HVAC System: Engine Cooling, Controls and Communication

Caution Danger: In order to reduce the chance of death, personal injury and/or property damage, carefully observe the instructions that follow: The service manuals of General Motors Company are intended for use by professional, qualified technicians. Attempting repairs or service without the appropriate training, tools, and equipment could cause death or injury to you or others. This could also damage the vehicle, or cause the vehicle to operate improperly. Proper vehicle service and repair are important to the safety of the service technician and to the safe, reliable operation of all motor vehicles. If you need to replace a part, use the same part number or an equivalent part. Do not use a replacement part of lesser quality. The service procedures we recommend and describe in this service manual are effective methods of performing service and repair. Some of the procedures require the use of tools that are designed for specific purposes. Accordingly, any person who intends to use a replacement part, a service procedure, or a tool that is not recommended by General Motors, must first establish that there is no jeopardy to personal safety or the safe operation of the vehicle. This manual contains various "Dangers," "Warnings" and "Cautions" that you must observe carefully in order to reduce the risk of personal injury during service or repair. Improper service or repair may damage the vehicle or render the vehicle unsafe. These "Dangers," "Warnings" and "Cautions" are not exhaustive. General Motors cannot possibly warn of all the potentially hazardous consequences of your failure to follow these instructions. This manual covers service procedures to vehicles that are equipped with a Supplemental Inflatable Restraint. Refer to the "Warnings" in Dangers, Warnings and Cautions in Supplemental Inflatable Restraint. Refer to Supplemental Inflatable Restraint component and wiring location views in Supplemental Inflatable Restraint before performing a service on or around Supplemental Inflatable Restraint components or wiring. Failure to follow these "Dangers," Warnings" and "Cautions" could cause air bag deployment, personal injury, or otherwise unnecessary Supplemental Inflatable Restraint repairs. In order to help avoid accidental air bag deployment and personal injury, whenever you service a vehicle that requires repair of the Supplemental Inflatable Restraint and another vehicle system, we recommend that you first repair the Supplemental Inflatable Restraint, then go on to the other system. June 2008

How to Complete the Audio Setup Wizard How to Complete the Connect Audio Setup Wizard Participants AW-1

How to Complete the Audio Setup Wizard How to Complete the Connect Audio Setup Wizard Once you have launched the course, select Meetings > Manage My Settings > Audio Setup Wizard Click Next. Click Test. Follow the directions. Click Next. AW-2

How to Complete the Audio Setup Wizard Choose your microphone or sound card from the dropdown list. Click Next. Click Record. Follow the directions. Click Next. Click Test Silence. Stay silent until the test is finished. Click Next. AW-3

Click Finish. HVAC System: Engine Cooling, Controls and Communication How to Complete the Audio Setup Wizard AW-4

Table of Contents Table of Contents Introduction... i-1 Module 1: Engine Cooling System Components... 1-1 Module 2: Heating, Ventilation and Air Conditioning Air Flow Control... 2-1 Module 3: Communication Networks and Air Conditioning System Sensors... 3-1 Instructor Name: Help Number: 800-825-5886, prompt 1 This manual contains information about service for the Heating, Ventilation and Air Conditioning (HVAC) System and its components. Always refer to applicable vehicle service information and appropriate Dealer Technical Service Bulletins for additional information regarding system operation and diagnostic/repair procedures. When this manual refers to a brand name, a number, or a specific tool, you may use an equivalent product in place of the recommended item. All information, illustrations and specifications in this manual are based on the latest product information available at the time of publication approval. General Motors reserves the right to make changes at any time without notice. No part of this book may be reproduced, stored in any retrieval system, or transmitted in any form or by any means (including but not limited to electronic, mechanical, photocopying, and recording) without prior written permission of General Motors Company. This applies to all text, illustrations, tables and charts. 2011 TC-1

Introduction Introduction i-1

Introduction Welcome to HVAC System: Engine Cooling, Controls and Communication Course Goal Upon successful completion of this course you will be able to apply concepts and procedures to properly diagnose Heating, Ventilation and Air Conditioning (HVAC) Systems concerns. Session Objectives Describe the Operation of Engine Cooling Components for HVAC system Describe HVAC air flow control methods Describe HVAC Communication Networks and A/C System Sensors Strategy Based Diagnostics Step 1. Understand and verify the customer concerns Step 2. Check that the vehicle is operating as designed Step 3. Conduct the Preliminary Checks-visual and operational Step 4. Perform the Diagnostic System Check-Vehicle Step 5. Check the Bulletins, Recalls and Preliminary Information Step 6. Perform the Diagnostics Step 7. Re-examine the Concern Step 8. Repair and Verify the Fix Special Instructions The diagnostic charts in this courseware are for reference only. Refer to Service Information when servicing the HVAC system and its components. i-2

Module 1: Engine Cooling System Components Module 1 Objective At the end of this module, you will be able to describe the Operation of Engine Cooling Components for HVAC system. Engine Cooling System The engine cooling components include the: Radiator Water Pump Thermostat Heater Core Coolant Surge Tank Coolant Cooling Fan NOTES: 1-2

Module 1: Engine Cooling System Components Radiator Heat transfer is the foundation of a vehicle s climate control system The Radiator transfers heat out of the coolant via a heat exchange process It is important that the Radiator is in good condition. It needs to be clean and free of debris like leaves, paper, dirt and grime Heat Transfer While inspecting for debris, note the condition of the cooling fins on the Radiator they should not be bent or folded over Radiator 1-3

Module 1: Engine Cooling System Components J-36847 Fin Straightening Tool Use fin straightening tool to correct damaged cooling fins Be sure to use the proper comb that matches the fin width of the Radiator that is being serviced This tool can also be used to straighten fins on Condensers, as well as, radiators J-36847 Fin Straightening Tool Water Pump Water Pump 1-4

Module 1: Engine Cooling System Components Thermostat Thermostat Thermostat placement varies according to the Engine and its design Thermostats located in the upper intake tend to allow temperatures to fluctuate more, plus or minus 6 C. (±10 F) Thermostats placed at the Radiator outlet hose or Water Pump inlet, results is tighter control, with less temperature fluctuation, plus or minus 3 C (±5 F) Heater Core The Heater Core is a heat exchanger Like the Radiator, it facilitates the heat transfer process The Heater Core transfers heat from coolant to the air entering the passenger compartment The Heater Core is located inside the HVAC housing Heater Core 1-5

Module 1: Engine Cooling System Components Coolant Surge Tank/Reservoir Coolant Surge Tank Some vehicles use a Coolant Surge Tank that is part of the pressurized cooling system Other vehicles have a reservoir, which is not part of the pressurized cooling system Since coolant expands and contracts when the engine fluctuates in temperature, both the Coolant Surge Tank and Reservoir can store excess coolant NOTE: Refer to Service Information (SI) for proper coolant type and fill procedures. Air Bleed During service, be aware that some engines contain an air bleed that must be opened when the system is refilled The air bleed helps prevent air from being trapped in the Engine Cooling System Air Bleed 1-6

Module 1: Engine Cooling System Components Coolant Coolant is used to lubricate the Water Pump shaft seal The majority of GM vehicles use DEX- Cool extended-life Coolant Extended-life Coolant contains anticorrosion properties and it prevents the water-coolant mix from freezing All GM cooling systems are sealed. A sealed system will pressurize as the engine warms the coolant. A pressurized system increases the boiling point of the coolant and water mixture DEX-COOL Antifreeze A typical mixture is 50/50 of water and coolant Some vehicles use a non-extended-life coolant; it is usually green or pink in color NOTE: Do NOT mix different types of coolants. That could lead to gelling. Cooling Fans Cooling fans facilitate the Heat Transfer process by providing air flow that moves through the Radiator and Condenser This action helps maintain proper engine temperature and supports the A/C system There are three type of cooling fans to be aware of: - Electric - Mechanical - Electro-viscous (EV) 1-7

Module 1: Engine Cooling System Components Electric Cooling Fan An Electric Cooling Fan usually has a relay that controls the current to the motor Electrical Cooling fans can also be controlled with Pulse Width Modulation or PWM Electric Cooling Fan Mechanical Cooling Fan Mechanical Cooling Fans are driven by a serpentine belt They are used in conjunction with the viscous clutch The clutch regulates fan speed based on engine compartment heat load Mechanical Cooling Fan 1-8

Module 1: Engine Cooling System Components Electro-Viscous Cooling Fan With an electro-viscous fan clutch, the Powertrain Control Module (PCM) sends a 5-volt PWM signal to a solid state relay The relay converts the 5-volt signal to a 12-volt PWM signal The PWM signal directly affects the amount of time the solenoid is energized The solenoid is internal to the fan clutch Electro-Viscous Cooling Fan When the solenoid in the fan clutch is energized, it opens the spring-loaded valve allowing fluid to flow from the storage chamber to the apply chamber of the Cooling Fan clutch When the solenoid is de-energized, the spring-loaded valve closes, blocking the path of the fluid to the coupling of the fan clutch, thus reducing fan speed NOTES: 1-9

Module 1: Engine Cooling System Components Video Outline: Coolant Flow The engine cooling system is designed to remove heat from engine components, while also allowing heat to travel to the passenger compartment When the vehicle starts, the Water Pump begins to circulate coolant through the engine, the cylinder head, and the heater core. As combustion starts to warm the coolant, heat is carried away through the coolant. After the temperature reaches approximately 88 degrees Celsius (190 degrees Fahrenheit), the thermostat starts to open (See Figure 1-1). This allows the hot coolant to flow through the radiator, releasing heat to the ambient air. As the coolant temperature decreases, the thermostat begins to close, and the coolant flow through the radiator is reduced. The thermostat regulates coolant flow through the radiator in order to maintain proper engine temperature. Engine Cooling System Figure 1-1 Thermostat opening 1-10

Module 1: Engine Cooling System Components Module 1 Summary We described the Engine Cooling System Components for the HVAC system, including the: Radiator Water Pump Thermostat Heater Core Coolant Surge Tank Coolant Cooling Fans 1-11

Module 2: HVAC Air Flow Control Module 2 Objective At the end of this module, you will be able to describe Heating, Ventilation and Air Conditioning (HVAC) air flow control methods Air Flow Through the HVAC Housing The air distribution system is comprised of passages and doors These doors control the flow of air through the Evaporator Core, Heater Core, and into the passenger compartment HVAC Housing 2-2

Module 2: HVAC Air Flow Control Adjusting Temperature Temperature Blend Door When the temperature setting is changed, the temperature or blend door moves inside the HVAC housing When the temperature is increased to the hot setting, the door moves, allowing more air to flow through the Heater Core When the temperature setting is colder, the door moves, decreasing the amount of air flow over the Heater Core 2-3

Module 2: HVAC Air Flow Control Adjusting Modes Selecting vent mode moves the door into a position that directs air out of the dash vents Vent Mode Bi-level mode changes the door position to direct air out of the floor and dash vents Bi-Level Mode Floor mode moves the door, directing air flow down through the floor vent This mode is more commonly used with heat setting Floor Mode 2-4

Module 2: HVAC Air Flow Control Adjusting Modes, Continued Defrost and Floor mode moves the doors into a position that directs air flow up to the windshield and down through the floor vents Defrost and Floor Mode In Defrost mode, the door moves directing all of the air flow up and out toward the windshield Defrost Mode 2-5

Module 2: HVAC Air Flow Control Fresh and Recirculation Modes Recirculation Modes Fresh/RECIRC modes may be one or two separate buttons depending on the vehicle They can be automatically controlled by the control head Fresh moves the recirculation door into a position that draws air from outside the vehicle into the passenger compartment Pressing the RECIRC button moves the recirculation door into a position that draws air that has already been cooled and dehumidified within the interior NOTES: 2-6

Module 2: HVAC Air Flow Control Film Valve Recirculation Modes The film valve contains slits that match up to openings within the HVAC housing to direct air flow One spool is driven by a motor, and the other spool is spring loaded in the opposite direction To change the mode, the motor operates to move the film to a different position, exposing other slits in the film Temperature is still controlled by a blend or temperature door Vehicles with film valves will also have cabin filters On this system, these filters must be inspected and replaced as indicated in Service Information (SI) or the Owner s Manual Cable Controlled Systems Cable-controlled systems are uncommon, but you may still see them on some vehicles These systems are mechanically actuated They use a cable that connects between the control head and the HVAC housing door A cable controlled system is usually adjustable 2-7

Module 2: HVAC Air Flow Control Vacuum Actuator Systems Another method used to control the movement of HVAC doors is a Vacuum Actuator System, which is used on some vehicles With this system, a rotary vacuum valve is used to direct vacuum to one of several vacuum actuators Vacuum Actuator Electric Actuators There are three types of electrical actuators: Two-Wire Three-Wire Five-Wire Two-Wire Actuator Two-Wire Actuator The Two-Wire Actuator is commonly found on RECIRC doors, they move from one extreme to the other The polarity of each wire can be reversed by the module to drive the actuator in the opposite direction Systems that use a two-wire actuator generally perform a calibration on these Actuators upon every key ON cycle 2-8

Module 2: HVAC Air Flow Control Electric Actuators, Continued Three-Wire Actuator A Three-Wire Actuator is typically found on temperature blend doors This actuator requires a power, a ground, and a signal wire Based on the voltage from the module, the actuator responds by moving to the commanded position A three-wire actuator cannot be calibrated Three-Wire Actuator Five-Wire Actuator Five-Wire Actuator Five-Wire actuators can come in several designs On the first design, two of the five wires supply power and ground The polarity of each of these wires can be changed to drive the actuator in either direction The remaining three wires make up a potentiometer circuit, which operates similarly to a throttle position sensor We get much more precise position information out of this type of fivewire actuator This is because it has its own internal position sensor, which provides feedback allowing the control module to monitor its position 2-9

Module 2: HVAC Air Flow Control Electric Actuators, Continued Stepper Motor Five-Wire Actuator Schematic Another type of Five-Wire Actuator is a Stepper Motor In this design, the HVAC control module supplies a 12-volt reference to the stepper motor Each of the four stepper motor coils is supplied a pulse width modulated signal on the low reference side by the HVAC module The motor can move the door to the requested position. Five-wire stepper motor actuators can be calibrated Tech Tip Never attempt to operate an actuator once it is removed from the HVAC housing If you do, the internal acutator gears will go beyond their designed travel limit, rendering the actuator inoperative 2-10

Module 2: HVAC Air Flow Control Climate Control Systems There are three types of Climate Control Systems: Single-zone Dual-zone Tri-zone Single-zone Climate Control Single-Zone Systems The Single-zone system receives inputs from various sensors and can automatically adjust blower speeds, air temperature and mode to maintain passenger comfort The control head has the Auto setting on it Dual-zone Climate Control Dual-Zone Systems This system can independently control the temperature for both the driver and the front seat passenger Some Dual-zone systems may not always display both temperatures on the control head Sometimes it is necessary to press the PASS button in order to check both the driver and front passenger temperature settings 2-11

Module 2: HVAC Air Flow Control Climate Control Systems, Continued Front Seat Control Rear Seat Control Tri-Zone Systems A Tri-Zone climate control system uses a self-contained rear unit with a separate evaporator, heater core and blower motor When enabled, they are controlled by either the front or rear control head Typically, the output circuits from the rear control head are sent directly to the front control head The front control head directly acts on requests from either the back or front, and it sends the request to the appropriate HVAC control module A separate blend door provides a separate control for rear seat passengers This allows adjustment of the temperature and rear blower speed separately from the front The rear module also has a separate mode control 2-12

Module 2: HVAC Air Flow Control Module 2 Summary In this module, we described: Heating, Ventilation and Air Conditioning (HVAC) airflow control methods, including: Vacuum Actuators Cable Controlled Film Valve Electric Actuators - Two-Wire actuators - Three-Wire actuators - Five-wire actuators Automatic climate control systems, including: Single-Zone Dual-Zone Tri-Zone 2-13

Module 3: Communication Networks and A/C System Sensors Module 3 Objective At the end of this module you will be able to: Describe Heating, Ventilation and Air Conditioning (HVAC) system communication networks and the operation of air conditioning system sensors that are used in automatic climate control systems Communication Networks There are three common communication networks found in today s vehicles: Class 2, which is being phased out High Speed, Mid Speed and Low Speed GM Local Area Networks (GMLAN) Local Interconnect Networks (LIN) A vehicle may have multiple communication networks. HVAC systems may use information from several modules to control various functions. These modules receive inputs from sensors around the vehicle to monitor the system s performance. The module, or modules, will use that information to control system functions. NOTES: 3-2

Module 3: Communication Networks and A/C System Sensors HVAC System Sensors System sensors for automatic HVAC operation are the: Ambient Air Temperature Sensor Inside Air Temperature Sensor Outlet Air Temperature Sensor Sunload Sensor Ambient Air Temperature Sensor Ambient Air Temperature Sensor The Ambient Air Temperature Sensor is located at the front of the vehicle, near the bumper or grille area This Sensor s input provides temperature display It also provides the HVAC controller with an input signal based on ambient air temperature A/C compressor clutch disables if temperature is at or below 0 C (32 F) The ambient air temperature sensor input also enables a more accurate temperature delivery 3-3

Module 3: Communication Networks and A/C System Sensors Inside Air Temperature Sensor Inside Air Temperature Sensor Typically, the Inside Air Temperature sensor is located in the dash panel or in the HVAC control The sensor has a small grille-like opening Depending on the vehicle, it can also be positioned in the headliner near the driver s door, or to the right of the steering column on the dash The Inside Air Temperature Sensor monitors the overall performance of the automatic HVAC system Outlet Air Temperature Sensor Outlet Air Temperature Sensor The Outlet Air Temperature sensor is typically located in left or right center vents or at floor vents Depending on the vehicle, it can be in various locations Outlet Air Temperature Sensors give us the immediate air temperature exiting the duct This allows the system to make adjustments to the temperature door to provide better temperature regulation 3-4

Module 3: Communication Networks and A/C System Sensors Tech Tip Be careful when installing ACR2000 temperature probes into these dash vents. The probes can dislodge the air temperature sensors, which could cause a customer concern ACR2000 Temperature Probes Sunload Sensor Sunload Sensor The Sunload sensor is located on upper dash near windshield It uses a photoconductive diode that provides current output It communicates with the controller, causing the controller to adjust the cooling requirement to enhance comfort This sensor also helps to control blower motor operation Sensors allow dual-zone systems to compensate for extra sunload 3-5

Module 3: Communication Networks and A/C System Sensors Module 3 Summary In this module, we described: Communication networks Air Conditioning System Sensors, including: - Ambient Air Temperature Sensor - Inside Air Temperature Sensor - Outlet Air Temperature Sensor - Sunload Sensor 3-6