HVAC System: Engine Cooling, Controls and Communication

Copyright 2011, General Motors Company, All Rights Reserved

Course #S-AC07-04.01VCT

HVAC System: Engine Cooling, Controls and

Communication

Participant Guide Revised: 01/24/11

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

HVAC System: Engine Cooling, Controls and Communication How to Complete the Audio Setup Wizard

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HVAC System: Engine Cooling, Controls and Communication Table of Contents

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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

HVAC System: Engine Cooling, Controls and Communication Introduction

i-1

Introduction

HVAC System: Engine Cooling, Controls and Communication Introduction

i-2

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.

HVAC System: Engine Cooling, Controls and Communication Module 1: Engine Cooling System Components

Copyright 2011, General Motors Company, All Rights Reserved 1-1

MODULE 1 Engine Cooling System Components


1-2

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:


1-3

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


1-4

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


1-5

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)

Thermostat

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


1-6

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


1-7

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 anti-corrosion 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)


1-8

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 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


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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:


1-10

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.

Engine Cooling System

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.

Figure 1-1 Thermostat opening


1-11

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

HVAC System: Engine Cooling, Controls and Communication Module 2: HVAC Air Flow Control


MODULE 2 HVAC Air Flow Control


2-2

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


2-3

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


2-4

Adjusting Modes

Vent Mode

Selecting vent mode moves the door into a position that directs air out of the dash vents

Bi-Level Mode

Bi-level mode changes the door position to direct air out of the floor and dash vents

Floor Mode

Floor mode moves the door, directing air flow down through the floor vent

This mode is more commonly used with heat setting


2-5

Adjusting Modes, Continued

Defrost and Floor Mode

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 Mode

In Defrost mode, the door moves directing all of the air flow up and out toward the windshield


2-6

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:


2-7

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


2-8

Vacuum Actuator Systems

Vacuum Actuator

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

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


2-9

Electric Actuators, Continued

Three-Wire Actuator

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

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 five-wire actuator

This is because it has its own internal position sensor, which provides feedback allowing the control module to monitor its position


2-10

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


2-11

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


2-12

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


2-13

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

HVAC System: Engine Cooling, Controls and Communication Module 3: Communication Networks and A/C System Sensors


MODULE 3 Communication Networks and A/C

System Sensors


3-2

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:


3-3

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


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



3-4



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



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


3-5

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


3-6

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

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HVAC System: Engine Cooling, Controls and Communication