HVAC Systems - Automatic Cadillac Escalade GMT800

Fastener Tightening Specifications

HVAC Systems - Automatic Fastener Tightening Specifications

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Test Description

The numbers below refer to the step numbers on the diagnostic table.

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1. 3. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 5. Determine if the Rear Seat Audio (RSA) Control Module, HVAC Control Module, Body Control Module or Powertrain Control Module have set DTCs which may affect HVAC operation are present.
3. 6. The presence of DTCs which begin with "U", except U1500, indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed. Be sure to diagnose all other "U" codes before diagnosing a U1500.
4. 7. Answer Yes if the first three characters of the DTC name begins with B10; regardless of the last two characters.

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Scan Tool Data Definitions

A/C High Side Pressure: The scan tool displays 0-3450 kPa (0-500 psi). The voltage applied to the PCM input from the A/C refrigerant pressure sensor is converted to a pressure value.

A/C High Side Pressure: The scan tool displays 0-5 volts. The voltage applied to the PCM input for the A/C refrigerant pressure sensor.

A/C Relay Command: The scan tool displays On/Off. The scan tool displays the control decision for the compressor clutch relay output as determined by the PCM.

A/C Request Signal: The scan tool displays Yes/No. The scan tool displays Yes when the PCM receives a class 2 message from the HVAC control module to engage the A/C compressor clutch. The scan tool displays No when the PCM receives a class 2 message from the HVAC control module to disengage the A/C compressor clutch.

A/C Switch: The scan tool displays On/Off. The scan tool displays On when the A/C request switch is active. The scan tool displays Off when the A/C request switch is inactive.

AC Permission: The scan tool displays Withheld/Granted. The scan tool displays Granted when the HVAC control module determines that conditions for compressor clutch engagement are present. The scan tool displays Withheld when the HVAC control module determines that conditions for compressor clutch engagement are not present.

Air Inlet Door Actual: The scan tool displays 0-255 counts. The voltage applied to the recirculation door position input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Air Inlet Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Air Mix Door Left Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired left air temperature door position as determined by the HVAC control module.

Air Mix Door Right Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired right air temperature door position as determined by the HVAC control module.

Air Temp. Switch Pos.: The scan tool displays a numeric value between 0-18. The lower the numeric value the lower the temperature that is selected. The numeric value is a reading of the voltage signal applied to the input of the front auxiliary temperature switch to the auxiliary HVAC control module

Ambient Air Temp. Sensor: The scan tool displays -40 to +215°C (-40 to +419°F). The current value of the ambient air temperature display on the HVAC control module.

Auto Switch: The scan tool displays On/Off. The scan tool displays On when the automatic switch is active. The scan tool displays Off when the automatic switch is inactive.

Aux. Temp Dr. Motor Command: The scan tool displays 0-255 counts. The scan tool displays the desired auxiliary air temperature door position as determined by the auxiliary HVAC control module.

Aux. Temp Dr. Motor Status: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the auxiliary HVAC control module.

Aux. Temp Dr. Position: The scan tool displays 0-255 counts. The voltage applied to the auxiliary air temperature door position input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Battery Voltage: The scan tool displays 0-25 volts. The voltage measured from the battery positive voltage circuit and the ground circuit of the HVAC control module.

Blower Motor PWM Speed: The scan tool displays 0-114%. The scan tool displays the control decision for the blower motor speed as determined by the HVAC control module. The scan tool displays 114% when the blower motor is commanded to maximum speed. The scan tool displays 0% when the blower motor is commanded OFF.

Blower Switch Pos.: The scan tool displays a numeric value between 0-15. Position 0 is the AUTO position. Position 1 is the AUX. position. Position 2 turns off the auxiliary controls. Positions 3-15 are the auxiliary blower motor speed positions. The lower the number the lower the auxiliary blower motor speed input. The numeric value is a reading of the voltage signal applied to the input of the front auxiliary blower motor switch to the auxiliary HVAC control module.

ECT Sensor: The scan tool displays -39 to +140°C (-38 to +284°F). The voltage applied to the PCM input from the engine coolant temperature sensor is converted to a temperature value.

ECT Sensor: The scan tool displays 0-5 volts. The voltage applied to the PCM input for the engine coolant temperature sensor.

Engine Coolant Temp: The scan tool displays -39 to +140°C (-38 to +284°F). The scan tool displays the engine coolant temperature as detected by the PCM.

Fan Down Button: The scan tool displays On/Off. The scan tool displays On when the fan down switch is active. The scan tool displays Off when the fan down switch is inactive.

Fan Up Button: The scan tool displays On/Off. The scan tool displays On when the fan up switch is active. The scan tool displays Off when the fan up switch is inactive.

Front Defrost Switch: The scan tool displays On/Off. The scan tool displays On when the defrost switch is active. The scan tool displays Off when the defrost switch is inactive.

IGN. Since Current DTC: The scan tool displays 0-100. The number of the ignition cycles since the setting of the most recent current diagnostic trouble code (DTC).

Inside Air Temp. Fan: The scan tool displays On/Off. The scan tool displays the control decision for the fan motor output as determined by the HVAC control module. The fan motor is internal to the inside air temperature sensor assembly.

Inside Air Temp.: The scan tool displays -40 to +215°C (-40 to +419°F). The voltage applied to the HVAC control module input for the inside air temperature sensor is converted to a temperature value.

Inside Air Temp. Fan: The scan tool displays On/Off. The scan tool displays the control decision for the fan motor output as determined by the auxiliary HVAC control module. The fan motor is internal to the auxiliary inside air temperature sensor assembly.

Inside Air Temp. Sensor: The scan tool displays 0-255 counts. The voltage applied to the auxiliary inside air temperature input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Left Mix Door Actual: The scan tool displays 0-255 counts. The voltage applied to the left air temperature door position input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Left Mix Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Left Solar Sensor: The scan tool displays 0-255 counts. The voltage applied to the left sunload input of the BCM is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Left Temp. Setting: The scan tool displays 15-32°C (60-90°F). The scan tool displays the selected temperature from the left air temperature switch.

LH AC Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the left upper duct air temperature input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

LH AC Duct Desired: The scan tool displays 0-255 counts. The desired value of the left upper duct air temperature input. The HVAC control module monitors the actual value of the duct air temperature input and accordingly positions the left air temperature door to achieve the desired duct air temperature.

LH Heater Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the left lower duct air temperature input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

LH Heater Duct Desired: The scan tool displays 0-255 counts. The desired value of the left lower duct air temperature input. The HVAC control module monitors the actual value of the duct air temperature input and accordingly positions the left air temperature door to achieve the desired duct air temperature.

Lower Heater Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the auxiliary lower air temperature sensor input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Mode Door Actual: The scan tool displays 0-255 counts. The voltage applied to the auxiliary mode door position input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Mode Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the auxiliary HVAC control module.

Mode Dr. Motor Command: The scan tool displays 0-255 counts. The scan tool displays the desired auxiliary mode door position as determined by the auxiliary HVAC control module.

Mode Select Position: The scan tool displays Off, Auto, Defrost, Heater, Htr/Def, Bi-Level, Panel. The scan tool displays the state of mode operation.

Mode Switch: The scan tool displays On/Off. The scan tool displays On when the mode switch is active. The scan tool displays Off when the mode switch is inactive.

Mode Switch Pos.: The scan tool displays a numeric value between 0-17. Position 0 is the Auto position. Position 1 is the Panel position. Position 9 is the Bi-Level position. Position 17 is the Floor position. The numeric value is a reading of the voltage signal applied to the input of the front auxiliary mode switch to the auxiliary HVAC control module

Off Switch: The scan tool displays On/Off. The scan tool displays On when the Off switch is active. The scan tool displays Off when the Off switch is inactive.

Outside Air Temp. Filtered: The scan tool displays -40 to +215°C (-40 to +419°F). The current value of the ambient air temperature display on the HVAC control module.

Outside Air Temp. Raw: The scan tool displays -40 to +215°C (-40 to +419°F). The voltage applied to the HVAC control module input from the ambient air temperature sensor is converted to an unfiltered temperature value.

Pressure Cycle Switch: The scan tool displays Low Pressure/Normal. The current state of the input from the A/C low pressure switch. The scan tool displays Low Pressure when the switch is open and displays Normal when the switch is closed. The low pressure switch opens when low side pressure decreases to approximately 151 kPa (22 psi) and closes when the low side pressure increases to approximately 275 kPa (40 psi).

Rear HVAC Fan Down Sw.: The scan tool displays Active/Inactive. The scan tool displays Active when the fan down switch is active. The scan tool displays Inactive when the fan down switch is inactive.

Rear HVAC Fan Select Pos.: The scan tool displays Auto/Off/Low/Med/High. The scan tool displays the state of fan operation.

Rear HVAC Fan Speed: The scan tool displays Auto/Off/Low/Med/High. The scan tool displays the state of fan operation.

Rear HVAC Fan Up Switch: The scan tool displays Active/Inactive. The scan tool displays Active when the fan up switch is active. The scan tool displays Inactive when the fan up switch is inactive.

Rear HVAC Mode Select Pos.: The scan tool displays Auto/Floor/Bi-Level/ Panel. The scan tool displays the state of mode operation.

Rear HVAC Mode Switch: The scan tool displays Active/Inactive. The scan tool displays Active when the mode switch is active. The scan tool displays Inactive when the mode switch is inactive.

Recirculate Switch: The scan tool displays On/Off. The scan tool displays On when the recirculation switch is active. The scan tool displays Off when the recirculation switch is inactive.

RH AC Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the right upper duct air temperature input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

RH AC Duct Desired: The scan tool displays 0-255 counts. The desired value of the right upper duct air temperature input. The HVAC control module monitors the actual value of the duct air temperature input and accordingly positions the right air temperature door to achieve the desired duct air temperature.

RH Heater Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the right lower duct air temperature input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

RH Heater Duct Desired: The scan tool displays 0-255 counts. The desired value of the right lower duct air temperature input. The HVAC control module monitors the actual value of the duct air temperature input and accordingly positions the right air temperature door to achieve the desired duct air temperature.

Right Mix Door Actual: The scan tool displays 0-255 counts. The voltage applied to the right air temperature door position input of the HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Right Mix Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Right Solar Sensor: The scan tool displays 0-255 counts. The voltage applied to the BCM input from the right sunload sensor is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

Right Temp. Setting: The scan tool displays 15 to 32°C (60 to 90°F). The scan tool displays the selected temperature from the right air temperature switch.

Upper Htr. Duct Actual: The scan tool displays 0-255 counts. The voltage applied to the auxiliary upper air temperature sensor input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 counts is approximately equal to 1 V.

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Circuit Description

The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air surrounding the front of the vehicle. The module applies 5 volts to internal input resistor that is connected to the signal circuit of the air temperature sensor. The module provides ground to the air temperature sensor through the low reference circuit. The HVAC control module monitors the voltage drop across the air temperature sensor and uses the input for automatic control calculations. When the air temperature is cold, the resistance of the sensor is high and the voltage signal is high. When the air temperature is hot, the resistances of the sensor is low and the voltage signal is low. The HVAC control module also uses the ambient air temperature input to calculate the value of the ambient air temperature display.

Conditions for Running the DTC

1. Battery voltage to the HVAC control module is greater than 8.7 V and less than 16.5 V.
2. The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module determines that the voltage applied to the input for the air temperature sensor is less than 0.09 V or greater than 4.9 V.

Action Taken When the DTC Sets

The HVAC control module uses a default value of 10°C (50°F) for the ambient air temperature display. The scan tool also displays 10°C (50°F) as the value for the Outside Air Temp. Raw parameter. This value will be displayed on the scan tool.

Conditions for Clearing the DTC

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

The number below refers to the step number on the diagnostic table.

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1. 2. Verifies that the condition that set the DTC is present.

The inside air temperature sensor assembly allows the HVAC control module to monitor the temperature of the air inside the passenger compartment. The module applies 5 volts to internal input resistor that is connected to the signal circuit of the air temperature sensor. The module provides ground to the air temperature sensor through the low reference circuit. The HVAC control module monitors the voltage drop across the air temperature sensor and uses the input for automatic control calculations. When the air temperature is cold, the resistance of the sensor is high and the voltage signal is high. When the air temperature is hot, the resistances of the sensor is low and the voltage signal is low.

1. Battery voltage to the HVAC control module is greater than 8.7 V and less than 16.5 V.
2. The ignition is turned ON.

The HVAC control module determines that the voltage applied to the input for the air temperature sensor is less than 0.09 V or greater than 4.9 V.

The HVAC control module use a default value of 25°C (77°F) for the Inside Air Temp, parameter. This value will be displayed on the scan tool.

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

The number below refers to the step number on the diagnostic table.

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1. 2. Verifies that the condition that set the DTC is present.

The auxiliary inside air temperature sensor assembly allows the auxiliary HVAC control module to monitor the temperature of the air inside the passenger compartment. The module applies 5 volts to internal input resistor that is connected to the signal circuit of the air temperature sensor. The module provides ground to the air temperature sensor through the low reference circuit. The auxiliary HVAC control module monitors the voltage drop across the air temperature sensor and uses the input for automatic control calculations. When the air temperature is cold, the resistance of the sensor is high and the voltage signal is high. When the air temperature is hot, the resistances of the sensor is low and the voltage signal is low.

1. Battery voltage to the auxiliary HVAC control module is greater than 8.7 V and less than 16.5 V.
2. The ignition is turned ON.

The auxiliary HVAC control module determines that the voltage applied to the input for the auxiliary inside air temperature sensor is less than 0.09 V or greater than 4.9 V.

The auxiliary HVAC control module use a default value of 128 Counts for the Inside Air Temp. Sensor parameter. This value will not be displayed on the scan tool. The value displayed on the scan tool is the actual value of the signal circuit.

1. The DTC will become history if the auxiliary HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

The numbers below refers to the step numbers on the diagnostic table.

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1. 2. Verifies that the temperature displayed is not within the calibrated range.
2. 3. Tests for the proper operation of the circuit in the high voltage range.
3. 4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

The following DTCs are for the air temperature sensors located in the discharge air ducts

1. B0174 is for the upper left air temperature sensor.
2. B0179 is for the lower left air temperature sensor.
3. B0510 is for the upper right air temperature sensor.
4. B0515 is for the lower right air temperature sensor.

Air temperature sensors allow the HVAC control module to monitor the temperature of the discharge air in the HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts.

1. Battery voltage is within 8.7-16.5 V.
2. The ignition is ON.

The HVAC control module determines that the value of the air temperature parameter is less than 5 counts or greater than 250 counts.

The HVAC control module uses a default air temperature value for further automatic control calculations. The default values are not displayed on the scan tool.

1. The DTC will become history if the HVAC control module no longer detects a fault.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

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1. 2. Verifies that the temperature displayed is not within the calibrated range.
2. 3. Tests for the proper operation of the circuit in the high voltage range.
3. 4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

The following DTCs are for the left and right sunload sensors.

1. B0183 is for the left sunload sensor.
2. B0188 is for the right sunload sensor.

The left and right sunload sensors provide the HVAC control module with inputs as to the amount heat load the sun is placing on the interior of the vehicle. The sunload sensors are photodiodes that are sensitive to light intensity. The Body Control Module (BCM) applies 5 volts to internal input resistors that are connected to the left and right signal circuits of the sunload sensor assembly. The BCM provides ground to the sensors through the low reference circuit. The BCM monitors the voltage drops across the sunload sensors and converts the voltage values to count values where 1 V is approximately equal to 51 counts. As the light intensity increases, the sunload sensors allow more current to travel through the circuits and the signal voltages decrease. As the light intensity decreases, the sunload sensors allow less current to travel through the circuits and the signal voltages increase. The BCM transmits the data to the HVAC control module over the class 2 serial data circuit.

The ignition is ON.

The BCM determines that the value of the sunload sensor signal is less than 5 counts or greater than 250 counts.

The action taken will be for the BCM to revert to a calibrated default value.

1. The DTC will become history if the BCM no longer detects a failure.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

The numbers below refer to the step numbers on the diagnostic table.

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1. 2. Verifies that the value displayed is within the specified range.
2. 3. Tests for the proper operation of the circuit in the high voltage range.
3. 4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

The following DTCs are for the HVAC door actuators

1. B0229 is for the recirculation actuator.
2. B0414 is for the left air temperature actuator.
3. B0424 is for the right air temperature actuator.
4. B3770 is for the mode actuator.

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The module supplies a 5-volt source voltage to the potentiometer on the 5-volt reference circuit. The module supplies ground to the potentiometer through the low reference circuit. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The module converts the voltage value to a count value where 1-volt is approximately equal to 51 counts.

The HVAC control module calibrates the travel range of the HVAC door actuators when it is initially powered by the battery positive voltage circuit. During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position. The door actuators can be calibrated again with a scan tool.

1. Battery voltage is 8.7-16.5 volts.
2. The ignition is ON.

The DTC sets when one of the following conditions are present

1. The actual door position value for the actuator is less than 5 counts.
2. The actual door position value for the actuator is greater than 250 counts.
3. The actuator fails calibration because the calculated travel range value is too great or too small.

1. If the DTC sets because the actual door position value is out of range, the HVAC control module will command the actuator to a default position.
2. If the DTC sets because the actuator failed a calibration, the HVAC control module will attempt to calibrate the motor in the next transition from OFF to RUN mode.

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

Diagnostic Aids

1. If the condition is not present Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions: A misaligned actuator Broken linkages or binding linkages A broken door or a binding door An obstruction that prevents the door from operating within the full range of motion Missing seals to the door Poor connections at the harness connector of the door actuator
3. If a signal circuit of an actuator is short to ground and the resistance across the internal potentiometer is low, then this condition could cause a multiple DTC concern.

The numbers below refer to the step numbers on the diagnostic table.

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1. 3. At least two of the DTCs must be set as current DTC to ensure correct diagnosis. If only one DTC is present then the answer is No.
2. 5. Tests for the proper operation of the circuit in the low voltage range.
3. 6. Tests for the proper operation of the circuit in the high voltage range. If the jumper fuse opens when you perform this test, the circuit is shorted to ground.
4. 7. Tests for a short to voltage in the 5-volt reference circuit.
5. 8. Tests for a high resistance or for an open in the low reference circuit.
6. 9. This step tests for an open on the low reference circuit that is common to all of the actuators. Choose the easiest HVAC door actuator that set a DTC to start the diagnosis.
7. 10. Disconnecting each actuator, one at a time, isolates the disconnected actuators signal circuit from the 5-volt reference circuit that is common to all the actuators.

The following DTCs are for the HVAC door actuators

1. B0263 is for the mode actuator.
2. B0268 is for the recirculation actuator.
3. B0408 is for the left air temperature actuator.
4. B0418 is for the right air temperature actuator.

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit inside the actuators receives control signals from the HVAC control module and controls the internal stepper motor. When a door positional change is required, the HVAC control module calculates a commanded door position. The module compares the commanded door position to the actual door position and determines the needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an input to the internal logic circuit of the door actuator. A 5-volt signal increases the door position. A 0-volt signal decreases the door position. When the commanded door position is equal to the actual door position, the HVAC control module sends a 2.5-volt signal to the door actuator and motor rotation stops. The ignition 3-voltage circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit through the low reference circuit.

1. Source voltage is 8.7-16.5 volts.
2. The ignition is ON.
3. The HVAC control module commands the actuator to move.

The actual door position is not near the commanded door position.

The HVAC control module does not command the actuator to move for the remainder of the ignition cycle.

1. The DTC becomes history during the next ignition cycle in which the HVAC control module no longer detects a stall condition.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. If the condition is not present Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. Inspect the appropriate door and door actuator for the following conditions: A misaligned door actuator Binding linkages A binding door An obstruction that prevents the door actuator from operating within the full range of motion

The numbers below refer to the step numbers on the diagnostic table.

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1. 2. Determines if the HVAC door actuator is stalled.
2. 3. Applies control circuit voltage to the input of the HVAC door actuator.

The following DTCs are for the HVAC door actuators

1. B0429 is for the auxiliary air temperature actuator.
2. B3531 is for the auxiliary mode actuator.

The auxiliary HVAC control module controls the auxiliary HVAC door actuators to regulate the airflow through the auxiliary HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit inside the actuators receives control signals from the auxiliary HVAC control module and controls the internal stepper motor. When a door positional change is required, the auxiliary HVAC control module calculates a commanded door position. The module compares the commanded door position to the actual door position and determines the needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an input to the internal logic circuit of the door actuator. A 5 volt signal increases the door position. A 0 volt signal decreases the door position. When the commanded door position is equal to the actual door position, the auxiliary HVAC control module sends a 2.5 volt signal to the door actuator and motor rotation stops. The ignition 3 voltage circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit through the low reference circuit.

1. Source voltage is 8.7-16.5 volts.
2. The ignition is ON.
3. The auxiliary HVAC control module commands the actuator to move.

The actual door position is not near the commanded door position.

The auxiliary HVAC control module does not command the actuator to move for the remainder of the ignition cycle.

1. The DTC becomes history during the next ignition cycle in which the auxiliary HVAC control module no longer detects a stall condition.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. If the condition is not present Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. Inspect the appropriate door and door actuator for the following conditions: A misaligned door actuator A binding door An obstruction that prevents the door actuator from operating within the full range of motion

The numbers below refer to the step numbers on the diagnostic table.

Scheme 85

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1. 2. Determines if the auxiliary HVAC door actuator is stalled.
2. 3. Applies control circuit voltages to the input of the auxiliary HVAC door actuator.

The following DTCs are for the auxiliary HVAC door actuators

1. DTC B0434 is for the auxiliary air temperature actuator.
2. DTC B3764 is for the auxiliary mode actuator.

The auxiliary HVAC control module controls the auxiliary HVAC door actuators to regulate the airflow through the auxiliary HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The module supplies a 5-volt source voltage to the potentiometer on the 5-volt reference circuit. The module supplies ground to the potentiometer through the low reference circuit. The auxiliary HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The module converts the voltage value to a count value where 1 volt is approximately equal to 51 counts. The auxiliary HVAC control module calibrates the travel range of the auxiliary HVAC door actuators when it is initially powered by the battery positive voltage circuit. During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position. The door actuators can be calibrated again with a scan tool.

1. Battery voltage is 8.7-16.5 volts.
2. The ignition is ON.

The DTC sets when one of the following conditions are present

1. The actual door position value for the actuator is less than 5 counts.
2. The actual door position value for the actuator is greater than 250 counts.
3. The actuator fails calibration because the calculated travel range value is too great or too small.

1. If the DTC sets because the actual door position value is out of range, the auxiliary HVAC control module will command the actuator to a default position.
2. If the DTC sets because the actuator failed a calibration, the auxiliary HVAC control module will attempt to calibrate the motor in the next transition from OFF to RUN mode.

1. The DTC will become history if the auxiliary HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

1. If the condition is not present Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions: A misaligned actuator A broken door or a binding door An obstruction that prevents the door from operating within the full range of motion Missing seals to the door Poor connections at the harness connector of the door actuator

The numbers below refer to the step numbers on the diagnostic table.

Scheme 87

Scheme 88

Scheme 89

1. 2. Ensure to observe the correct parameter for each DTC. Aux. Temp Dr. Position is for the auxiliary air temperature actuator. Mode Door Actual is for the auxiliary mode actuator.
2. 4. Tests for the proper operation of the circuit in the low voltage range.
3. 5. Tests for the proper operation of the circuit in the high voltage range. If the jumper fuse opens when you perform this test, the circuit is shorted to ground.
4. 6. Tests for a short to voltage in the 5-volt reference circuit.
5. 7. Tests for a high resistance or for an open in the low reference circuit.
6. 13. The voltage will vary between 0-5 volts during normal operation. Ensure to observe the actuator driveshaft and the volt meter when jumping the control circuit with 5-volt reference and the ground circuits. The actuator and the auxiliary HVAC control module connectors must be connected during this step.

The ignition 3 voltage circuit is a discrete input to the HVAC control module. The HVAC control modules uses the input to determine that the ignition switch is in the RUN position. When the ignition switch is in the RUN position, ignition voltage is applied to the input.

1. Source voltage is 8.7-16.5 volts.
2. The HVAC control module receives a RUN power mode message from the BCM over the class 2 serial data circuit.

The HVAC control module does not detect ignition voltage on the ignition 3 voltage input.

The HVAC control module will continue to operate using the class 2 power mode messaging.

Scheme 90

1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
2. The history DTC will clear after 100 fault free ignition cycles.
3. The DTC can be cleared with a scan tool.

The following DTCs are for the auxiliary air temperature sensors located in the auxiliary HVAC ducts

1. B3579 is for the upper auxiliary air temperature sensor.
2. B3584 is for the lower auxiliary air temperature sensor.

The auxiliary air temperature sensors allow the auxiliary HVAC control module to monitor the temperature of the discharge air in the auxiliary HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The auxiliary HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The auxiliary HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts.

1. Battery voltage is within 8.7-16.5 V.
2. The ignition is ON.

The auxiliary HVAC control module determines that the value of the air temperature parameter is less than 5 counts or greater than 250 counts.

The auxiliary HVAC control module uses a default air temperature value for further automatic control calculations. The default values are displayed on the scan tool. The default value is 50 Counts.

1. The DTC will become history if the auxiliary HVAC control module no longer detects a fault.
2. The history DTC will clear after 100 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

The number below refers to the step number on the diagnostic table.

Scheme 91

1. 2. Verifies that the condition that set the DTC is present.

The powertrain control module (PCM) monitors the high side refrigerant pressure via a A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low the signal voltage is low. When pressure is too high the PCM will not allow the A/C compressor clutch to engage.

The PCM detects an A/C request.

1. The A/C refrigerant pressure sensor signal is less than 0.1 volts for 5 seconds.
2. The A/C refrigerant pressure sensor signal is greater than 4.9 volts for 5 seconds.

The malfunction indicator lamp (MIL) will not illuminate.

1. The DTC will become history if the PCM no longer detects a failure.
2. The history DTC will clear after 40 fault-free ignition cycles.
3. The DTC can be cleared with a scan tool.

For an intermittent, Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 92

Scheme 93

Scheme 94

1. 3. Tests for the proper operation of the circuit in the low voltage range.
2. 4. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
3. 5. Tests for a short to voltage in the 5-volt reference circuit.
4. 6. Tests for a high resistance or an open in the low reference circuit.

Important: The following steps must be completed before using the symptom tables.

1. Perform the «DIAGNOSTIC SYSTEM CHECK - HVAC SYSTEMS - AUTOMATIC»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control module(s) can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following information: «AIR DELIVERY DESCRIPTION AND OPERATION»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic__air-delivery-description-and-operation) «AIR TEMPERATURE DESCRIPTION AND OPERATION»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic__air-temperature-description-and-operation)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to CHECKING AFTERMARKET ACCESSORIES in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures. Refer to «AIR TEMPERATURE DESCRIPTION AND OPERATION»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic__air-temperature-description-and-operation) .
6. The following conditions may cause window fogging: Wet carpet or mats High humidity Interior water leak Blocked A/C evaporator drain tube Maximum passenger capacity Blocked body pressure relief valves
7. Inspect the air distribution system for causes of reduced air flow: Obstructed or dirty passenger compartment air filter, if equipped Blocked or damaged air inlet or outlet vents

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «HVAC COMPRESSOR CLUTCH DOES NOT ENGAGE»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
2. «HVAC COMPRESSOR CLUTCH DOES NOT DISENGAGE»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
3. «BLOWER MOTOR ALWAYS ON»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
4. Blower Motor Inoperative, See «Blower Motor Inoperative»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
5. «BLOWER MOTOR MALFUNCTION»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
6. «BLOWER MOTOR ALWAYS ON - AUXILIARY»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
7. «BLOWER MOTOR INOPERATIVE - AUXILIARY»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
8. «BLOWER MOTOR MALFUNCTION - AUXILIARY»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
9. «TOO HOT IN VEHICLE»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
10. «TOO COLD IN VEHICLE»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
11. «TOO HOT IN VEHICLE - AUXILIARY»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
12. «TOO COLD IN VEHICLE - AUXILIARY»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
13. «AIR DELIVERY IMPROPER»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
14. «AIR RECIRCULATION MALFUNCTION»(/cadillac/escalade/gmt800-2001-2006/remont/automatic-hvac-system/#hvac-systems-automatic)
15. LEAK TESTING in Heating, Ventilation and Air Conditioning
16. NOISE DIAGNOSIS - BLOWER MOTOR in Heating, Ventilation and Air Conditioning
17. NOISE DIAGNOSIS - AIR CONDITIONING (A/C) SYSTEM in Heating, Ventilation and Air Conditioning
18. NOISE DIAGNOSIS - HVAC MODULE in Heating, Ventilation and Air Conditioning
19. ODOR DIAGNOSIS in Heating, Ventilation and Air Conditioning

A/C compressor clutch will not engage under the following conditions

1. The A/C high side line pressure is over 2957 kPa (429 psi).
2. The A/C low side line pressure is under 151 kPa (22 psi).
3. Throttle angle is at 100 percent.
4. Engine speed is more than 5500 RPM.
5. Engine coolant temperature (ECT) is more than 121°C (250°F).
6. Ambient air temperature is less than 5°C (40°F).

The numbers below refer to the step numbers on the diagnostic table.

Scheme 95

Scheme 96

Scheme 97

Scheme 98

Scheme 99

1. 2. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.
2. 3. This step ensures that the HVAC control module is receiving an input from the A/C switch.
3. 4. These actions will enable the A/C compressor to operate.
4. 5. This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.
5. 7. The A/C low pressure switch parameter is out of range when the HVAC control module interprets the signal being below 151 kPa (22 psi).
6. 8. This action will simulate a closed switch condition. If the Pressure Cycle Switch parameter reads Low Pressure then there is a circuit condition or a condition with the HVAC control module.
7. 11. The A/C compressor relay output from the powertrain control module (PCM) is disabled if the A/C high side system pressure is interpreted to be higher than 2958 kPa (429 psi).

The number below refers to the step number on the diagnostic table.

Scheme 100

Scheme 101

1. 2. These actions will disable the HVAC control module output to powertrain control module (PCM).

The number below refers to the step number on the diagnostic table.

Scheme 102

1. 4. The blower motor parameter must be commanded ON before an OFF command will function.

Scheme 103

Scheme 104

Scheme 105

Scheme 106

1. 2. This step verifies that the HVAC control module Fan Up Switch parameter matches the requested state of the blower motor switch.
2. 3. This step verifies that the HVAC control module Fan Down Switch parameter matches the requested state of the blower motor switch.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 107

Scheme 108

Scheme 109

1. 2. This step tests for auxiliary blower motor operation in the OFF setting.
2. 3. The Blower Motor Test parameter must be commanded ON before an OFF command will function.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 110

Scheme 111

Scheme 112

Scheme 113

1. 8. This step verifies that the auxiliary HVAC control module is commanding the auxiliary blower motor to operate at HI speed to reflect the requested speed of the front auxiliary HVAC control assembly. The scan tool should display a value greater than 50 percent.
2. 11. This step tests for an internal fault of the RSA control module, or the auxiliary HVAC control module. If the Rear HVAC Fan Speed parameter changes as the fan switch speed changes then replace the auxiliary HVAC control module. If the Rear HVAC Fan Speed parameter does not change replace the RSA control module.
3. 12. This step verifies that the front auxiliary HVAC control assembly receives a 5 V reference and ground from the auxiliary HVAC control module. If all 3 parameters are at 0 when the auxiliary fan HIGH speed is requested then proceed to step 13.
4. 15. This step verifies that the auxiliary HVAC control module is commanding the auxiliary blower motor to operate at HI speed to reflect the requested speed of the front auxiliary HVAC control assembly. If the Blower Switch Pos. parameter is 15 and the auxiliary blower motor is not on HIGH then replace the auxiliary HVAC control module.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 114

Scheme 115

Scheme 116

1. 1. Ensure to perform the HVAC diagnostic system check. If DTCs B0434, DTC B3764 and the auxiliary blower motor is always on, then the 5 volt reference circuit of the auxiliary HVAC door actuators is pulled low to ground. The DTC diagnostic must be performed to ensure circuit is tested.
2. 5. This step tests for an internal failure of the rear seat audio (RSA) control module, or the auxiliary HVAC control module.
3. 6. This step tests the 5 volt reference supplied by the auxiliary blower motor control processor.
4. 7. This step tests for an internal failure of the front auxiliary HVAC control assembly.

1. The condition may be intermittent. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. The air temperature actuators can be calibrated. Refer to RE-CALIBRATING ACTUATORS .

The numbers below refer to the step numbers on the diagnostic table.

Scheme 117

Scheme 118

Scheme 119

Scheme 120

Scheme 121

Scheme 122

1. 6. The ambient air temperature must be above 5°C (40°F) in order for this A/C compressor test to be run.
2. 8. This step ensures that the lower air temperature sensors operate properly. The LH and RH Heater Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
3. 9. This step ensures that the upper air temperature sensors operate properly. The LH and RH AC Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
4. 11. This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.
5. 14. Use the following table to determine that the recorded scan tool values are within range for the recorded probe temperatures of the J 43600.

1. The condition may be intermittent. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. The air temperature actuators can be calibrated. Refer to RE-CALIBRATING ACTUATORS .

The number below refers to the step number in the diagnostic table.

Scheme 123

Scheme 124

Scheme 125

Scheme 126

Scheme 127

Scheme 128

1. 8. This step ensures that the lower air temperature sensors operate properly. The LH and RH Heater Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
2. 9. This step ensures that the upper air temperature sensors operate properly. The LH and RH AC Duct Actual parameter count values should lower as the air temperature of the ducts get warmer. If there is a high resistance in either of the air temperature sensors circuits or the sensor itself then the count value of the effected sensor would remain high.
3. 11. This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.
4. 15. Use the following table to determine that the recorded scan tool values are within range for the recorded probe temperatures.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 129

Scheme 130

Scheme 131

Scheme 132

Scheme 133

1. 2. This step ensures that the primary HVAC system is functioning properly.
2. 3. The DTCs listed could set if a calibration of the actuators is performed.
3. 6. If the condition does not occur when a A/C request has been made then you must bypass the A/C compressor and cooling system diagnostic information.
4. 9. This step ensures that the front auxiliary control assembly is providing an auxiliary air temperature input to the auxiliary HVAC control module.
5. 10. This step ensures that the rear seat audio control is providing an auxiliary air temperature input to the auxiliary HVAC control module.
6. 12. When taking a temperature reading allow for a 3°C (5°F) temperature variance.
7. 15. When the front auxiliary HVAC control assembly is disconnected, and there is no fault on auxiliary air temperature switch control circuit, the scan tool will read a high count value for the Air Temp. Switch Pos. parameter. A short to ground on circuit will have low count value.

The numbers below refer to the step numbers on the diagnostic table.

Scheme 134

Scheme 135

Scheme 136

Scheme 137

Scheme 138

1. 2. This step ensures that the primary HVAC system is functioning properly.
2. 3. The DTCs listed could set if a calibration of the actuators is performed.
3. 6. If the condition does not occur when a heating request has been made then you must bypass the A/C compressor and cooling system diagnostic information.
4. 9. This step ensures that the front auxiliary control assembly is providing an auxiliary air temperature input to the auxiliary HVAC control module.
5. 10. This step ensures that the rear seat audio control is providing an auxiliary air temperature input to the auxiliary HVAC control module.
6. 12. When taking temperature reading allow for a 3°C (5°F) temperature variance.
7. 15. When the front auxiliary HVAC control assembly is disconnected, and there is no fault on auxiliary air temperature switch control circuit, the scan tool will read a high count value for the Air Temp. Switch Pos. parameter. A short to ground on circuit will have low count value.

Scheme 139

1. The condition may be intermittent. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. Inspect the air delivery system for the following conditions: A dirty HVAC air filter, if applicable An obstruction to the airflow Air leaks Misaligned air ducts Broken or binding linkages or doors

The number(s) below refer to the step number(s) on the diagnostic table.

Scheme 140

Scheme 141

1. 3. This step tests for auxiliary blower motor that does not operate from the front auxiliary HVAC control assembly regardless of the desired blower motor speed.
2. 4. This step tests for a auxiliary blower motor that operates, yet does not accurately respond to the desired blower motor speed from the front auxiliary HVAC control assembly.
3. 5. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s) from the front auxiliary HVAC control module.
4. 6. This step tests for an inoperative auxiliary mode actuator in one mode position(s) or in the wrong mode position(s) from the console HVAC control module.

Scheme 142

Re-Calibrating Actuators

When replacing the HVAC control module it will be necessary to allow the HVAC control module to perform a re-calibration process. When installing the HVAC control module be sure to perform the following

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is calibrating. If interrupted improper HVAC performance will result.

1. Place the ignition switch to the OFF position.
2. Disconnect the scan tool.
3. Install the HVAC control module.
4. Re-connect all previously disconnected components.
5. Start the vehicle.
6. Wait 40 seconds for the HVAC control module to re-calibrate.
7. Verify that no DTCs have set as current DTCs.

When replacing the motor assembly it will be necessary to allow the HVAC control module to perform a re-calibration process. When installing the motor assembly be sure to perform one of the following

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is calibrating. If interrupted improper HVAC performance will result.

Preferred Method (w/ Scan Tool)

1. Clear all DTCs
2. Place the ignition switch in the OFF position.
3. Install the motor assembly.
4. Re-connect all previously disconnected components.
5. Start the vehicle.
6. With the scan tool, initiate the Motor Re-calibration feature of the HVAC module Special Functions menu.
7. Verify that no DTCs have set as current DTCs.

Important: Do not adjust any controls on the HVAC control module while the HVAC control module is calibrating. If interrupted improper HVAC performance will result.

Alternate Method (w/o Scan Tool)

1. Clear all DTCs
2. Place the ignition switch to the OFF position.
3. Disconnect the scan tool.
4. Install the motor assembly.
5. Re-connect all previously disconnected components.
6. Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
7. Re-install the HVAC/ECAS fuse.
8. Start the vehicle.
9. Wait 40 seconds for the HVAC control module to re-calibrate.
10. Verify that no DTCs have set as current DTCs.

Scheme 143

1. Remove the instrument panel accessory trim plate. Refer to BEZEL REPLACEMENT - INSTRUMENT PANEL (I/P) CLUSTER in Instrument Panel, Gages and Console.
2. Remove the accessory switch from the instrument panel. Refer to ACCESSORY SWITCH REPLACEMENT in Instrument Panel, Gages and Console.
3. Remove the screws from the HVAC control module.
4. Depress the control assembly retaining tabs and remove the HVAC control module from the instrument panel.
5. Disconnect the electrical connectors from the HVAC control module.

Installation Procedure

Important: The key should be in the off position when connecting the electrical connectors to ensure proper calibration.

Scheme 144

1. Connect the electrical connectors to the HVAC control module.
2. Install the HVAC control module into the instrument panel. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
3. Install the screws to the HVAC control module. Tighten Tighten the screws to 1.9 N.m (17 lb in).
4. Install the accessory switch to the instrument panel. Refer to ACCESSORY SWITCH REPLACEMENT in Instrument Panel, Gages and Console.
5. Install the instrument panel accessory trim plate. Refer to BEZEL REPLACEMENT - INSTRUMENT PANEL (I/P) CLUSTER in Instrument Panel, Gages and Console. Important: Do not adjust any controls on the HVAC control module while the HVAC control module is calibrating. If interrupted improper HVAC performance will result.
6. Start the vehicle and let run for one minute.

Scheme 145

1. Remove the console roof screw.
2. Remove the console (1) from the headliner.
3. Disconnect the electrical connectors (3) from the console (1).
4. Remove the console (1) from the vehicle.
5. Remove the HVAC control assembly (2) from the console (1) by depressing the 4 tabs on the back of the HVAC control assembly (2).

Scheme 146

1. Install the HVAC control assembly (2) to the console (1).
2. Connect the electrical connectors (3) to the console (1).
3. Install the console (1) to the headliner. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
4. Install the overhead console screw. Tighten Tighten the screw to 2 N.m (18 lb in).

Scheme 147

1. Remove the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connectors (3,4) from the auxiliary HVAC control module (1).
3. Remove the screws from the auxiliary HVAC control module (1).
4. Remove the auxiliary HVAC control module (1) from the auxiliary HVAC module (2).

Scheme 148

1. Install the auxiliary HVAC control module (1) to the auxiliary HVAC module (2). NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the screws to the auxiliary HVAC control module (1). Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connectors (3,4) to the auxiliary HVAC control module (1).
4. Install the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 149

Scheme 150

1. If equipped, remove the sound insulator panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages and Console.
2. Disconnect the electrical connector at the blower motor.
3. Disconnect the electrical connector (4) from the blower motor control processor (2).
4. Remove the blower motor control processor retaining screws (3) from the HVAC module (1).
5. Remove the blower motor control processor (2) from the HVAC module (1).

Scheme 151

Scheme 152

1. Install the blower motor control processor (2) to the HVAC module (1). NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the blower motor control processor retaining screws. Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector (4) to the blower motor control processor (2).
4. Connect the electrical connector at the blower motor.
5. If equipped, install the sound insulator panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages and Console.

Scheme 153

1. Remove the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the auxiliary blower motor processor (1).
3. Remove the retaining screws from the auxiliary blower motor processor (1).
4. Remove the auxiliary blower motor processor (1) from the auxiliary HVAC module (2).

Scheme 154

1. Install the auxiliary blower motor processor (1) to the auxiliary HVAC module (2). NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the retaining screws to the auxiliary blower motor processor (1). Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector to the auxiliary blower motor processor (1).
4. Install the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 155

Scheme 156

1. Remove the air distribution duct. Refer to AIR DISTRIBUTOR DUCT REPLACEMENT in Heating, Ventilation and Air Conditioning.
2. Disconnect the electrical connection from the recirculation actuator (1).
3. Remove the recirculation actuator retaining screws.
4. Remove the recirculation actuator.

Scheme 157

Scheme 158

1. Install the recirculation actuator. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the recirculation actuator retaining screws. Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector to the recirculation actuator (1).
4. Install the air distribution duct. Refer to AIR DISTRIBUTOR DUCT REPLACEMENT in Heating, Ventilation and Air Conditioning.

Scheme 159

Scheme 160

Scheme 161

1. Remove the floor air outlet duct extension (1) from the floor duct (2).
2. Remove the Body Control Module. Refer to BODY CONTROL MODULE REPLACEMENT in Body Control System.
3. Disconnect the electrical connection at the mode actuator (10).
4. Remove the mode actuator mounting screws from the HVAC module.
5. Remove the mode actuator as an assembly with the actuator cam.

Scheme 162

Scheme 163

Scheme 164

1. Install the mode actuator as an assembly with the actuator cam. Line up the heater/defroster lever with the mode actuator cam slot. Line up the A/C lever with the mode actuator cam. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the mode actuator mounting screws to the HVAC module. Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connection at the mode actuator (10).
4. Install the Body Control Module. Refer to BODY CONTROL MODULE REPLACEMENT in Body Control System.
5. Install the floor air outlet duct extension (1) to the floor air duct (2).

Scheme 165

Scheme 166

Scheme 167

1. Remove the floor air outlet duct extension (1) from the floor duct (2).
2. Remove the center console. Refer to CONSOLE REPLACEMENT (WITH CONSOLE MOUNTING BRACKET) or CONSOLE REPLACEMENT (W/O CONSOLE MOUNTING BRACKET) in Instrument Panel, Gages and Console.
3. Remove the screws from the center console duct.
4. Remove the center console duct.
5. Disconnect the electrical connection from the mode actuator (10).
6. Remove the mode actuator mounting screws from the HVAC module.
7. Remove the mode actuator as an assembly with the actuator cam.

Scheme 168

Scheme 169

Scheme 170

1. Install the mode actuator as an assembly with the actuator cam. Line up the heater/defroster valve lever with the mode actuator cam slot. Line up the A/C valve lever with the mode actuator cam. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the mode actuator mounting screws to the HVAC module. Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connection at the mode actuator (10).
4. Install the center console duct.
5. Install the screws to the center console duct. Tighten Tighten the screws to 1.6 N.m (14 lb in).
6. Install the center console. Refer to CONSOLE REPLACEMENT (WITH CONSOLE MOUNTING BRACKET) or CONSOLE REPLACEMENT (W/O CONSOLE MOUNTING BRACKET) in Instrument Panel, Gages and Console.
7. Install the floor air outlet duct extension (1) to the floor air duct (2).

Scheme 171

1. Remove the I/P carrier. Refer to INSTRUMENT PANEL (I/P) CARRIER REPLACEMENT in Instrument Panel, Gages and Console.
2. Disconnect the electrical connector (4) from the right air temperature actuator (3).
3. Remove the screws from the right air temperature actuator (3).
4. Remove the right air temperature actuator (3) from the HVAC module assembly (2).

Scheme 172

1. Install the right air temperature actuator (3) from the HVAC module assembly (2). NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the screws to the right air temperature actuator (3). Tighten Tighten the screws to 2 N.m (18 lb in).
3. Connect the electrical connector to the right air temperature actuator.
4. Install the I/P carrier. Refer to INSTRUMENT PANEL (I/P) CARRIER REPLACEMENT in Instrument Panel, Gages, and Console.
5. Reprogram the air temperature actuator. Refer to RE-CALIBRATING ACTUATORS .

Scheme 173

1. Remove the I/P insulator panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages and Console.
2. Disconnect the electrical connector (1) from the left air temperature actuator (2).
3. Remove the screws from the left air temperature actuator (2).
4. Remove the left air temperature actuator (2) from the HVAC module assembly (3).

Scheme 174

1. Install the left air temperature actuator (2) to the HVAC module assembly (3). NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the screws to the left air temperature actuator (2). Tighten Tighten the screws to 2 N.m (18 lb ft).
3. Install the electrical connector (1) to the left air temperature actuator (2).
4. Install the I/P insulator panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages and Console.
5. Reprogram the left air temperature actuator. Refer to RE-CALIBRATING ACTUATORS .

Scheme 175

1. Remove the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the auxiliary air temperature actuator.
3. Remove the retaining screws from the auxiliary air temperature actuator.
4. Remove the auxiliary air temperature actuator (1) from the rear auxiliary HVAC module.

Scheme 176

1. Install the auxiliary air temperature actuator (1) to the auxiliary HVAC module. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the auxiliary air temperature actuator retaining screws. Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector to the auxiliary air temperature actuator.
4. Install the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 177

1. Remove the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the mode actuator (1).
3. Remove the retaining screws from the mode actuator.
4. Remove the mode actuator (1) from the vehicle.

Scheme 178

1. Install the mode actuator (1) to the vehicle. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the screws to the mode actuator (1). Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector to the mode actuator.
4. Install the left rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 179

1. Remove the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the mode actuator (1).
3. Remove the retaining screws from the mode actuator.
4. Remove the mode actuator (1) from the vehicle.

Scheme 180

1. Install the mode actuator (1) to the vehicle. NOTE: Refer to «FASTENER NOTICE»(/cadillac/escalade/gmt800-2001-2006/remont/oem-general-information/#gm-vehicles-cautions-notices__fastener-notice) in Cautions and Notices.
2. Install the screws to the mode actuator (1). Tighten Tighten the screws to 1.6 N.m (14 lb in).
3. Connect the electrical connector to the mode actuator.
4. Install the right rear quarter trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 181

1. Remove the right side C-pillar trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the rear upper A/C temperature sensor (11).
3. Remove the rear upper A/C temperature sensor (11) from the air distribution duct.

Scheme 182

1. Install the rear upper A/C temperature sensor (11) to the air distribution duct.
2. Connect the electrical connector to the rear upper A/C temperature sensor (11).
3. Install the right side C-pillar trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 183

1. Remove the I/P upper trim panel. Refer to TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER in Instrument Panel, Gages, and Console.
2. Disconnect the electrical connector (1) from the upper right air temperature sensor (2).
3. Remove the upper right air temperature sensor (1) from the air distributor duct (3).

Scheme 184

1. Install the upper right air temperature sensor (1) to the air distributor duct (3).
2. Connect the electrical connector (1) from the upper right air temperature sensor (2).
3. Install the I/P upper trim panel. Refer to TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER in Instrument Panel, Gages, and Console.

Scheme 185

1. Remove the upper left air temperature sensor (2) from the air distributor duct (1).
2. Disconnect the electrical connector (3) from the upper left air temperature sensor (2).

Scheme 186

1. Install the upper left air temperature sensor (2) to the air distributor duct (1).
2. Connect the electrical connector (3) to the upper left air temperature sensor (2).

Scheme 187

1. Remove the right side C-pillar trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.
2. Disconnect the electrical connector from the auxiliary lower A/C temperature sensor (10).
3. Remove the auxiliary lower A/C temperature sensor (10) from the air distribution duct.

Scheme 188

1. Install the rear lower A/C temperature sensor (10) to the air distribution duct.
2. Connect the electrical connector to the rear lower A/C temperature sensor (10).
3. Install the right side C-pillar trim panel. Refer to TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (UTILITY) or TRIM PANEL REPLACEMENT - REAR QUARTER - RIGHT (SUBURBAN) in Interior Trim.

Scheme 189

1. Disconnect the electrical connector from the lower left air temperature sensor (1).
2. Remove the lower left air temperature sensor (1) from the HVAC module (2).

Scheme 190

1. Install the lower left air temperature sensor (1) to the HVAC module (2).
2. Connect the electrical connector to the lower left air temperature sensor (1).

Scheme 191

1. Remove the I/P lower closeout panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages, and Console.
2. Remove the right floor duct. Refer to AIR OUTLET DUCT REPLACEMENT - FLOOR, RH in Heating, Ventilation and Air Conditioning.
3. Remove the center console. Refer to CONSOLE REPLACEMENT (WITH CONSOLE MOUNTING BRACKET) or CONSOLE REPLACEMENT (W/O CONSOLE MOUNTING BRACKET) in Instrument Panel, Gages, and Console.
4. Disconnect the electrical connector from the lower right air temperature sensor (1).
5. Remove the lower right air temperature sensor (1).

Scheme 192

1. Install the lower right air temperature sensor (1).
2. Connect the electrical connector to the lower right air temperature sensor (1).
3. Install the center console. Refer to CONSOLE REPLACEMENT (WITH CONSOLE MOUNTING BRACKET) or CONSOLE REPLACEMENT (W/O CONSOLE MOUNTING BRACKET) in Instrument Panel, Gages, and Console.
4. Install the right floor duct. Refer to AIR OUTLET DUCT REPLACEMENT - FLOOR, RH in Heating, Ventilation and Air Conditioning.
5. Install the I/P lower closeout panel. Refer to INSULATOR REPLACEMENT - INSTRUMENT PANEL (I/P) in Instrument Panel, Gages, and Console.

Scheme 193

1. Remove the radiator grille from the vehicle. Refer to GRILLE REPLACEMENT (CADILLAC) or GRILLE REPLACEMENT (AVALANCHE) in Exterior Trim.
2. Remove the push pin retainer from the sensor mounted on the radiator support brace.
3. Disconnect the electrical connector from the sensor.

Scheme 194

1. Connect the electrical connector to the sensor.
2. Install the sensor to the radiator support brace and install the push pin retainer.
3. Install the radiator grille to the vehicle. Refer to GRILLE REPLACEMENT (CADILLAC) or GRILLE REPLACEMENT (AVALANCHE) in Exterior Trim.

Scheme 195

Scheme 196

1. Remove the left windshield garnish molding. Refer to GARNISH MOLDING REPLACEMENT - WINDSHIELD PILLAR in Interior Trim.
2. Remove the left center pillar assist handle. Refer to ASSIST HANDLE REPLACEMENT - REAR in Interior Trim.
3. Remove the left center pillar garnish molding. Refer to GARNISH MOLDING REPLACEMENT - CENTER PILLAR in Interior Trim.
4. Remove the left sunshade. Refer to SUNSHADE REPLACEMENT in Interior Trim.
5. Gently pull down the headliner.
6. Disconnect the electrical connector from the inside air temperature sensor.
7. Partially remove the inside air temperature sensor from the headliner.
8. Remove the sensor grille from the inside air temperature sensor.
9. Remove the inside air temperature sensor from the headliner.

Scheme 197

Scheme 198

1. Install the new sensor grille to the headliner.
2. Install the inside air temperature sensor to the headliner and sensor grille.
3. Connect the electrical connector to the inside air temperature sensor.
4. Install the left sunshade. Refer to GARNISH MOLDING REPLACEMENT - CENTER PILLAR in Interior Trim.
5. Install the left center pillar garnish molding. Refer to GARNISH MOLDING REPLACEMENT - CENTER PILLAR in Interior Trim.
6. Install the left center assist handle. Refer to ASSIST HANDLE REPLACEMENT - REAR in Interior Trim.
7. Install the left windshield garnish molding. Refer to GARNISH MOLDING REPLACEMENT - WINDSHIELD PILLAR in Interior Trim.

Scheme 199

Scheme 200

1. Remove the third pillar molding. Refer to TRIM REPLACEMENT - THIRD PILLAR (TAHOE / YUKON / ESCALADE / SUBURBAN) or TRIM REPLACEMENT - THIRD PILLAR (AVALANCHE / ESCALADE EXT) in Interior Trim.
2. Remove the left rear coat hook, if equipped. Refer to COAT HOOK REPLACEMENT in Interior Trim.
3. Remove the rear headliner retainers from the front headliner.
4. Carefully lower the headliner from the roof Velcro retainers.
5. Disconnect the electrical connector from the inside air temperature sensor.
6. Partially remove the auxiliary inside air temperature sensor from the headliner.
7. Remove the sensor grille from the auxiliary inside air temperature sensor.
8. Remove the auxiliary inside air temperature sensor from the headliner.

Scheme 201

Scheme 202

1. Install the new sensor grille to the headliner.
2. Install the inside air temperature sensor to the headliner and sensor grille.
3. Connect the electrical connector to the inside air temperature sensor.
4. Secure the headliner to the roof Velcro.
5. Install the rear headliner retainers to the front headliner.
6. Install the left rear coat hook, if equipped. Refer to COAT HOOK REPLACEMENT in Interior Trim.
7. Install the third pillar molding. Refer to TRIM REPLACEMENT - THIRD PILLAR (TAHOE / YUKON / ESCALADE / SUBURBAN) or TRIM REPLACEMENT - THIRD PILLAR (AVALANCHE / ESCALADE EXT) in Interior Trim.

Scheme 203

1. Remove the instrument panel upper trim panel. Refer to TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER in Instrument Panel, Gages and Console.
2. Remove the sun load sensor (2) from the upper trim panel.
3. Disconnect the electrical connector.

Scheme 204

1. Connect the electrical connector.
2. Install the sun load sensor (2) to the upper trim panel.
3. Install the instrument panel upper trim panel. Refer to TRIM PANEL REPLACEMENT - INSTRUMENT PANEL (I/P) UPPER in Instrument Panel, Gages and Console.

Air Delivery Description and Operation

The air delivery description and operation is divided into 7 areas

1. HVAC Control Components
2. Air Speed
3. Auxiliary Air Speed
4. Air Delivery
5. Auxiliary Air Delivery
6. Recirculation Operation
7. Automatic Operation

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

Scheme 205

Auxiliary HVAC Control Module

The auxiliary HVAC control module is a class 2 device that receives analog inputs from the front HVAC control assembly and class 2 message inputs from the rear seat audio (RSA) 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 keep alive memory (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.

RSA Control Module

The RSA Control Module is a class 2 device that interfaces between the rear seat passengers and the auxiliary HVAC control module. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). Air temperature, blower motor and air delivery rocker type switches are located on the face of the module. These switches enable the module to send a class 2 serial data message to the auxiliary HVAC control module for the change request. The module does not store auxiliary HVAC DTCs.

Front Auxiliary HVAC Control Assembly

The front auxiliary HVAC control assembly is a non-class 2 device that interfaces between the front seat occupants and the auxiliary HVAC control module. A 5-volt reference is supplied to the control assembly by the auxiliary HVAC control module. The control assembly varies the 5-volt reference through three integrated potentiometers to control mode, air temperature door position, and blower motor speed inputs to the auxiliary HVAC control module.

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 potentiometer's 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.

Blower Motor Control Processor

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 low side pulse width 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 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 increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the auxiliary HVAC control module 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 2 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 blower motor control processor supplies a 5 V reference to the HVAC control module on the blower motor speed control circuit. The HVAC control module pulls the 5 V 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 blower motor control processor 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.

Air Speed - Auxiliary

There are 2 separate operator controls for the auxiliary HVAC system. There is the front auxiliary HVAC control assembly and the RSA control module. If the front auxiliary blower motor switch is in the AUX. position, then the system will only function with inputs to the front auxiliary HVAC control assembly. If the front auxiliary blower motor switch is in the OFF position, then the RSA control module does not respond to input. The auxiliary HVAC control module can not request A/C operation from the PCM. 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 V reference to the auxiliary HVAC control module on the auxiliary blower motor speed control circuit. The auxiliary HVAC control module pulls the 5 V 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.

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.

The mode actuator is an electronic stepper motor with feedback potentiometers. The HVAC control module sends signals to the mode door actuator through the mode door control circuit. Zero volts drive the actuator in one direction while 5-volts move the actuator in the opposite direction. When the actuator receives 2.5-volts, the actuator rotation stops. A 5-volt reference signal is sent out over the 5-volt reference circuit to the mode actuator. When you select a desired mode setting, logic determines the value of the mode actuator signals. The HVAC control module's software uses this reference voltage in order to determine the position of the mode actuator through the mode door position signal circuit. The motor moves the mode door to the desired position.

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.

When the HVAC control module is ON, the air that is delivered to the auxiliary HVAC system is the low auxiliary blower speed. When the operator selects medium blower speed, power is delivered to the auxiliary blower motor through the auxiliary blower motor medium speed control circuit. When the operator selects high blower speed, power is delivered to the auxiliary blower motor through the auxiliary blower motor high speed control circuit. Ground is provided to the blower motor through the ground circuit. Power and ground are provided to the auxiliary HVAC control module through the ignition 3 voltage and ground circuits.

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. Including the OFF position. 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. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost or defog positions. 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. If the HVAC control module detects a fault with the recirculation door the HVAC control module will try to drive the actuator for a predetermined amount of time, to outside air, which is the defaulted position for the recirculation actuator.

Automatic Operation

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in Automatic mode, the following is required

1. The Auto switch must be activated
2. The air temperature switch must be in any other position other than full hot or full cold position

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Monitor the following sensors: Inside air temperature sensor Ambient Air Temperature Sensor Lower Left Air Temperature Sensor Lower Right Air Temperature Sensor Upper Left Air Temperature Sensor Upper Right Air Temperature Sensor
2. Regulate blower motor speed
3. Position the air temperature actuator
4. Position the mode actuator
5. Position the recirculation actuator
6. Request A/C operation

Air Temperature Description and Operation

The air temperature controls are divided into 7 areas

1. HVAC Control Components
2. Heating and A/C Operation
3. Auxiliary Heating and A/C Operation
4. Automatic Operation
5. Auxiliary Automatic Operation
6. Engine Coolant
7. A/C Cycle

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

Scheme 206

The auxiliary HVAC control module is a class 2 device that receives analog inputs from the front HVAC control assembly and class 2 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 keep alive memory (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.

Rear Seat Audio Control Module

The rear seat audio control module is a class 2 device that interfaces between the rear seat passengers and the auxiliary HVAC control module. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). Air temperature, blower motor and air delivery rocker type switches are located on the face of the module. Pressing a switch enables the module to send a class 2 serial data message to the auxiliary HVAC control module for the change request. The module does not store auxiliary HVAC DTCs.

The front auxiliary HVAC control assembly is a non-class 2 device that interfaces between the front seat occupants and the auxiliary HVAC control module. A 5 volt reference is supplied to the control assembly by the auxiliary HVAC control module. The control assembly varies the 5 volt reference through three integrated potentiometers to control auxiliary mode door position, auxiliary air temperature door position and auxiliary blower motor speed inputs to the auxiliary HVAC control module.

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. Inside Air Temperature Sensor Assembly-Auxiliary
4. Upper Left Air Temperature Sensor
5. Upper Right Air Temperature Sensor
6. Lower Left Air Temperature Sensor
7. Lower Right Air Temperature Sensor
8. Upper Air Temperature Sensor-Auxiliary
9. Lower Air Temperature Sensor-Auxiliary

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.

If the HVAC control module or auxiliary 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.

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.

The ambient air temperature value is updated under the following conditions

Scheme 207

The scan tool has the ability to update the displayed ambient air temperature. To update the ambient air temperature display on the HVAC control module, perform the following procedure

1. Turn ON the ignition.
2. Simultaneously press the MODE, FRONT DEFROST and REAR DEFROST switches.

Sunload Sensor Assembly

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly. Low reference and signal circuits enable the sensor to operate. As the light shining upon the sensor gets brighter, the sensor resistance increases. The sensor signal decreases as the resistance increases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts.

The sunload sensor provides the HVAC control module a measurement of the amount of light shining on the vehicle. 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.

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

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 151 kPa (22 psi). This prevents the A/C compressor from operating. The switch will then close when A/C low pressure side reaches 275 kPa (40 psi). This enables the A/C compressor to turn back ON.

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. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature switch. The vehicle passenger can offset the passenger temperature as much as 16.7°C (30°F). Regardless of the temperature setting, the following can effect the rate that the HVAC system can achieve the desired temperature

1. Recirculation actuator setting
2. Difference between inside and desired temperature
3. Difference between ambient and desired temperature
4. Blower motor speed setting
5. Mode setting
6. Auxiliary HVAC settings

The control module makes the following actions when automatic operation is not selected, and an air temperature setting is selected

1. When the air temperature switch is placed in the warmest position, the control module commands the air temperature door to divert maximum air past the heater core.
2. When the air temperature switch is placed in the coldest position, the control module commands the air temperature door to direct air to bypass the heater core.
3. When the air temperature switch is placed between the warmest and coldest positions, the control module monitors the following sensor inputs to determine the air temperature door position that diverts the appropriate amount of air past the heater core in order to achieve the desired temperature: Sunload Duct temperatures Ambient temperature Inside temperature

The A/C system can be engaged by either pressing the A/C switch or during automatic operation. The HVAC control module sends a class 2 message to the 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.

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

1. Ambient air temperature above 4°C (40°F)
2. A/C low pressure switch signal circuit is grounded
3. A/C refrigerant pressure sensor parameter is less than 2957 kPa (429 psi)
4. PCM receives an A/C request from the HVAC control module
5. Engine coolant temperature (ECT) is less than 121°C (250°F)
6. The engine rpm is more than 550 rpm
7. The throttle position is less than 100%

The HVAC control module monitors the A/C low pressure switch signal circuit. If the voltage signal on this circuit has no voltage drop the module will interpret this condition as a low pressure, disabling the A/C request. The A/C low pressure switch will open its internal contacts at 151 kPa (22 psi). Then close the contacts at 275 kPa (40 psi) to resume A/C operation. This switch assists in cycling the A/C compressor and prevents A/C compressor operation if system has a low refrigerant level.

The PCM monitors the A/C refrigerant pressure sensor signal circuit. The voltage signal on this circuit is proportional to the refrigerant pressure inside the A/C high side pressure line. As the pressure inside the line increases, so does the voltage signal. If the pressure is above 2957 kPa (429 psi), the A/C compressor output is disabled. When the pressure lowers to 1578 kPa (229 psi), the PCM enables the compressor to operate.

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

1. The A/C high side pressure
2. An A/C system load on the engine
3. An excessive A/C high side pressure
4. The heat load at the A/C condenser

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

1. Ambient air temperature is less than 4°C (40°F)
2. Throttle position is 100%
3. The A/C low pressure switch is open
4. A/C high side pressure is more than 2957 kPa (429 psi)
5. A/C low side pressure is less than 151 kPa (22 psi)
6. Engine coolant temperature (ECT) is more than 121°C (250°F)
7. Engine speed is more than 5500 rpm
8. Transmission shift
9. PCM detects excessive torque load
10. PCM detects insufficient idle quality
11. PCM detects a hard launch condition

Auxiliary Heating and A/C Operation

There are 2 separate controls for the auxiliary HVAC system. There is the front auxiliary HVAC control assembly and the rear seat audio control module. These 2 components provide passenger inputs to the auxiliary HVAC control module. The auxiliary HVAC control module, which is mounted on the auxiliary HVAC case, controls all functions of the auxiliary HVAC system. If the front auxiliary HVAC control assembly is in any other position than OFF or AUX, then the auxiliary HVAC control module will use inputs from the front auxiliary HVAC control assembly. If the system is in the AUX position then the auxiliary HVAC control module will use inputs from the rear seat audio control module. If the front auxiliary blower motor switch is in the OFF position, then the auxiliary HVAC control module does not respond to input. The auxiliary HVAC control module can not request A/C operation from the PCM.

Placing the auxiliary air temperature switch to the warmest position diverts most of the airflow through the heater core, which increases the outlet air temperature. Placing the auxiliary air temperature switch to the coolest position diverts most of the airflow around the heater core, which decreases the outlet air temperature.

In automatic operation, the HVAC control module will maintain the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation.

To place the HVAC system in Automatic mode, the following is required

1. The Auto switch must be activated
2. The air temperature switch must be in any other position other than full hot or full cold position

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators will automatically be adjusted to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

1. Monitor the following sensors: Inside Air Temperature Sensor Ambient Air Temperature Sensor Lower Left Air Temperature Sensor Lower Right Air Temperature Sensor Upper Left Air Temperature Sensor Upper Right Air Temperature Sensor
2. Regulate blower motor speed
3. Position the air temperature actuator
4. Position the mode actuator
5. Position the recirculation actuator
6. Request A/C operation

Auxiliary Automatic Operation

In automatic operation, the auxiliary HVAC control module will maintain the comfort level inside of the vehicle by controlling the auxiliary blower motor, the auxiliary air temperature actuator and the auxiliary mode actuator.

To place the auxiliary HVAC system in Automatic mode, the following is required

1. The auxiliary blower motor switch on the front HVAC control assembly must be in the Auto position.
2. The auxiliary mode switch on the front HVAC control assembly must be in the Auto position.
3. The auxiliary air temperature switch must be in any other position other than full hot or full cold position.

Once the desired temperature is reached, the auxiliary blower motor, auxiliary mode and auxiliary temperature actuator will automatically be adjusted to maintain the temperature selected. The auxiliary HVAC control module performs the following functions to maintain the desired air temperature

1. Monitor the following sensors: Inside Air Temperature Sensor-Auxiliary Upper Air Temperature Sensor-Auxiliary Lower Air Temperature Sensor-Auxiliary
2. Regulate auxiliary blower motor speed
3. Position the auxiliary air temperature actuator
4. Position the auxiliary mode actuator

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 semi-cooled 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 the moisture and heat from the ambient air. 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 semi-cooled 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 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 the moisture and heat from the ambient air. 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.

Scheme 208

See also:
• FASTENER NOTICE
• DIAGNOSTIC SYSTEM CHECK - HVAC SYSTEMS - AUTOMATIC
• AIR DELIVERY DESCRIPTION AND OPERATION
• AIR TEMPERATURE DESCRIPTION AND OPERATION