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HOMESERVICE MANUALSCHEVROLET2004MALIBU V6-3.5L VIN 8REPAIR AND DIAGNOSISRELAYS AND MODULESRELAYS AND MODULES - HVACCONTROL MODULE HVACDESCRIPTION AND OPERATION
2004 Chevrolet Malibu V6-3.5L VIN 8
Control Module HVAC: Description and Operation
2004 Chevrolet Malibu V6-3.5L VIN 8SECTION Description and Operation
HVAC SYSTEM - MANUAL
AIR DELIVERY
HVAC CONTROL MODULE
The HVAC control module is a non-GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive and ignition 3 voltage circuits provide power to the control module. The HVAC control module during defrost mode will change the a/c compressor LED status from on to off. The control head displays recirc, outside air, a/c and rear defrost feedback status through LED indicators. The HVAC control head will display NO COMMUNICATION when checking DTCs or doing a vehicle diagnostic system check refer to Diagnostic Trouble Code (DTC) List - Vehicle and Diagnostic System Check - Vehicle in Vehicle DTC Information. The control module supports the features as shown in the table.
HVAC SYSTEM - AUTOMATIC
HVAC CONTROL MODULE
The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from �C to �F by pressing the Auto button for a minimum of 3 seconds. The ignition 3 voltage circuit provides a device on signal. The control module supports the features as shown in the table.
BLOWER MOTOR CONTROL PROCESSOR
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
AIR DELIVERY
HVAC CONTROL MODULE
The HVAC control module is a non-GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive and ignition 3 voltage circuits provide power to the control module. The HVAC control module during defrost mode will change the a/c compressor LED status from on to off. The control head displays recirc, outside air, a/c and rear defrost feedback status through LED indicators. The HVAC control head will display NO COMMUNICATION when checking DTCs or doing a vehicle diagnostic system check refer to Diagnostic Trouble Code (DTC) List - Vehicle and Diagnostic System Check - Vehicle in Vehicle DTC Information. The control module supports the features as shown in the table.
HVAC SYSTEM - AUTOMATIC
HVAC CONTROL MODULE
The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The control module communicates on the low-speed data bus. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, then all HVAC DTCs and settings will be erased from KAM. The temperature display reading at the control head can be converted from �C to �F by pressing the Auto button for a minimum of 3 seconds. The ignition 3 voltage circuit provides a device on signal. The control module supports the features as shown in the table.
BLOWER MOTOR CONTROL PROCESSOR
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The processor supplies 12 volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.