HVAC System - Automatic: Other Saturn Aura I

Sensor Resistance Table (Inside Air Temperature Sensor)

Sensor Resistance Table (Ambient Air Temp Sensor)

The Tech 2 will display sensor value as a voltage. This gives the approximate voltage expected at different ambient temperatures as well as what should be read with an ohmmeter connected to the sensor. Since this is raw data any heat from underhood that changes ambient temp around the sensor might skew the reading, so let the engine compartment cool.

Sensor Resistance Table (Upper and Lower Duct Temp Sensors)

Sensor Resistance Table (Duct Temp conversion temp to counts)

Scheme 1

Scheme 2

Scheme 3

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)
2. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool HVAC Control Module Ambient Air Temp Sensor parameter. The reading should be between -35°C (-39°F) and 85°C (185°F) and change with air temperature changes.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «AMBIENT AIR TEMPERATURE SENSOR REPLACEMENT»(ref-301536-S16691963752008112400000)
2. «Control Module References»(ref-301518-S12838675482008101700000) for BCM replacement, setup, and programming

Inside Air Temperature Sensor

The inside air temperature sensor is internal to the HVAC control module.

Upper and Lower Air Duct Temperature Sensors

The HVAC control module supplies the air duct temperature sensors with a low reference circuit and 5-volt signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)
2. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Temperature Sensor Replacement - Upper»(ref-301490-S39889339412008101700000)
2. «Air Temperature Sensor Replacement - Lower»(ref-301490-S05807586802008101700000)
3. «Control Module References»(ref-301518-S12838675482008101700000) for HVAC control module replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)
2. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool Sunload Sensor parameter. The reading should be between 5 and 250 counts and change with sunlight changes.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Ambient Light Sensor Replacement»(ref-301486-S13004397982008101700000)
2. «Control Module References»(ref-301518-S12838675482008101700000) for BCM and HVAC control module replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)
2. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the appropriate actuator in both directions with a scan tool. The scan tool Door Position parameter reading should be between 5 and 250 counts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Recirculation Actuator Replacement»(ref-301490-S08411994072008101700000)
2. «Mode Actuator Replacement»(ref-301490-S35992142482008101700000)
3. «Air Temperature Actuator Replacement»(ref-301490-S29232235522008101700000)
4. «Control Module References»(ref-301518-S12838675482008101700000) for HVAC replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)
2. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool A/C High Side Pressure parameter in the ECM. The reading should be between 0.1-4.90 volts (1-425 psi), and change with pressure.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement»(ref-301492-S23964702212008101700000)
2. «Control Module References»(ref-301518-S12838675482008101700000) for ECM replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)
2. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Compressor Replacement (LY7)»(ref-301492-S06788641862008101700000) or «Compressor Replacement (LAT)»(ref-301492-S23678067222008101700000) or «Compressor Replacement (LE5)»(ref-301492-S39198958172008101700000) or «Compressor Replacement (LZ4)»(ref-301492-S03579280282008101700000)
2. «Relay Replacement (Attached to Wire Harness)»(ref-301519-S26584121562008101700000) or «Relay Replacement (Within an Electrical Center)»(ref-301519-S37718150942008101700000)
3. «Control Module References»(ref-301518-S12838675482008101700000) for HVAC control module and ECM replacement, setup, and programming

Symptoms - HVAC Systems - Automatic

1. Perform the «Diagnostic System Check - Vehicle»(ref-301515-S32423278442008101700000) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to: «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000) «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)

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

Air Temperature Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(ref-301519-S26584121562008101700000) or «Relay Replacement (Within an Electrical Center)»(ref-301519-S37718150942008101700000)
2. «Compressor Clutch Assembly Replacement»(ref-301492-S35334728772008101700000)
3. «Control Module References»(ref-301518-S12838675482008101700000) for ECM replacement, setup, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)
2. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the blower motor ON and OFF with a scan tool. Monitor/feel the operation of the blower motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Blower Motor Replacement»(ref-301492-S29666171512008101700000)
2. «Control Module References»(ref-301518-S12838675482008101700000) for HVAC control module replacement, setup, and programming

Air Temperature Sensors

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

1. Ambient air temperature sensor
2. Upper air temperature sensor
3. Lower air temperature sensor

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 +101°C (-40 to +215°F). The sensor signal varies between 0-5 volts. The input of the duct air temperature sensors are different from the ambient and inside air temperature sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Delivery Description and Operation»(ref-301490-S30400893532008101700000)
2. «Air Temperature Description and Operation»(ref-301490-S02095362792008101700000)

Electrical Information Reference

1. «Circuit Testing»(ref-301517-S12739748792008101700000)
2. «Connector Repairs»(ref-301517-S02286547552008101700000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-301517-S37460750252008101700000)
4. «Wiring Repairs»(ref-301517-S19995224182008101700000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, cover the sunload sensor assembly with a shop towel or other suitable item. Verify the scan tool Right Sunload Sensor and Left Sunload Sensor parameters are within 3 counts of each other. If not within the specified range, refer to «Circuit/System Testing»(ref-301490-S36963263222008101700000) Sun Load Sensor Circuit Malfunction.
2. Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Ambient Air Temp Sensor parameter. The measured temperature should be within 5 degrees of parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-301490-S36963263222008101700000) Ambient Air Temperature Sensor Circuit Malfunction.
3. Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5 degrees of appropriate Duct Actual parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-301490-S36963263222008101700000) Duct Temperature Sensor Circuit Malfunction.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Temperature Sensor Replacement - Upper»(ref-301490-S39889339412008101700000)
2. «Air Temperature Sensor Replacement - Lower»(ref-301490-S05807586802008101700000)
3. «Ambient Light Sensor Replacement»(ref-301486-S13004397982008101700000)
4. «Control Module References»(ref-301518-S12838675482008101700000) for HVAC 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. Select HVAC Module.
4. Select HVAC Systems Automatic.
5. Select BCM.
6. Select Module Setup.
7. Select Afterblow Option.
8. Upon selecting the afterblow option a asterix will appear next to the word afterblow meaning the function is enabled.
9. Select the save option in the lower left of the screen.

When afterblow has been enabled by the scan tool the blower motor will operate at 68 percent blower speed for 2 minutes 30 seconds to 4 minutes after the engine has been in Key OFF for 30 minutes.

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

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

Actuator Recalibration

When replacing an air temperature, mode, recirculation actuator or HVAC control module the following calibration process needs to be performed

1. Place the ignition switch to the OFF position.
2. Disconnect the battery.
3. Disconnect the scan tool.
4. Install the HVAC control module or appropriate actuator.
5. Connect all previously disconnected components.
6. Connect the battery.
7. Place the ignition switch to the ON position.
8. Calibration of the air temperature, recirculation and mode doors happens taking roughly 13 seconds.
9. Verify that no DTCs have set as current DTCs.

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from °C to °F by pressing the Auto button for a minimum of 3 seconds. The ignition 3 voltage circuit provides a device on signal. The control module supports the following features

Mode/Recirculation Actuator

The air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 12-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-12 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

Blower Motor Control Processor

The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

Air Speed

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position. The blower motor will only operate if the blower motor switch is in any position other than OFF, and the ignition switch is in the RUN position.

Once a blower speed is selected, the blower speed remains constant until a new speed is selected.

As the requested blower speed increases, the following conditions occur

1. The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.
2. The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.

As the requested blower speed decreases, the following conditions occur

1. The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.
2. The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.

Afterblow

Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned off. This reduces the amount of microbial growth that can create undesirable odors. The vehicle does not come equipped with the afterblow feature turned on. If the afterblow feature is required due to an odor concern, it must be turned on by the scan tool. Any C68 HVAC control head built before part number 25782408 will not support the afterblow enabling process. These control heads will need a reflash of the HVAC control head to update older software, then enabling of the afterblow process through the scan tool can be enabled.

The following conditions must be met for afterblow to operate

1. The A/C compressor operated during the latest key cycle.
2. The system voltage is at least 11 volts to start and 10 volts to continue to run.
3. The ignition has been in the OFF position for at least 30 minutes.

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

1. The blower will run for 150 seconds (2 minutes 30 seconds) at 68 percent blower speed.
2. The recirculation door moves to outside air position.
3. The mode valve moves to the floor position.

Air Distribution

The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet. The mode switch provides the vehicle operator with the ability to override the automatic setting. When the mode switch is moved to the bi-level through defrost positions, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. When VENT is pressed, the following will occur

1. The mode valve will be moved to the panel position.
2. The recirculation actuator will follow user request if blower is on and power mode is in run.
3. The A/C compressor will follow user request if blower is on and power mode is in run.

Radio Display

This vehicle is equipped with a driver information center (DIC) and it displays outside temperature through the radio display. For a better understanding of the outside air temperature sensor please refer to Driver Information Center (DIC) Description and Operation .

The Radio/IPC displays the outside air temperature value that it receives through a Low Speed GMLAN message. The scan tool has the ability to update the displayed ambient air temperature. The HVAC Manual Tech 2 shows the ambient air temperature sensor feedback voltage under Body and Accessories / Data Display / BCM. The HVAC Auto System there is a temperature reading under HVAC / Data Display / HVAC / Sensor Data. Both readings are unfiltered so it is possible that the temperature read on the tech 2 will differ from the temperature displayed on the DIC/Radio without there being a problem with the vehicle. The DIC/Radio only displays the reading being sent from the BCM. The outside air temperature value is displayed or updated under the following conditions

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from °C to °F by pressing the Auto button for a minimum of 3 seconds. The HVAC control module during defrost modes will change the A/C compressor LED status from on to off. The ignition 3 voltage circuit provides a device on signal or backup indication as to the vehicles wake up power mode. The control module supports the following features

Air Temperature Actuator

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

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

1. Ambient
2. Inside
3. Upper duct air temperature sensor
4. Lower duct air temperature sensor

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

The inside air temperature sensor is located within the HVAC control module. Replacement of this sensor involves the replacement of the HVAC control module. The inside air temperature sensor operates within a temperature range between -40 to +185°C (-40 to +365°F). If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. The ambient temperature sensor operates within a temperature range between -40 to +87.5°C (-40 to +189.5°F). The sensor signal is read by the body control module (BCM), scaled appropriately and transmitted to the HVAC control module through the Low Speed bus. If the sensor is shorted to ground, voltage, or an open, the system will operate using a signal scaled appropriately to allow the system to operate.

The duct temperature sensor temperature response is different from the ambient and inside sensors. 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 operates within a temperature range between -40 to +80°C (-40 to +176°F).

Sunload Sensor

The sunload sensor is a 2-wire photo diode. The vehicle uses a single sunload sensor. The sensor is integrated into the ambient light sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The sensor signal is read by the BCM, scaled appropriately and transmitted to the HVAC control module through the GM LAN Low Speed bus. Bright, or high intensity, light causes the vehicles inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

A/C Refrigerant Pressure Sensor

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

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

If the powertrain control module (PCM) or engine control module (ECM) detects a failure in the A/C refrigerant pressure sensor or A/C High Side Pressure sensor circuit, the GM LAN Low Speed bus message sent to the HVAC control module will be invalid.

The afterblow function is not enabled from the factory. To enable function the following must occur. As soon as ignition is turned OFF, and all active processes are complete, the controller is put into sleep or low power mode. A high voltage wakeup is generated on the low speed GMLAN by the BCM and the HVAC virtual network is activated. Embedded in GMLAN message is Afterblow control logic bit (Aftrblw_Active). The afterblow resides in the BCM. The BCM has a timer that tells the HVAC Control module to go to Hi blower. The HVAC afterblow function is used to eliminate the odor associated with A/C usage. The "After Blow" is a method where by the HVAC blower is run for a few minutes after the vehicle is turned OFF in order to physically blow off excess condensation and eliminate odors.

Replacement of the inside air temperature sensor means replacing the HVAC control module. The inside air temperature sensor is an integral part of the HVAC control module. The HVAC control module monitors the passenger compartment inside air temperature through an inside air temperature sensor. When the air is cold, the sensor resistance and the signal voltage are high. When the air is warm, the sensor resistance and the signal voltage are low. The HVAC control module requests A/C compressor clutch engagement and controls the air temperature actuator door positions in order to maintain the selected air temperature. The HVAC control module sends out a 5-volt reference signal to the inside air temperature sensor over the 5-volt reference circuit. A thermistor varies the reference voltage back to the HVAC control module through the low reference circuit. The sensor is capable of sensing a temperature range of -40 to +85°C (-40 to +185°F).