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 | Th ermostatic Temperature Cycling Switches | Pressure and Temperature Sensors System Protection Switches and Valves . . . . . . . . . .163 Pressure Cutoff Switches | Temperature Cutoff Switches | Th ermal 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 | Th ermostat | Coolant Hoses | Pressure Cap | Coolant Recovery Systems | Drains and Air Bleeds Air-Cooled Engines . . . . . . . . . . . . . . . . . . . . . . . . .178 Engine Cooling Fins | Blower | Shrouds | Oil Cooler | Th ermostat Heating System. . . . . . . . . . . . . . . . . . . . . . . . . . . .179 Heating System Components . . . . . . . . . . . . . . . . .180 Heater Core | Heater Hoses | Auxiliary Coolant Pump 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 . . . . . .243 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 | Returning the Vehicle to the Customer Chapter 16 Refrigerant Recovery, Recycling, and Handling. . . . . . . . . . . . . . . . . . . 251 Refrigerant Service . . . . . . . . . . . . . . . . . . . . . . . . .252 Rules for Handling Refrigerants | Using a Refrigerant Identifi er | Adding Refrigerant to a Partially Charged System 8 Auto Heating and Air Conditioning