheme 10

Air Conditioning Refrigerant Temperature Sensor Replacement

Scheme 11

Duct Air Temperature Sensor Replacement - Upper

Scheme 12

Duct Air Temperature Sensor Replacement - Lower

Scheme 13

Ambient Air Temperature Sensor Replacement

Scheme 14

Inside Air Moisture and Windshield Temperature Sensor Replacement

Scheme 15

Sun Load Temperature and Headlamp Automatic Control Ambient Light Sensor 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 serial data.

HVAC Remote Control Module

The HVAC control module is a serial data 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 power 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 Coolant Pump

The HVAC control module will control a cabin coolant heater pump based on a valid flow rate. If the HVAC Heating system requests a coolant flow rate, the HVAC coolant pump will be commanded "on" and to the desired speed.

HVAC Cabin Coolant Sensor

The HVAC control module will monitor a coolant temperature sensor input. This will be used to determine the heat source requirements for the coolant heater control module. This input will also be used along with engine temperature and other vehicle inputs.

Mode Actuator

The mode actuator is a 5-pin 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-pin 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-pin 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.

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 close to 3°C (38°F), the A/C compressor will be commanded off by the HVAC control module in order to prevent icing of the evaporator.

A/C Refrigerant Temperature Sensor

The A/C refrigerant 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 in the low side refrigerant line and measures its temperature. If the temperature drops close to 3°C (38°F), the A/C compressor will be commanded off by the Hybrid/EV powertrain control module 2 in order to prevent icing of the evaporator.

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.

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.

A/C Compressor

The AC compressor function is to provide refrigerant flow in the AC refrigerant loop to help cool down the cabin, help dehumidify the air in a defrost mode and help maintain the battery temperature. Rather than a more-typical pulley, the A/C compressor uses a 3-phase alternating current, high voltage electric motor to operate. It has an on-board inverter that takes high voltage direct current from the vehicle's high voltage battery and inverts it to alternating current for the motor. The AC compressor shall be activated when any of the three following events occur

1. The customer pushes the AC button or
2. The HVAC control, in ECO climate or Comfort Climate Settings, requests the electric AC compressor on to help in cooling the cabin or removing moisture in conditions where the windows may fog or
3. The hybrid/EV powertrain control module 2 requests the AC compressor on to help maintain the battery temperature

The hybrid/EV powertrain control module 2 uses values from the A/C refrigerant pressure sensor, A/C refrigerant thermistor, duct temperature sensors, ambient air temperature sensor, passenger compartment temperature sensor, evaporator temperature sensor, battery cell temperature sensors, battery coolant temperature sensors and battery coolant pumps to determine the speed at which the compressor will operate. This message is sent from the hybrid/EV powertrain control module 2 to the A/C compressor control module via serial data message.

Air Speed

The blower control switch is part of the HVAC faceplate control. The selected value of the blower switch position is sent to the HVAC control module via serial data.

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 within the passenger compartment by the use of the mode actuator. The modes that may be selected are

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

In auto mode, the air delivery mode is controlled automatically based on cooling/warming needs of the compartment. The desired air distribution mode can be selected with the air distribution buttons at the HVAC faceplate control. The HVAC control delivers the values to the HVAC control module via serial data. The HVAC control module controls the mode 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. 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.

Coolant Heater Control Module

The coolant heater control module is an essential element of the hybrid heating system. The hybrid/EV powertrain control module 2 controls the passenger compartment heater coolant control valve, and the HVAC commands the coolant heater control module activation. Heated coolant either from the engine or the coolant heater control module will meet HVAC temperature demands. The coolant heater control module will be commanded "off" if the coolant temperature exceeds the desired temperature.

Coolant heat generated by the engine is also an element of the heating system. Once the engine coolant is warm enough to supply the required heat, the passenger compartment heater coolant control valve will move to the 'link' position, which allows sharing of coolant between the engine, the coolant heater control module and passenger compartment heater core. The coolant heater control module power level will be reduced and/or cycled on/off as the engine turns on/off during charge-sustaining mode, maintaining cabin comfort. When the engine is utilized for charge sustaining mode the thermostat will control 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.

Heater 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 system as controlled by the coolant passenger compartment heater coolant control valve.

A/C Compressor 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.

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. The HVAC control module blows air through the evaporator core. Warm and moist air will cause the liquid refrigerant to boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator through the suction line and back to the 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 through a drain to outside(underside) of the vehicle.

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.