SYSTEM CONTROLS. CHAPTER 10. OBJECTIVES. Discuss Operation and Function of controls for Manual and Automatic Climate Control System. Discuss controlling system temperature by temperature and pressure actuated controllers. Discuss High and Low pressure switches and controls.
OBJECTIVES Discuss Operation and Function of controls for Manual and Automatic Climate Control System. Discuss controlling system temperature by temperature and pressure actuated controllers. Discuss High and Low pressure switches and controls. Understand how to trace air conditioning electrical schematics Understand vacuum system operation Describe the different types of evaporator blower motors.
SIMPLE CONTROL SYSTEM ONE WIRE FEEDS ALL PARTS CONSISTS OF MASTER ON/OFF SWITCH BLOWER CONTROL THERMOSTAT BLOWER MOTOR CLUTCH COIL CIRCUIT PROTECTION DEVICES PAGE 189C
COMPLEX CONTROL SYSTEM The more features the more complex the a/c system controls are. Usually shares fuses and circuit breakers with other systems Sometimes other system may be shown on the electrical schematic Page 190C
Page 241L MASTER CONTROL HEAD Page 243L page 214C Contains: Blower control Switch Temperature control Mode control Digital readout Schematic sometimes shows components separately
Page 197C BLOWER MOTORS All blower motors use a squirrel cage to move air Some motors have several windings (197C) Must make sure replacement motor is correct Can test with ohmmeter or ammeter Motor can be on ground side or feed side of circuit
SQUIRREL CAGE Page 197C
BLOWER MOTOR & HOUSING Page 197C
Page 247L COMPRESSOR CLUTCH Electromagnetic action Controlled by thermostat or pressure cycling switches System components protected by dumping diode across clutch coil To test you must use ohmmeter or ammeter. Clearance will affect amperage draw
COMPRESSOR DISCHARGE PRESSURE SWITCH High Pressure Cutoff Switch Usually located in high pressure lines or on compressor Not resettable, must replace 300-500 PSI Page 201C
Low Pressure Switch Can be used to shut off compressor clutch Can be used to cycle clutch (dual function) Found on low side or high side of system Can apply pressure to test using voltmeter or ohmmeter page 200C
COOLANT TEMPERATURE WARNING SYSTEMS Coolant system affect A/C operation One lamp coolant warning switch Two lamp coolant lamp warning switch Some don’t come on until 220 to 250 degrees
CONTROL DEVICES Actuators are either electrical or vacuum operated A/C system must have strong supply of vacuum to operate all the actuators in the system Sometimes must use motor operated vac pump or engine to test vacuum devices
Page 206C VACUUM CIRCUIT SOURCE 207C 207C Has check valve so vacuum maintained in system when going up hill Hoses color coded sometimes Must trace out like electrical.
Page 206C Single Action Vacuum Motor Only operates with one vacuum source. Vacuum only pulls in one direction. Can test with hand held vac pump Used to control doors