8 Auto Heating & Air Conditioning
Evaporators 144
Evaporator Design and Construction / Types of
Evaporators / Parts Attached to the Evaporator
Condensers 146
Condenser Design
Accumulators 148
Accumulator Operation
Receiver-Driers 148
Desiccants
Pressure Relief Devices 150
Chapter 10:
Control Valves and Switches. . . . . . . . . . . . 153
Two Ways to Control Evaporator Temperature 154
Thermostatic Expansion Valves 154
Equalizers and Springs / H-blocks
Fixed Orifi ce Tubes 156
Electronic Expansion Valves 156
Evaporator Pressure Controls 157
Types of Evaporator Pressure Controls
Compressor Clutch Controls 161
Pressure Cycling Switches / Thermostatic
Temperature Cycling Switches / Pressure and
Temperature Sensors
System Protection Switches and Valves 163
Pressure Cutoff Switches / Temperature Cutoff
Switches / Thermal Limiters
Chapter 11:
Engine Cooling Systems and
Vehicle Heaters. . . . . . . . . . . . . . . . . . . . . . 167
Cooling System 168
Engine Cooling System Operation 168
Engine Cooling System Components 168
Liquid-cooled Engines 168
Coolants / Engine Water Jackets / Coolant Pump /
Coolant Pump Drive Belts / Radiator / Radiator Fans /
Thermostat / Coolant Hoses / Pressure Cap / Coolant
Recovery Systems / Drains and Air Bleeds
Air-Cooled Engines 178
Engine Cooling Fins / Blower / Shrouds / Oil Cooler /
Thermostat
Heating System 179
Heater—Liquid-Cooled Engine / Heater—Air-Cooled
Engine
Heating System Components 180
Liquid-Cooled System / Air-Cooled System
Chapter 12:
Air Delivery Systems. . . . . . . . . . . . . . . . . . 185
Air Handling Systems 186
Blowers and Motors 186
Blower Wheels / Blower Motors
Air Ducts and Heater/Evaporator Cases 187
Intake Ductwork / Heater and Evaporator Cases /
Output Ductwork / Vents / Independent Vents
Air Doors and Operating Devices 190
Blend Door / Diverter Doors / Door Operating
Devices / Cabin Filters
Chapter 13:
Manual HVAC Controls . . . . . . . . . . . . . . . 199
Control System Purposes 200
Temperature Control / Humidity Control / Airfl ow
Control
HVAC Control System Modes 200
Manual Control Systems 203
Control System Parts / Electrical and Electronic
Controls / Compressor Controls / HVAC Electrical
System Protection Devices / Control System
Operation
Chapter 14:
Automatic Temperature Control Systems . . 213
Automatic Control Systems 214
Types of Controls / Temperature Control Loops
Electronic Temperature Control Systems 215
Automatic and Semiautomatic Control Heads /
Control System Parts / Control System Operation /
Computer Self-diagnosis
Older Temperature Control Systems 223
Mechanical Temperature Control Systems /
Electromechanical Temperature Control Systems
Chapter 15:
Refrigeration System Diagnosis and Leak
Detection . . . . . . . . . . . . . . . . . . . . . . . . . . 227
Strategy-based Diagnostics 228
The Importance of Proceeding Logically 228
The Seven-Step Troubleshooting Procedure 228
Step 1—Determine the Exact Problem 228
Talking to the Driver
Step 2—Check for Obvious Problems 232
Step 3—Determine Which System Is Causing the
Problem 233
Functional and Performance Tests / Leak Detection
Step 4—Eliminate Other Causes of the Problem 243
Step 5—Recheck the Cause of the Problem 244
Always Perform Additional Tests / Deciding on
Needed Work
Step 6—Correct the Defect 246
Step 7—Recheck System Operation 246
Follow-up 246
Documentation of Repairs