HVAC - Automatic: Other Hummer H2 I рестайлинг

Sensor Resistance Table

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)
2. «Air Delivery Description and Operation»(ref-299165-S20067632312008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Outside Air Temp. Raw parameter. The measured temperature should be within 5 degrees of parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-299165-S25778939782008092200000) for Ambient/Inside Air Temperature Sensor Circuit Malfunction.
2. Measure actual inside air temperature using a thermometer. Compare this value to the scan tool Inside Air Temp. parameter. The measured temperature should be within 5 degrees of parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-299165-S25778939782008092200000) for Ambient/Inside 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-299165-S25778939782008092200000) for Duct Temperature/Evaporator Temperature Sensor Circuit Malfunction.
4. Measure actual temperature using a thermometer at the A/C evap. temperature sensor. Compare this value to the scan tool A/C Evap. Temperature Sensor parameter. The measured temperature should be within 5 degrees of the parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-299165-S25778939782008092200000) for Duct Temperature/Evaporator Temperature Sensor Circuit Malfunction.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Temperature Sensor Replacement - Upper Right Side»(ref-299165-S23238907202008092200000)
2. «Air Temperature Sensor Replacement - Upper Left Side»(ref-299165-S24792941312008092200000)
3. «Air Temperature Sensor Replacement - Lower Left Side»(ref-299165-S26096246072008092200000)
4. «Air Temperature Sensor Replacement - Lower Right Side»(ref-299165-S23971466242008092200000)
5. «Ambient Air Temperature Sensor Replacement»(ref-299165-S26937068122008092200000)
6. «Inside Air Temperature Sensor Replacement»(ref-299165-S23920662532008092200000)
7. «Control Module References»(ref-299148-S19965029262008092200000)

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)
2. «Air Delivery Description and Operation»(ref-299165-S20067632312008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for Scan Tool Information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Ambient Light Sensor Replacement»(ref-299113-S17775713832008092200000)
2. «Control Module References»(ref-299148-S19965029262008092200000) 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 Delivery Description and Operation»(ref-299165-S20067632312008092200000)
2. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

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 3 and 253 counts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Recirculation Actuator Replacement»(ref-299165-S16108390952008092200000)
2. «Mode Actuator Replacement»(ref-299165-S38800245982008092200000)
3. «Air Temperature Actuator Replacement - Left Side»(ref-299165-S06733562262008092200000)
4. «Air Temperature Actuator Replacement - Right Side»(ref-299165-S19369758982008092200000)
5. «Temperature Valve Actuator Replacement - Auxiliary (Auxiliary)»(ref-299165-S25068477652008092200000)
6. «Mode Valve Actuator Replacement - Auxiliary»(ref-299165-S06179595422008092200000)
7. «Control Module References»(ref-299148-S19965029262008092200000) for HVAC control module and HVAC auxiliary control module or rear seat audio (RSA) replacement, setup, and programming

Schematic Reference

HVAC Schematics

Description and Operation

1. «Air Delivery Description and Operation»(ref-299165-S20067632312008092200000)
2. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for Scan Tool Information

Ignition ON, observe the scan tool A/C High Side Pressure Sensor parameter. The reading should be between 1 psi and 428 psi.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement»(ref-299130-S23209216762008092200000)
2. «Control Module References»(ref-299148-S19965029262008092200000) for ECM replacement, setup, and programming

Symptoms - HVAC Systems - Automatic

1. Perform the «Diagnostic System Check - Vehicle»(ref-299145-S35517489322008092200000) , before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control module 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-299165-S20067632312008092200000) «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)

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

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for Scan Tool Information

1. Ignition ON, Engine running
2. Press the A/C request switch. The A/C compressor clutch should engage.
3. Place the mode switch in the defrost position. The A/C compressor clutch should engage.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Compressor Replacement»(ref-299130-S02487172852008092200000)
2. «Compressor Clutch Plate/Hub Assembly Replacement»(ref-299130-S11563037262008092200000)
3. «Control Module References»(ref-299148-S19965029262008092200000) for HVAC control module and ECM replacement, setup, and programming

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 and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the blower motor speed 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 or low reference 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.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)
2. «Air Delivery Description and Operation»(ref-299165-S20067632312008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for Scan Tool Information

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Blower Motor Control Module Replacement»(ref-299130-S13160243172008092200000)
2. «Blower Motor Replacement»(ref-299130-S28639474752008092200000)
3. «Control Module References»(ref-299148-S19965029262008092200000) for ECM, and HVAC control module setup, replacement, and programming

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

1. «Air Delivery Description and Operation»(ref-299165-S20067632312008092200000)
2. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the auxiliary blower motor ON and OFF with a scan tool. Observe that the auxiliary blower motor turns ON and OFF with each command.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Auxiliary Blower Control Module Replacement»(ref-299130-S37130365462008092200000)
2. «Auxiliary Blower Motor Replacement»(ref-299130-S30081432532008092200000)
3. «Control Module References»(ref-299148-S19965029262008092200000) 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 Delivery Description and Operation»(ref-299165-S20067632312008092200000)
2. «Air Temperature Description and Operation»(ref-299165-S23987229322008092200000)

Electrical Information Reference

1. «Circuit Testing»(ref-299147-S03573486312008092200000)
2. «Connector Repairs»(ref-299147-S42810647942008092200000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
4. «Wiring Repairs»(ref-299147-S14041193842008092200000)

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-299165-S35731749972008092200000) for Sun Load Sensor Circuit Malfunction.
2. Remove the shop towel and shine a flashlight on the sunload sensor assembly. 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-299165-S35731749972008092200000) for Sun Load Sensor Circuit Malfunction.
3. Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Outside Air Temp. Raw parameter. The measured temperature should be within 5 degrees of parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-299165-S35731749972008092200000) for Ambient / Inside Air Temperature Sensor Circuit Malfunction.
4. Measure actual inside air temperature using a thermometer. Compare this value to the scan tool Inside Air Temp. parameter. The measured temperature should be within 5 degrees of parameter. If not within the specified range, refer to «Circuit/System Testing»(ref-299165-S35731749972008092200000) for Ambient / Inside Air Temperature Sensor Circuit Malfunction.
5. 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-299165-S35731749972008092200000) for Duct Temperature Sensor Circuit Malfunction.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Temperature Sensor Replacement - Upper Right Side»(ref-299165-S23238907202008092200000)
2. «Air Temperature Sensor Replacement - Upper Left Side»(ref-299165-S24792941312008092200000)
3. «Air Temperature Sensor Replacement - Lower Left Side»(ref-299165-S26096246072008092200000)
4. «Air Temperature Sensor Replacement - Lower Right Side»(ref-299165-S23971466242008092200000)
5. «Ambient Light Sensor Replacement»(ref-299113-S17775713832008092200000)

Actuator Recalibration

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 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 (w/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 Motor Re-calibration feature of the Heating and Air Conditioning Special Functions menu.
7. Verify that no DTCs have set as current DTCs.

Alternate Method (w/o 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/ECAS fuse for a minimum of 10 seconds.
6. Install the HVAC/ECAS fuse.
7. Start the vehicle.
8. Wait 40 seconds for the HVAC control module to self-calibrate.
9. Verify that no DTCs have set as current DTCs.

HVAC Control Module

The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal. The control module supports the following features

Auxiliary HVAC Control Module

Auxiliary HVAC Control functions are integrated into the Rear Seat Entertainment Module. The Rear Seat Entertainment Module communicates Rear HVAC settings over serial data. The control switches enable the module to send a GMLAN serial data message to the from auxiliary HVAC control module to the HVAC Control Module for the change request. The Auxiliary HVAC Control module does not store auxiliary HVAC DTCs.

Auxiliary HVAC Control Functions

All Auxiliary functions and DTCs are handled by the HVAC Control Module. There are two ways the rear functions can be controlled.

Control from the HVAC Control Module: If the AUX button on the HVAC Control Module is pressed, the auxiliary HVAC system will be enabled. The settings for the auxiliary will mimic the driver settings on the HVAC control module.

Control from the Auxiliary HVAC Control Module: If at any time any of the three auxiliary controls are adjusted, control of the rear HVAC system will transfer to the auxiliary controls. If the Aux button is not currently enabled, adjusting the auxiliary controls will enable it, even if the front system is OFF.

Mode Actuator

The mode 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 5 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 0-5 volts.

The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, 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.

Auxiliary Mode Actuator

The auxiliary mode 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 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts.

The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, 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 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 linear pulse modulated signal to the blower motor control processor over 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.

Auxiliary Blower Motor Control Processor

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

Air Speed - Front Control

The blower control switch is integrated into the HVAC control module. The two rocker type switches provide the vehicle operator the ability to select several blower speeds. The HVAC control module uses a bar graph type display to indicate the selected blower speed. The HVAC control module provides a linear pulse modulated (LPM) signal to the blower motor through the blower motor speed control circuit. The blower motor changes speed based on the received LPM signal from the HVAC control module. Power and ground are provided to the blower motor through the battery positive voltage and ground circuits. When the HVAC control module is operating in AUTO mode, the system automatically controls the blower speed. Power and ground are provided to the HVAC control module by the ignition 3 voltage and the ground circuits.

Air Speed - Auxiliary

A rocker type switch on the RSA control module provides the operator the ability to select several blower speeds. The RSA control module uses a bar graph to indicate the selected blower speed. The auxiliary blower motor control processor supplies a 5-volt reference to the auxiliary HVAC control module on the auxiliary blower motor speed control circuit. The auxiliary HVAC control module pulls the 5-volt reference low towards ground to provide a blower motor speed signal. As the voltage decreases the blower speed increases. Power and ground are provided to the auxiliary blower motor control processor through the battery positive voltage and ground circuits. The auxiliary HVAC control module can not request A/C operation from the powertrain control module (PCM).

Air Distribution

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

1. Defrost
2. Defog
3. Panel
4. BI-Level
5. Floor

The mode actuator is connected to the mode door by a cam type linkage system. Depending on the position of the door, air is directed through the HVAC module and distributed through various ducts leading to the outlets in the dash. If the HVAC control module detects a fault with the mode door the HVAC control module will try to drive the actuator for a predetermined amount of time, to defrost, which is the defaulted position for the mode door actuator. When the mode switch is placed in the defrost or defog positions the A/C is commanded ON and the recirculation door is moved to the outside air position to help reduce window fogging. A/C is available in all modes and recirculation is only available in the panel and bi-level modes.

Front Defrost

When defrost is selected, the A/C compressor is activated. The A/C compressor clutch will engage when ambient temperatures are above 3°C (38°F). The blower motor will be activated, regardless of the coolant temperature. The HVAC control module will override the auxiliary HVAC control module so a high volume of air is delivered to the front defrost vents. The rear window defogger does not affect the HVAC system.

Air Distribution - Auxiliary Control

The auxiliary HVAC system provides ventilation for the rear seat occupants. The rear seat occupants will exercise control of the auxiliary air delivery modes, air speed and air temperature setting.

When the auxiliary mode switch is toggled, a signal is sent to the auxiliary mode actuator through the auxiliary mode door control circuit. Power and ground are supplied to the auxiliary mode actuator through the ignition 3 voltage and ground circuits.

A rocker type switch on the RSA control module provides the operator the ability to select several blower speeds. The RSA control module uses a bar graph to indicate the selected blower speed.

The HVAC control module is a class 2 device that interfaces between the vehicle operator and the HVAC System to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal. The control module supports the following features

The auxiliary HVAC control module is a GMLAN device that receives analog inputs from the front HVAC control assembly and GMLAN message inputs from the rear seat audio control module to maintain auxiliary air temperature and auxiliary air distribution settings. The battery positive voltage circuit provides power that the control module uses for KAM. If the battery positive voltage circuit loses power, all auxiliary HVAC DTCs and settings will be erased from KAM. The auxiliary HVAC control module will perform a recalibration of the electric actuators when commanded with a scan tool or if KAM is lost. This will ensure the actuators are moving with in the calibrated range.

Air Temperature Actuator

The air temperature actuators are 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 5 volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts.

The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, 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.

Auxiliary Air Temperature Actuator

The auxiliary 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 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, 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.

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. Inside air temperature sensor assembly
3. Upper left air temperature sensor
4. Upper right air temperature sensor
5. Lower left air temperature sensor
6. Lower right 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 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.

If the HVAC control module detects a malfunctioning sensor, then the control module software will use a defaulted air temperature value. The default value for the ambient and inside air temperature sensors will be displayed on the scan tool. The default value for the duct air temperature sensors will not be displayed on the scan tool. The scan tool parameter for the duct air temperature sensors are the actual state of the signal circuit. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.

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 PCM converts the voltage signal to a pressure value.

The A/C refrigerant pressure sensor protects the A/C system from operating when an excessively high pressure condition exists. The PCM disables the compressor clutch if the A/C pressure is more than 2957 kPa (429 psi). The clutch will be enabled after the pressure decreases to less than 1578 kPa (229 psi).

A/C Low Pressure Switch

The A/C low pressure switch protects the A/C System from a low pressure condition that could damage the A/C compressor or cause evaporator icing. The HVAC control module applies 5 volts to the A/C low pressure switch signal circuit. The switch will open when the A/C low side pressure reaches 138-172 kPa (20-25 psi) as measured at the switch/accumulator. This prevents the A/C compressor from operating. The switch will then close when A/C low pressure side reaches 275-317 kPa (40-46 psi) as measured at the switch/accumulator. This enables the A/C compressor to turn back ON.

The low pressure switch uses refrigerant pressure to open and close a set of electrical contacts. When A/C request is authorized the switch is closed and shows normal status. During this state the switch will show 0 volts on the A/C low pressure sensor signal circuit. When A/C request is denied due to a low pressure condition the switch will be open. During this state the switch will show 5 volts on the A/C low pressure sensor signal circuit.