HVAC Systems - Automatic: Other Pontiac G6 I

Sensor Resistance Table

Sensor Resistance Table

Scheme 31

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

HVAC Connector End Views

A/C Compressor Clutch

Scheme 46

HVAC Connector End Views

A/C Refrigerant Pressure Sensor

Scheme 47

HVAC Connector End Views

Air Temperature Actuator

Scheme 48

HVAC Connector End Views

Air Temperature Sensor - Lower

Air Temperature Sensor - Upper

HVAC Connector End Views

Air Temperature Sensor - Upper

Scheme 49

HVAC Connector End Views

Ambient Air Temperature Sensor

Scheme 50

HVAC Connector End Views

Blower Motor

Scheme 51

HVAC Connector End Views

Blower Motor Control Module

Scheme 52

HVAC Connector End Views

HVAC Control Module C1

Scheme 53

HVAC Connector End Views

HVAC Control Module C2

Mode Actuator

HVAC Connector End Views

Mode Actuator

Recirculation Actuator

HVAC Connector End Views

Recirculation Actuator

Scheme 54

HVAC Connector End Views

Sunload Sensor

2A and 61

Sets after 2 occurrences of the test fail code setting conditions listed below in the same ignition cycle.

51 and 04

Sets after one occurrence of the test fail code setting conditions listed below in the same ignition cycle.

2A, 04, 51 and 61

The following failures occur and set the DTC

1. The HVAC control module does not detect any movement of the actuator.
2. The HVAC control module detects a measured actuator range that exceeds the calibratible value.
3. The HVAC control module detects a measured actuator range that is less than the calibratible value.
4. The HVAC control module detects a calibratible procedure time that exceeds the calibratible value.
5. The HVAC control module detects the actuator motor as stalled before the actuator motor reaches the expected stall at the end of the travel. When the drive voltage is reversed, the motor is unable to move more than a calibratible amount in the other direction.
6. The HVAC control module detects the actuator motor as stalled before the actuator motor reaches the expected stall at the end of the travel. But, when the drive voltage is reversed, the motor is able to move more than a calibratible amount in the other direction.

2A

The HVAC control module will use a default range to retry calibration procedure when the ignition is OFF.

61

The HVAC control module will stop trying to move the air temperature actuator motor during the current ignition cycle.

04

The HVAC control module will retry the command to move the actuator in a certain direction in 5-minute intervals.

51

The HVAC control module will retry calibration when the ignition is OFF.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

HVAC Compressor Clutch Does Not Disengage

HVAC Compressor Clutch Does Not Disengage

Blower Motor Always On

Blower Motor Always On

Blower Motor Inoperative

Blower Motor Inoperative

Blower Motor Malfunction

Blower Motor Malfunction

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 Special Functions.
6. Select HVAC.
7. Select ENTER to enable the afterblow.

When afterblow has been enabled by the scan tool the blower motor will operate at high speed for 4 minutes after the engine has been turned off.

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 operate for more than 2 minutes.
3. The engine must be turned off for at least 45 minutes.
4. The system voltage must be at least 12 volts.

Re-Calibrating Actuators

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.

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

Air Delivery Description and Operation

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

The after blow feature is a dealer turn on option. It is inactive in a new vehicle. The afterblow relay resides in the body control module (BCM). The BCM will directly turn on the hi blower fan relay to start the after blow process. The afterblow is a method where by the HVAC blower motor is run for a few minutes after the vehicle ignition is turned off in order to physically blow off excess condensation and eliminate odors associated with A/C usage.

The following conditions must be met for afterblow to operate

1. The A/C compressor operated for more than 10 seconds.
2. The A/C compressor, after operating for more than 10 seconds has not been deactivated for more than 10 minutes.
3. The system voltage is at least 11 volts to start and 10 volts to continue to run.
4. The ignition has been in the OFF position for at least 20 minutes.

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

1. The blower will run for 4 minutes at 59 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. If an outside temperature display concern occurs please refer to Outside Air Temperature Display Inaccurate or Inoperative .

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 Description and Operation

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.

Air Temperature Sensors

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 wake up 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.

Inside Air Temperature Sensor

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).

Engine Coolant

Engine coolant is the key element of the heating system. The engine thermostat controls the normal engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation. Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC module. The ambient air drawn through the HVAC module absorbs the heat of the coolant flowing through the heater core. The HVAC module distributes heated air to the passenger compartment for consistent passenger comfort. Opening or closing the HVAC module temperature door controls the amount of heat delivered to the passenger compartment. The coolant exits the heater core through the return heater hose and is recirculated back through the engine cooling system.

A/C Cycle

Refrigerant is the key element in an air conditioning system. R-134a is presently the only EPA approved refrigerant for automotive use. R-134a is an very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.

The A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the discharge hose and forced to flow to the condenser and then through the balance of the A/C system. The A/C system is mechanically protected with the use of a high pressure relief valve. If the high pressure switch were to fail or if the refrigerant system becomes restricted and refrigerant pressure continued to rise, the high pressure relief will pop open and release refrigerant from the system.

Compressed refrigerant enters the condenser in a high temperature, high pressure vapor state. As the refrigerant flows through the condenser, the heat of the refrigerant is transferred to the ambient air passing through the condenser. Cooling the refrigerant causes the refrigerant to condense and change from a vapor to a liquid state.

The condenser is located in front of the radiator for maximum heat transfer. The condenser is made of aluminum and aluminum cooling fins, which allows rapid heat transfer for the refrigerant. The semi-cooled liquid refrigerant exits the condenser and flows through the liquid line, to the thermal expansion valve.

The thermal expansion valve is located in the liquid line between the condenser and the evaporator. The thermal expansion valve is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the thermal expansion valve, the pressure of the refrigerant is lowered. Due to the pressure differential of the liquid refrigerant, the refrigerant will begin to vaporize at the thermal expansion valve. The thermal expansion valve also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the thermal expansion valve flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC module and passes through the evaporator core. Warm and moist air will cause the liquid refrigerant boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator back through the thermal expansion valve and into the suction line and back to the compressor, in a vapor state completing the A/C cycle of heat removal. At the compressor, the refrigerant is compressed again and the cycle of heat removal is repeated.

The conditioned air is distributed through the HVAC module for passenger comfort. The heat and moisture removed from the passenger compartment will also change form or condense and is discharged from the HVAC module as water under the vehicle.