SPECIAL TOOLS ........................................................................................................................................ 50-1-6

A/C THERMAL OPERATION ...................................................................................................................... 50-1-7

A/C SYSTEM COMPONENTS ................................................................................................................... 50-1-9

Cab HVAC Box Components - Automatic Temperature Control ............................................................... 50-1-9

Chassis Components .............................................................................................................................. 50-1-11

AUTOMATIC TEMPERATURE CONTROL (ATC) OPERATION ............................................................. 50-1-12

Operation Modes ..................................................................................................................................... 50-1-15

Automatic Mode .................................................................................................................................... 50-1-15

Defog Mode ........................................................................................................................................... 50-1-15

Automatic Operation Summary ............................................................................................................. 50-1-16

Defog/Dehumidify Operation Summary ................................................................................................. 50-1-17

ATC Fault Codes ..................................................................................................................................... 50-1-18

ATC Fault Code 111 .............................................................................................................................. 50-1-18

ATC Fault Code 112 .............................................................................................................................. 50-1-19

ATC Fault Code 115 .............................................................................................................................. 50-1-19

ATC Fault Code 116 .............................................................................................................................. 50-1-20

ATC Fault Code 120 .............................................................................................................................. 50-1-20

ATC Fault Code 121 .............................................................................................................................. 50-1-21

ATC Fault Code 122 .............................................................................................................................. 50-1-21

ATC Fault Code 125 .............................................................................................................................. 50-1-22

ATC Fault Code 126 .............................................................................................................................. 50-1-22

ATC Fault Code 127 .............................................................................................................................. 50-1-23

ATC Fault Code 128 .............................................................................................................................. 50-1-23

ATC Fault Code 129 .............................................................................................................................. 50-1-24

ATC Fault Code 130 .............................................................................................................................. 50-1-24

ATC Fault Code 131 .............................................................................................................................. 50-1-25

ATC Fault Code 132 .............................................................................................................................. 50-1-25

ATC Fault Code 133 .............................................................................................................................. 50-1-26

ATC Fault Code 134 .............................................................................................................................. 50-1-26

Locating System Problems Without Fault Codes ...................................................................................... 50-1-27

Controller-Based Resistance Tests ......................................................................................................... 50-1-27

ATC Controller Test (Connector J8 Test Points) ...................................................................................... 50-1-29

ATC Field Reported Symptoms/Causes ................................................................................................... 50-1-32

Compressor And Clutch ............................................................................................................................ 50-1-33

Operational Check .................................................................................................................................. 50-1-33

Electrical Test .......................................................................................................................................... 50-1-36

Compressor Clutch Control Circuit Test Procedure ................................................................................ 50-1-36

Service Note: Adjusting Clutch Air Gap .................................................................................................. 50-1-38

High And Low Pressure Switch Clutch Latching Circuit ............................................................................ 50-1-39

Background ............................................................................................................................................. 50-1-39

Possible Failure Modes - Fault Codes 129 and 134 ............................................................................... 50-1-40

Electrical Test .......................................................................................................................................... 50-1-41

High Pressure Switch and Circuit Test .................................................................................................... 50-1-41

Low Pressure Switch and Circuit Test .................................................................................................... 50-1-42

Heater Control Valve ................................................................................................................................. 50-1-43

Operational Check .................................................................................................................................. 50-1-43

Electrical Test .......................................................................................................................................... 50-1-44

Heater Control Valve Power, Signal and Ground Test ............................................................................ 50-1-44

Blower Speed And Temperature Control Potentiometers ......................................................................... 50-1-45

Background ............................................................................................................................................. 50-1-45

Possible Failure Modes - Fault Codes 120, 121 ..................................................................................... 50-1-45

Electrical Test .......................................................................................................................................... 50-1-46

Common Control Potentiometer and Circuit Test Procedure .................................................................. 50-1-46

T8010/T8020/T8030/T8040 MASTER TABLE OF CONTENTS

Table of Contents