Description And Operation; Automatic Hvac Description And Operation - GMC Chevy Colorado 2023 Manual

5-10 HVAC - Automatic

Description and Operation

Automatic HVAC Description and
Operation
The air temperature and the air delivery description and
operation are divided into the following:
HVAC Control Components
Air Speed and Blower Motor
Air Delivery
Heating and A/C Operation
Recirculation Operation
Automatic Operation
Engine Coolant and A/C System Refrigerant
HVAC Control Components
K9 Body Control Module
The body control module (BCM) is a CAN device that
interfaces between the operator and the HVAC system
to maintain and control desired air temperature and air
distribution settings. The BCM provides a device
ON-Signal for the HVAC controls. The BCM provides
blower, air delivery mode and air temperature control.
A26 Heater and Air Conditioning User Interface
Control - Front
The HVAC control contains all switches which are
required to control the functions of HVAC and serve as
interface between the operator and the BCM. The
selected values are passed to the BCM via serial data.
Actuators
Doors in the HVAC case assembly are used to control
air flow. The BCM operates the doors through the use
of actuators, with one actuator being used for each
door. The system has the following air control doors
and associated actuators: mode, left and right
temperature, and recirculation.
Each actuator used in the system is a LIN device
controlled by the BCM. The BCM supplies a 12 V
reference voltage to the actuators, and ground is
provided by the wiring harness. When the BCM sends a
request message to the actuator, the actuator then
operates internal stepper motors to move the door to
the required position.
Air Speed and M8 Blower Motor
The selected blower motor speed is passed from the
controls to the BCM via serial data.
The motor uses a fused B+, ground, control, and speed
output signal circuits to operate. The blower motor
speed is controlled by increasing or decreasing the
voltage drop on the ground side of the blower motor
speed control circuit. The BCM provides a low side
pulse width modulation (PWM) signal to the blower
motor to request a specific motor speed. The blower
motor internal circuitry translates the PWM signal and
drives the motor accordingly.
The blower motor has a signal wire used to output a
speed signal. The signal is monitored by the BCM. The
BCM monitors the blower motor speed to modify the
total commanded engine coolant flow rate, which is a
percentage of available coolant flow sent to the heater
core for occupant comfort and windshield defrosting.
The HVAC Blower Speed is monitored so that the ECM
can optimize engine coolant flow for fuel economy and
emissions.
Afterblow
Afterblow is a feature that dries the evaporator core by
operating the blower motor after the engine is turned
OFF under certain conditions. This reduces the amount
of microbial growth that can create undesirable odors.
For additional information on afterblow, the default
setting, and changing the setting, refer to Afterblow
Configuration.
Duct Air Temperature
Physical duct air temperature sensors are not used with
the front system. The air temperature in the air
distribution ducts is calculated by the BCM based on
the engine coolant temperature, coolant flow,
evaporator temperature, outside air temperature, solar
load, blower motor speed, air inlet door position, and
temperature door position information. The BCM uses
the values to calculate actuator position.
B39 Air Conditioning Evaporator Air Temperature
Sensor
The evaporator temperature sensor is a 2-wire negative
temperature coefficient thermistor. The sensor operates
within a temperature range of 40 to +85°C ( 40 to
+185°F). The sensor is installed near the evaporator
core to measure the air temperature exiting the core.
Based on vehicle operating conditions and operator
settings, the HVAC software algorithms will determine a
target evaporator air temperature. The operation of the
compressor solenoid will be adjusted as needed to
quickly reach and maintain the targeted temperature.
B1 Air Conditioning Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire
piezoelectric pressure transducer. A 5 V reference
voltage, low reference, and signal circuits enable the
sensor to operate. The A/C pressure signal can be
between 0.2 4.8 V. When the A/C refrigerant pressure
is low, the signal value is near 0 V. When the A/C
refrigerant pressure is high, the signal value is near 5 V.
The engine control module (ECM) converts the voltage
signal to a pressure value. When pressure is too high or
too low, the ECM will not allow the A/C compressor
clutch to engage.
G1 Air Conditioning Compressor
The A/C compressor uses a conventional belt driven
magnetic clutch to engage and mechanically turn the
compressor. When the A/C switch is pressed, the BCM
sends an A/C request message to the ECM via serial
data. If specific criteria is met, the ECM then grounds
the A/C compressor clutch relay control circuit, which
will switch the A/C compressor clutch relay. With the
relay contacts closed, battery voltage is supplied to the
permanently grounded A/C compressor clutch. The A/C
compressor clutch will then be activated.
This A/C system utilizes a variable displacement
solenoid valve to alter the amount of displacement
created by the turning of the compressor. The BCM
provides both battery voltage and a pulse width
modulated ground to the Q46 Air Conditioning
2023 - Colorado Electrical Body Builder Manual