Buick Enclave manuals

Buick Enclave: Description and Operation

AIR DELIVERY DESCRIPTION AND OPERATION

The air delivery description and operation is divided into 4 areas:

HVAC Control Components

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain desired 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 HVAC control module provides blower, air delivery mode, air temperature settings and input signals to auxiliary HVAC control module. The HVAC system assembly receives power from battery input with ignition 3 voltage circuit as a backup.

The HVAC control module supports the following features:

Buick Enclave. HVAC - Manual

Auxiliary HVAC Control Module (without RSA)

The Auxiliary HVAC Control Module uses a set of three potentiometers to control rear fan speed, temperature and mode settings. The Auxiliary HVAC Control module has inputs for 5V and low Reference that is used by all three potentiometers. There are three signal circuits between each of the potentiometers and the HVAC Control Module.

Auxiliary HVAC Control Module (with RSA)

Auxiliary HVAC Control functions are integrated into the Rear Seat Entertainment Module. The Rear Seat Entertainment Module communicates Rear HVAC settings over serial data.

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 rear HVAC system will be enabled. The settings for the rear 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.

Front Mode Actuator

The mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Auxiliary Mode Actuator

The auxiliary mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer.

Low reference, 5-volt reference, position signal and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Air Speed

Front Blower Motor Control Processor

The front blower motor control processor is an interface between front HVAC control module and front blower motor. The front blower control processor regulates supply voltage and ground circuits to front blower motor.

The front HVAC control module provides a blower speed signal to the control processor in order to command the desired blower motor speed. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

The blower motor forces air to circulate within the vehicle's interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant, until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.

As the requested blower speed increases, the following conditions occur:

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.

The following conditions must be met for afterblow to operate:

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

Auxiliary Blower Motor Control Processor

The auxiliary blower motor control processor is an interface between the auxiliary HVAC control module and the rear blower motor. The auxiliary blower motor control processor monitors supply voltage and ground circuits to the rear blower motor. The auxiliary HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The auxiliary blower motor control processor uses the blower motor ground as a low side control to adjust the blower motor 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 or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant, until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.

As the requested blower speed increases, the following conditions occur:

As the requested blower speed decreases, the following conditions occur:

Air Delivery

Front Control

The HVAC control module controls the distribution of air by the use of recirculation and mode actuators. The modes that may be selected are:

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 a fault is detected within the mode door travel, the HVAC control module will drive the actuator to defrost, which is a default position for the mode door actuator. Turning the mode door position to either defrost or defog positions, the HVAC control module will move the recirculation actuator to outside air reducing window fogging. When defrost/defog is selected, the A/C compressor is activated. The A/C compressor clutch will engage when ambient temperatures are above 3ºC (38ºF). A/C is available in all modes.

Recirculation is only available in Panel and Bi-Level modes. The rear window defogger does not affect the HVAC system.

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 the air temperature setting. The HVAC control module will have the ability to override the auxiliary HVAC control module by placing it in any position other than auxiliary.

The auxiliary mode switch in the HVAC control module allows the driver to direct the air flow in the rear of the vehicle between the floor, headliner or a blend between the 2 options. Power is provided to both front and auxiliary HVAC control modules from I/P fuse block on the ignition 3 voltage circuit.

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle. Regardless of the blower motor switch position, recirculation is available only in the Panel and Bi-Level mode switch positions. The mode switch must be placed in either the Panel or Bi-Level position before the blower motor switch is placed in the OFF position.

When Defrost or Defog positions are selected outside air is circulated to the windshield to reduce fogging. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times.

Dual Zone Operation

The HVAC control module uses dual temperature button switches. The dual zone controls allows for maximum temperature offset between and comfort between the driver and passenger. It is possible to select maximum airflow over the evaporator core with one dual zone switch along with maximum airflow over the heater core with the other dual zone switch. Each air temperature actuator is independent from the other and the passenger side is not limited in it's range of temperature offset.

Remote Start

Remote Start Activation

The following describes the HVAC control head functionality upon receiving the remote start active serial data message and a power mode status is set to off/awake. During remote start on the manual HVAC system the blower motor, mode doors, temperature doors, recirc door and A/C request will be set to the current setting on the control panel when the vehicle was last turned off. The rear defrost will be activated and the heated seats will be disabled.

Remote Start De-activation

When the remote start is exited, GMLAN power mode equals run mode or remote start engine. In the case of manual settings, the displays will revert to the actual state of operation of the features, on the basis of their normal control algorithms.

AIR TEMPERATURE DESCRIPTION AND OPERATION

The air temperature controls are divided into 5 areas:

HVAC Control Components

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain desired 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 HVAC control module provides blower, air delivery mode, air temperature settings and input signals to auxiliary HVAC control module. The HVAC system assembly receives power from battery input with ignition 3 Voltage circuit as a backup.

The HVAC control module supports the following features:

Buick Enclave. HVAC - Manual

Auxiliary HVAC Control Module (without RSA)

The Auxiliary HVAC Control Module uses a set of three potentiometers to control rear fan speed, temperature and mode settings. The Auxiliary HVAC Control module has inputs for 5V and low Reference that is used by all three potentiometers. There are three signal circuits between each of the potentiometers and the HVAC Control Module.

Auxiliary HVAC Control Module (with RSA)

Auxiliary HVAC Control functions are integrated into the Rear Seat Entertainment Module. The Rear Seat Entertainment Module communicates Rear HVAC settings over serial data.

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 rear HVAC system will be enabled. The settings for the rear 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.

Front Temperature Actuators

The air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer.

Low reference, 5-volt reference, position signal and 2 control circuits enable the actuator to operate. The driver air temperature actuator is a reverse polarity motor. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Auxiliary Temperature Actuator

The auxiliary air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal and 2 control circuits enable the actuator to operate. The driver air temperature actuator is a reverse polarity motor. The control circuits use either a 0 or 12- volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. 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, one of the control circuits is grounded. 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 removes power and ground from the control circuits.

Ambient Air Temperature Sensor

The ambient air temperature sensor mounts underhood and can be affected by city traffic, by idling and by restarting a hot engine. Therefore, the HVAC control module filters the value of the ambient air temperature sensor for temperature display. If the ambient air temperature sensor drops below 2ºC (35ºF) the compressor clutch will be disabled until the ignition is OFF for more than 3 hours or an instant OAT update is performed no matter what the actual temperature is due to the filtered value being used by the HVAC control module. The ambient air temperature value is updated under the following conditions:

Buick Enclave. HVAC - Manual

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 3234 kPa. The clutch will be enabled after the pressure decreases to less than 1931 kPa.

Dual Zone Operation

The HVAC control module uses dual temperature button switches. The dual zone controls allows for maximum temperature offset between and comfort between the driver and passenger. It is possible to select maximum airflow over the evaporator core with one dual zone switch along with maximum airflow over the heater core with the other dual zone switch. Each air temperature actuator is independent from the other and the passenger side is not limited in it's range of temperature offset.

Heating and A/C Operation

The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. Regardless of the temperature setting, the following can affect the rate that the HVAC system can achieve the desired temperature:

The manual HVAC system is a dual temperature zone system. There are 2 separate air temperature levers.

Moving the air temperature levers to the upward position diverts most of the airflow through the heater core, which increases the outlet air temperature. Moving the air temperature levers to the most downward position diverts most of the airflow around the heater core, which decreases the outlet air temperature. The right air temperature actuator controls the duct air temperature flowing through the center console to the second row seating passengers. The air temperature offset can be as much as 16.7ºC (30ºF).

Pressing the A/C button enables the HVAC control module to request A/C compressor engagement and turn ON the A/C button LED. The HVAC control module sends a GMLAN message to the Powertrain Control Module (PCM) for A/C compressor engagement. The PCM will provide a ground for the A/C compressor relay enabling it to close its internal contacts to send battery voltage to the A/C compressor clutch coil. The A/C compressor diode will prevent a voltage spike, resulting from the collapse of the magnetic field of the coil, from entering the vehicle electrical system when the compressor is disengaged. Defrost and Defog mode selections will request A/C operation but not turn ON the A/C LED.

The following conditions must be met in order for the A/C compressor clutch to turn ON:

The sensor information is used by the PCM to determine the following:

The A/C compressor has an A/C compressor temperature switch. This switch protects the compressor from over heating. The switch interrupts power to the compressor clutch coil. When the compressor core temperature rises above 124ºC (255ºF) the switch opens, disabling the compressor clutch coil. When the temperature lowers to 120ºC (248ºF) the switch closes, enabling the compressor clutch coil. This switch is not a serviceable part, it is integral to the A/C compressor.

Once engaged, the compressor clutch will be disengaged for the following conditions:

Auxiliary Heating and A/C Operation

The auxiliary air temperature switch is a rotary knob switch. Turning the air temperature switch to the warmest position diverts most of the airflow through the heater core, which increases the outlet air temperature. Turning the air temperature switch to the coolest position diverts most of the airflow around the heater core, which decreases the outlet air temperature.

Engine Coolant

Engine coolant is the essential element of the heating system. The thermostat controls the normal engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation.

Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC 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 door controls the amount of heat delivered to the passenger compartment. The coolant exits the heater core through the return heater hose and 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 A/C refrigerant pressure sensor 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 tubing and aluminum cooling fins, which allows rapid heat transfer for the refrigerant. The semicooled liquid refrigerant exits the condenser and flows through the liquid line, to the orifice tube.

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

Refrigerant exiting the orifice tube 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 through the suction line and back to the compressor, in a vapor state and 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.

A/C Cycle with Auxiliary

The auxiliary A/C system operates from the vehicles primary A/C system. The front or primary A/C system must be ON to allow the rear A/C system to function.

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 system used on this vehicle is a non cycling system. Non cycling A/C systems use a high pressure switch to protect the A/C system from excessive pressure. The high pressure switch will OPEN the electrical signal, to the compressor clutch, in the event that the refrigerant pressure becomes excessive. After the high and low side of the A/C system pressure equalize, the high pressure switch will CLOSE. Closing the high pressure switch will complete the electrical circuit to the compressor clutch. The A/C system is also 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.

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.

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 semicooled liquid refrigerant exits the condenser and flows through the liquid line. The liquid line flow is split and the liquid refrigerant flows to both the front or primary A/C system and to the liquid line for the rear A/C system.

The liquid refrigerant, flowing to the rear A/C system, flows into the rear thermal expansion value (TXV). The rear TXV is located at the rear evaporator inlet. The TXV is the dividing point for the high and the low pressure sides of the rear A/C system. As the refrigerant passes through the TXV, the pressure on the refrigerant is lowered. Due to the pressure differential on the liquid refrigerant, the refrigerant will begin to boil at the expansion device. The TXV also meters the amount of liquid refrigerant that can flow into the evaporator.

Refrigerant exiting the TXV flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the rear A/C module and passes through the evaporator core. Warm and moist air will cause the liquid refrigerant boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator through the suction line and back to the primary A/C systems suction line. Refrigerant in the primary A/C system suction line flows back to the compressor, in a vapor state and completes 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 rear A/C module for passenger comfort. The heat and moisture removed from the rear passenger compartment will also change form or condense and is discharged from the rear A/C module as water.

SPECIAL TOOLS AND EQUIPMENT

SPECIAL TOOLS

Buick Enclave. HVAC - Manual

 

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