MACK GU, CHU, MRU, CXU, LEU Service Manual

AIR

CONDITIONING

SYSTEM

Includes U.S. ’07 MACK® Chassis

GU (GraniteTM Series)

CHU and CXU (PinnacleTM Series)

MRU and LEU (TerraProTM Series) JULY 2007

(REVISED)

18-902

S E R V I C E M A N U A L

AIR CONDITIONING SYSTEM

SERVICE MANUAL

INCLUDES U.S. '07 MACK→ CHASSIS:

GU (Granite™ SERIES)

CHU AND CXU (Pinnacle™ SERIES)

MRU AND LEU (TerraPro™ SERIES)

JULY 2007	© MACK TRUCKS, INC. 2007
(REVISED — REPLACES ISSUE DATED APRIL 2006)	18-902

ATTENTION

The information in this manual is not all inclusive and cannot take into account all unique situations. Note that some illustrations are typical and may not reflect the exact arrangement of every component installed on a specific chassis.

The information, specifications, and illustrations in this publication are based on information that was current at the time of publication.

Concepts, data, and procedures described in this manual are considered applicable for use of all MACK factory-installed refrigerants, except where noted as pertaining exclusively to a specific type of refrigerant.

No part of this publication may be reproduced, stored in a retrieval system, or be transmitted in any form by any means including (but not limited to) electronic, mechanical, photocopying, recording, or otherwise without prior written permission of Mack Trucks, Inc.

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TABLE OF CONTENTS

TABLE OF CONTENTS

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TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 SAFETY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Advisory Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Service Procedures and Tool Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 PERSONAL SAFETY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 R-134a vs. R-12 System Component Differences (“Do's” and “Don'ts”) . . . . . . . . . . . . . . . . . . . 6 Additional Service Precautions for R-134a Refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 EXPLANATION OF NUMERICAL CODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Explanation of Three-Digit Numerical Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 ABOUT THIS MANUAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

DESCRIPTION AND OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	11
A/C SYSTEM FEATURES AND OPERATION — RED DOT SYSTEM [637] . . . . . . . . . . . . . . . . .	12
CH, CL and CX System Description [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
CH, CL and CX Cab Climate Control Panels [733] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
CH, CHN, CL, CX and CXN Millennium Sleeper Climate Control Panels [733] . . . . . . . . . . . .	14
DM, DMM, RB, RD6 and RD8 System Description [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15
DM, DMM, RB, RD6 and RD8 Climate Control Panel [733] . . . . . . . . . . . . . . . . . . . . . . . . . . .	15
FDM System Description [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	15
FDM Climate Control Panel [733] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
LE, LEU, MR and MRU Roof-Mounted A/C System Description [637] . . . . . . . . . . . . . . . . . . .	16
LE and LEU Heater Control Only [733] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
MR and MRU Cab-Mounted A/C System Description [637] . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
MR and MRU Cab-Mounted A/C System Climate Control Panel [733] . . . . . . . . . . . . . . . . . . .	17
CS and MS System Description [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
CS and MS Blower Control Switch [733] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	18
A/C SYSTEM FEATURES AND OPERATION — BLEND AIR SYSTEM [637] . . . . . . . . . . . . . . . .	19
CH, CHN, CL, CT, CV, CX and CXN System Description [637] . . . . . . . . . . . . . . . . . . . . . . . .	19
CH, CHN, CL, CT, CV, CX and CXN Cab Heater/Air Conditioner Control Panels [733] . . . . . .	20
A/C SYSTEM FEATURES AND OPERATION — BEHR SYSTEM [637] . . . . . . . . . . . . . . . . . . . .	23
CTP, CXP, CHU, CXU and GU BEHR System Description [637] . . . . . . . . . . . . . . . . . . . . . . .	23
CTP, CXP, CHU, CXU and GU Behr Cab Climate Control Panel [733] . . . . . . . . . . . . . . . . . .	24
V-MAC CONTROL OF THE ON/OFF FAN [230] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
Smart Fan Control Parameters [230] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
Fan Overrides [230] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
High Refrigerant Pressure Fan On Time [230] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
A/C SYSTEM FEATURES AND OPERATION — APADS→ CM812 MACK PART NO. 228RD33
(YELLOW LABEL) AND CM813 MACK PART NO. 228RD32 (WHITE LABEL) SYSTEM [637] . . .	25
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	25
Electrical I/O Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	26
Control and Diagnostic Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	27
Diagnostic Fault Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	27
Blink Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	28

COMPONENT LOCATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 CH, CHN, CL, CT, CX AND CXN COMPONENT LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . 30 DM, DMM, RB, RD6 AND RD8 COMPONENT LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . 31 FDM COMPONENT LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 LE, LEU, MR AND MRU WITH ROOF-MOUNTED A/C SYSTEM COMPONENT

LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 MR AND MRU CAB-MOUNTED A/C SYSTEM COMPONENT LOCATIONS [637] . . . . . . . . . . . . 32 CS AND MS COMPONENT LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

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CH, CV, CT AND CX MODELS WITH BLEND AIR HVAC SYSTEM COMPONENT

LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 CHN, CXN, CV (ASET™) AND CT MODELS WITH BLEND AIR HVAC SYSTEM COMPONENT LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 CXP AND CTP MODELS WITH BEHR HVAC SYSTEM COMPONENT LOCATIONS [637] . . . . . 36 CHU, CXU AND GU MODELS WITH BEHR HVAC SYSTEM COMPONENT

LOCATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 TROUBLESHOOTING MODELS WITH ROTARY CONTROL PANEL AND MILLENNIUM SLEEPER [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

CX Model A/C System without Constant Temperature Control (CTC) — Red Dot

System [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 CX, CH and CL Models with Rotary Control Panel A/C System with Constant Temperature Control (CTC) — Red Dot System [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Millennium Sleeper A/C Unit [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 CH, CHN, CL, CT, CV, CX and CXN Models (Bergstrom) with Blend Air Rotary Control

Panel and HVAC Unit — without Automatic Temperature Control (ATC) [637] . . . . . . . . . . . . . 46 CH, CHN, CL, CT, CV, CX and CXN Models with Blend Air Rotary Control Panel and HVAC Unit — with Automatic Temperature Control (ATC) [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Blend Air HVAC Unit Circuit-By-Circuit Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . 51 CH, CHN, CX and CXN Models with Blend Air Sleeper Systems Experiencing Evaporator Freezing and Icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

TROUBLESHOOTING BEHR HVAC SYSTEM — CTP, CXP, CXU, CHU AND GU

MODELS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Behr System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Unit Parts — Behr System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Behr System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 TESTING THE APADS→ CM812 AND CM813 MODULE [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Six-Pin Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Four-Pin Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 TROUBLESHOOTING APADS→ CM812 AND CM813 SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . 58 Blink Code Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Troubleshooting Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Diagnostic Flow Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

REPAIR INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 REPAIR INSTRUCTIONS — BERGSTROM HVAC UNIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Blower Motor Resistor Card Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Heater/Air Conditioner Cab Control Board Fuse — CH, CHN, CL, CT, CV, CX and CXN

Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 REPAIR INSTRUCTIONS — BEHR HVAC UNIT (CTP, CXP, CXU, CHU AND GU MODELS) . . . 70 Evaporator Replacement (Start of Production 3rd Quarter 2005 to 2nd Quarter 2007) . . . . . . . 70 CORRECTIVE ACTIONS FOR KNOWN HVAC MALFUNCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 94

Corrective Action for Sleeper Box Air Conditioner Evaporator Freezing and Icing — CH,

CHN, CV, CX and CXN Models with Blend Air-Type HVAC Systems . . . . . . . . . . . . . . . . . . . . 94 Corrective Action for Sticking or Binding Blend Air-Type Mode Box — CH, CHN, CL, CT,

CX and CXN Models with Blend Air-Type HVAC Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 A/C SERVICE RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Flushing the A/C System During Compressor Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Flushing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Safety Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

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Acceptable Flushing Fluid and Solvents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Component Flushing Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Back Flushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Flushing Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Residual Flushing Fluid Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Rear A/C System Evaporator and Hose Flushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Suction Side Flushing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

AIR CONDITIONING SYSTEM SPECIFICATIONS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Refrigerant and Oil Charge Levels [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

APADS→ CM812 AND CM813 A/C CONTROL SYSTEM [637] . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

SCHEMATIC & ROUTING DIAGRAMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . . 109
A/C SYSTEM REFRIGERANT CIRCUIT SCHEMATICS [637] . . . . . . . . . . . . . . . . . . . . . .	. . . . . 110
CH, CHN, CHU, CL, CT, CTP, CV, CX, CXN, CXU, GU and CXP Model A/C System . .	. . . . 110
DM, DMM, RB, RD6 and RD8 Model A/C System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 111
FDM Model A/C System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 112
LE, LEU, MR and MRU Models with Roof-Mounted A/C System . . . . . . . . . . . . . . . . . .	. . . . 113
MR and MRU Model with Cab-Mounted A/C System . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 114
CS and MS Model A/C System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 115
AIR DISTRIBUTION SCHEMATICS [733] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 116
CH and CL Air Delivery, Air Delivery Airflow and Air Control Logic — Red Dot System . . . . . 116
DM, DMM, RB, RD6 and RD8 Air Delivery and Air Control Logic — Red Dot System . .	. . . . 119
CH, CHN, CL, CT, CV, CX and CXN Airflow — Blend Air A/C System . . . . . . . . . . . . . .	. . . . 121
CTP, CXP, CHU, CXU and GU Airflow — Behr A/C System . . . . . . . . . . . . . . . . . . . . . .	. . . . 125
ELECTRICAL SYSTEM DIAGRAMS [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 133
CH, CL and CX A/C System Electrical Schematics — Red Dot System . . . . . . . . . . . . .	. . . . 133
DM, DMM, RB, RD6 and RD8 A/C System Electrical Schematics — Red Dot System	. . . . . 139
LE, LEU, MR and MRU Roof-Mounted A/C System Electrical Schematics — Red Dot
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 143
MR and MRU Cab-Mounted A/C System Electrical Schematics — Red Dot System . . .	. . . . 144
CS and MS A/C System Electrical Schematics — Red Dot System . . . . . . . . . . . . . . . .	. . . . 147
CH, CHN, CL, CT, CV, CX and CXN A/C System Electrical Schematics — Blend Air
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 149
CTP, CXP, CXU, CHU and GU Behr Cab A/C System Electrical Schematics . . . . . . . .	. . . . 151
APAds→ CM812 and CM813 Electrical Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . . . 154

SPECIAL TOOLS & EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 AIR CONDITIONING TOOLS REQUIRED FOR R-134a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Scavenger A/C Recovery Only Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 R-134a Smart Cart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 R-134a Pureguard2 Refrigerant Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Red Dot CTC2 Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 ACR4 (Black Shroud) Recovery and Recycling Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Mode Actuator Removal and Installation Tools (BEHR Climate Unit) . . . . . . . . . . . . . . . . . . . 159

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DISASSEMBLED VIEWS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	161
ASSEMBLY VIEW AND PARTS IDENTIFICATION [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	162
CH, CL and CX Cab Unit Parts [637] — Red Dot System . . . . . . . . . . . . . . . . . . . . . . . . . . . .	162
CH, CHN, CHU, CL, CX, CXN, CXP and CXU Millennium Sleeper Unit Parts [637] — Red
Dot System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	164
DM, DMM, RB, RD6 and RD8 Cab Unit Parts [637] — Red Dot System . . . . . . . . . . . . . . . .	165
FDM Cab Unit Parts [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	166
LE, LEU, MR and MRU Roof-Mounted Unit Parts [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	167
MR and MRU Cab-Mounted Unit Parts [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	169
CS and MS Cab Unit Parts [637] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	170
CH, CHN, CL, CT, CV, CX and CXN Cab Unit Parts [637] — Blend Air System . . . . . . . . . . .	172
CTP, CXP, CXU, CHU and GU Unit Parts [637] — Behr Cab A/C System Kinematics . . . . . .	173
CTP, CXP, CXU, CHU and GU Behr A/C System [637] — Service View (Complete Unit) . . . 174
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	175

Page vii

NOTES

Page viii

INTRODUCTION

INTRODUCTION

Page 1

INTRODUCTION

SAFETY INFORMATION

Advisory Labels

Cautionary signal words (Danger-Warning-Caution) may appear in various locations throughout this manual. Information accented by one of these signal words must be observed to minimize the risk of personal injury to service personnel, or the possibility of improper service methods which may damage the vehicle or cause it to be unsafe. Additional Notes and Service Hints are used to emphasize areas of procedural importance and provide suggestions for ease of repair. The following definitions indicate the use of these advisory labels as they appear throughout the manual:

Danger indicates an unsafe practice that could result in death or serious personal injury. Serious personal injury is considered to be permanent injury from which full recovery is NOT expected, resulting in a change in life style.

Warning indicates an unsafe practice that could result in personal injury. Personal injury means that the injury is of a temporary nature and that full recovery is expected.

Caution indicates an unsafe practice that could result in damage to the product.

Note indicates a procedure, practice, or condition that must be followed in order for the vehicle or component to function in the manner intended.

A helpful suggestion that will make it quicker and/or easier to perform a procedure, while possibly reducing service cost.

Page 2

INTRODUCTION

Service Procedures and Tool Usage

Anyone using a service procedure or tool not recommended in this manual must first satisfy himself thoroughly that neither his safety nor vehicle safety will be jeopardized by the service method he selects. Individuals deviating in any manner from the instructions provided assume all risks of consequential personal injury or damage to equipment involved.

Also note that particular service procedures may require the use of a special tool(s) designed for a specific purpose. These special tools must be used in the manner described, whenever specified in the instructions.

1.Before starting a vehicle, always be seated in the driver's seat, place the transmission in neutral, apply the parking brakes, and push in the clutch pedal. Failure to follow these instructions could produce unexpected vehicle movement, which can result in serious personal injury or death.

2.Before working on a vehicle, place the transmission in neutral, set the parking brakes, and block the wheels. Failure to follow these instructions could produce unexpected vehicle movement, which can result in serious personal injury or death.

Engine-driven components such as Power Take-Off (PTO) units, fans and fan belts, driveshafts and other related rotating assemblies, can be very dangerous. Do not work on or service engine-driven components unless the engine is shut down. Always keep body parts and loose clothing out of range of these powerful components to prevent serious personal injury. Be aware of PTO engagement or nonengagement status. Always disengage the PTO when not in use.

Do not work under a vehicle that is supported only by a hydraulic jack. The hydraulic jack could fail suddenly and unexpectedly, resulting in severe personal injury or death. Always use jackstands of adequate capacity to support the weight of the vehicle.

Before towing the vehicle, place the transmission in neutral and lift the rear wheels off the ground, or disconnect the driveline to avoid damage to the transmission during towing.

REMEMBER,

SAFETY . . . IS NO ACCIDENT!

Page 3

INTRODUCTION

Mack Trucks, Inc. cannot anticipate every possible occurrence that may involve a potential hazard. Accidents can be avoided by recognizing potentially hazardous situations and taking necessary precautions. Performing service procedures correctly is critical to technician safety and safe, reliable vehicle operation.

The following list of general shop safety practices can help technicians avoid potentially hazardous situations and reduce the risk of personal injury. DO NOT perform any services, maintenance procedures or lubrications until this manual has been read and understood.

Perform all service work on a flat, level surface. Block wheels to prevent vehicle from rolling.

DO NOT wear loose-fitting or torn clothing. Remove any jewelry before servicing vehicle.

ALWAYS wear safety glasses and protective shoes. Avoid injury by being aware of sharp corners and jagged edges.

Use hoists or jacks to lift or move heavy objects.

NEVER run engine indoors unless exhaust fumes are adequately vented to the outside.

Be aware of hot surfaces. Allow engine to cool sufficiently before performing any service or tests in the vicinity of the engine.

Keep work area clean and orderly. Clean up any spilled oil, grease, fuel, hydraulic fluid, etc.

Only use tools that are in good condition, and always use accurately calibrated torque wrenches to tighten all fasteners to specified torques. In instances where procedures require the use of special tools which are designed for a specific purpose, use only in the manner described in the instructions.

Do not store natural gas powered vehicles indoors for an extended period of time (overnight) without first removing the fuel.

Never smoke around a natural gas powered vehicle.

Page 4

INTRODUCTION

PERSONAL SAFETY

Refrigerant is transparent and colorless as a gas or liquid. Since it boils at sea-level temperatures of −29.8°C (−21.6°F), refrigerant is a vapor at normal ambient temperatures and pressures.

Refrigerant is flammable when in contact with open flame and will form into poisonous substances when exposed to flame or high temperature.

These characteristics make it mandatory to observe special precautions when handling refrigerant during maintenance/service procedures that involve refrigerant recovery/recycling, recharging, and monitoring of refrigerant in the air conditioning (A/C) system.

Become familiar with the following safety guidelines before attempting to perform any work on the A/C system.

Always wear safety goggles or glasses to

protect your eyes. Since refrigerant boils at extremely low temperatures (−29.8°C, −21.6°F), direct contact with skin will produce frostbite. Treat affected areas of skin as done for frostbite. In the event of accidental contact with eyes, flood eyes immediately with cool water, and then treat with mineral oil or clear petroleum jelly followed by boric acid rinse. Report to a doctor or hospital as soon as possible.

Use care when working around hot components and pressure lines or personal injury could result.

Discharge the system using a refrigerant recovery/recycling station before performing any repair work on the system. Use a UL/SAE-approved recovery/recycling station (i.e., Kent-Moore J 39650, J 39500-B or equivalent.)

Do not release refrigerant into the atmosphere, especially in non-vented areas. If there are any pits in the shop, danger of suffocation is possible because refrigerant is heavier than air.

Never perform any welding on parts of a closed air conditioning system, or in its immediate vicinity. Whether or not the system is charged with refrigerant, the heat developed causes excessive pressure that can damage the system or even cause an explosion.

Do not drop or throw refrigerant cylinders. Do not expose refrigerant cylinders to prolonged sunlight or any other uncontrolled source of heat.

Due to the potential for personal injury and equipment damage involved with liquid charging, Mack Trucks, Inc. recommends only low-side vapor charging.

For system charging, Mack Trucks, Inc. recommends using a portable charging station equipped with a “dial-a-charge” heated charging cylinder (i.e., Kent-Moore J 39500-B or equivalent). This device provides control of refrigerant supply heat and pressure levels, and adjusts for volume fluctuation in refrigerant caused by temperature changes.

Never use direct flame or electric heaters in direct contact with the refrigerant container. High temperatures can raise the pressure to a dangerous level.

Never attempt to connect servicing equipment (e.g., manifold gauge set) while the engine is running.

Never open the high-side hand valve of the gauge set when the manifold gauge set is connected to both the air conditioning system and refrigerant supply cylinder while the A/C system is operating. If hot, high-pressure refrigerant is forced through the gauge to the refrigerant supply cylinder, it could cause the cylinder to rupture and cause personal injury.

Never mix DuPont SUVA→ refrigerants with air for purposes of leak testing. Laboratory tests have shown these refrigerant products to be combustible when present with high concentrations of air above atmospheric pressure.

If recharging a chassis equipped with DuPont SUVA→ refrigerant product, never

heat the refrigerant supply cylinder above 52°C (125°F). Doing so may increase cylinder pressure beyond the capacity of the relief devices, causing the cylinder to rupture or shatter.

Page 5

INTRODUCTION

R-134a vs. R-12 System Component Differences (“Do's” and “Don'ts”)

REFRIGERANT LUBRICANT

If the wrong oil is installed into the A/C system being serviced, system performance will suffer and compressor life will be greatly reduced.

R-134a refrigerant is NOT a direct replacement for R-12 refrigerant because it uses PAG (polyalkylene glycol) as a lubricant instead of the mineral based oil used with R-12.

The following service guidelines apply:

1.DO NOT install R-134a refrigerant into a system containing mineral-based oil lubricant.

2.DO NOT install R-12 refrigerant into a system containing PAG lubricant.

3.DO NOT install mineral-based oil lubricant into a system charged with R-134a refrigerant.

4.DO NOT install PAG lubricant into a system charged with R-12 refrigerant.

5.During reassembly of system components and lines, always use mineral lubricant to lubricate the O-rings for R-134a charged systems.

It is still recommended to use mineral-based oil to lubricate O-rings for R-12 charged systems.

Continue to use MOLYKOTE 1000 (Dow Corning) to lubricate male connectors (threads only) to prevent later difficulty in disassembly of hose fittings from mating components.

A/C SYSTEM HOSES

Always install correct replacement hoses specified for the A/C system being serviced (R-134a or R-12 refrigerant charge). Use of improper hoses may cause a hose to rupture, resulting in personal injury or death.

A/C systems charged with R-134a refrigerant place increased demand on system hoses. When servicing an A/C system, be sure to use only MACK→ OEM replacement hoses.

RECEIVER DRYER

A/C systems charged with R-134a refrigerant are equipped with a receiver/dryer containing different desiccant material than used in the receiver/dryer of R-12 charged systems.

A receiver/dryer designed for use with an R-134a system can also be installed into an R-12 system.

1.DO NOT install a receiver/dryer designed for use with an R-12 system into an R-134a charged system. Otherwise, the desiccant material will break down and plug the A/C system.

2.SIGHT GLASS:

a.Under “medium-to-high” HIGH SIDE pressures, the PAG lubricant drops out of solution from the refrigerant R-134a. Even with a fully charged system the sight glass will appear white and milky.

b.DO NOT add more R-134a refrigerant to a system based only on the sight glass indication. The best method is to recover all refrigerant, then recharge the system using the required amount of refrigerant specified on the under-hood A/C system information label.

Page 6

INTRODUCTION

EXPANSION VALVE

For an R-134a charged system, the sensing tube of the expansion valve is filled with R-134a refrigerant. The sensing tube of an R-12 system is filled with R-12 refrigerant.

1.DO NOT install an expansion valve designed for an R-12 system into an R-134a charged system.

2.DO NOT install an expansion valve designed for an R-134a system into an R-12 charged system.

Additional Service Precautions for R-134a Refrigerant

Be sure to review ALL precautions. All A/C system service must be performed by qualified, certified A/C technicians! The following guidelines are listed to emphasize ADDITIONAL precautions required for performing service on R-134a charged systems.

PERSONAL PROTECTION

Always wear safety goggles or glasses to protect your eyes. Since R-134a refrigerant boils at extremely low temperatures, direct contact with skin will produce frostbite. Treat affected areas of skin as done for frostbite. In the event of accidental contact with eyes, DO NOT rub the eyes. Proceed to flood the eyes immediately with cool water, then report to a doctor or hospital as soon as possible.

TOXIC GAS

R-134a refrigerant is not combustible. However, in the presence of heat it changes to poisonous phosgene gas which can cause serious damage to the respiratory system or death.

Never discharge refrigerant near an open flame or electrical heating element.

Never smoke in an area where refrigerant is used or stored.

PRESSURIZED A/C SYSTEM DANGER

R-134a refrigerant must be recovered from the A/C system before any system components are removed or replaced. Removing components from a pressurized system can cause serious injury or death.

SYSTEM PERFORMANCE TESTING

Some vehicles have been redesigned with a larger condenser for R-134a refrigerant. Consequently the running HIGH SIDE pressure for these vehicles may be lower than comparable readings for previous R-12 charged vehicles.

INDUSTRY-APPROVED RECOVERY/RECYCLING EQUIPMENT

Always use approved refrigerant recovery/recycling equipment when servicing an R-134a system. Rapid evaporation of escaping refrigerant can displace oxygen in the work area, creating the hazard of suffocation or brain damage, especially in small or enclosed spaces.

SERVICE HOSE FITTINGS

Fittings on service hoses intended for R-134a charged systems are standard Metric SAE quick-disconnect fittings that will work only on R-134a systems.

MANIFOLD GAUGE SET

Never use the same manifold gauge set for servicing BOTH R-134a and R-12 charged systems.

Be sure to use a manifold gauge set that is dedicated to R-134a charged systems only.

COMPRESSOR LUBRICANT REFILL

Each R-134a charged chassis is factory equipped with an under-hood A/C system information label. This label provides the applicable lubricant refill (volume) specification plus the recommended type of refrigerant oil (PAG, or POE for CL models with Cummins ISX engine using CCI compressor) to use in the system.

Page 7

INTRODUCTION

ASSEMBLY LUBRICANT

During reassembly of system components and lines, always lubricate O-rings and other system components for R-134a charged systems, using mineral oil.

Continue to use MOLYKOTE 1000 (Dow Corning) to lubricate male connectors (threads only) to prevent later difficulty in disassembly of hose fittings from mating components.

LEAK TESTING

Never mix R-134a refrigerant with air for purposes of leak testing. Laboratory tests have shown this type of refrigerant to be combustible when present with high concentrations of air above atmospheric pressure.

SYSTEM CHARGING

If recharging an R-134a system, never heat the refrigerant supply cylinder above 52°C (125°F). Exceeding this temperature may cause cylinder pressure to increase beyond the capacity of the relief devices, resulting in a ruptured or shattered cylinder.

Since R-134a refrigerant is of lower density than R-12 refrigerant, the amount (lbs.) of R-134a required to charge a comparable air conditioning system is also reduced.

Each R-134a charged chassis is factory equipped with an under-hood A/C system information label. This label will provide the applicable R-134a system charge specification plus R-134a product recommendation.

Page 8

INTRODUCTION

EXPLANATION OF NUMERICAL CODE

Explanation of Three-Digit

Numerical Code

The organization of MACK service manuals has been upgraded to standardize manual content according to a reference system based on component identification. The new reference system will help link the information contained in this publication with related information included in other MACK service/warranty publications, such as associated service bulletins, warranty manuals, and MACK Service Labor Time Standards.

The system is based on a numerical code, the first digit of which identifies the general component grouping as listed here:

GROUP 000 — GENERAL DATA

GROUP 100 — CHASSIS

GROUP 200 — ENGINE

GROUP 300 — CLUTCH, TRANSMISSION, TRANSFER CASE AND PTO

GROUP 400 — STEERING, AXLES, WHEELS AND TIRES, DRIVELINE

GROUP 500 — BRAKES, AUXILIARY SYSTEMS

GROUP 600 — CAB, TRUCK BODY

GROUP 700 — ELECTRICAL

The second two digits of the three-digit code are used to identify the system, assembly or subassembly, as appropriate, within each of the groupings. The codes applicable to this publication are shown at SECTION HEADINGS, as necessary, to guide you to specific component information.

Additionally, a two-character alpha code (i.e., [VG] VALVE, EXPANSION) is shown with each operation. This alpha code, in combination with the three-digit Group number, identifies the specific assembly, subassembly or part, and directly relates to the first five positions of the operation code listed in MACK Service Labor Time Standards.

Numerical Code

Page 9

INTRODUCTION

ABOUT THIS MANUAL

This publication will assist the experienced heavy-duty truck technician in diagnosis of the MACK family of air conditioning (A/C) systems. This manual is designed to be a supplement to the Red Dot, BERGSTROM and BEHR service materials.

Use only genuine MACK replacement parts for servicing these A/C systems. Genuine MACK parts are available through your nearest MACK branch, distributor, service dealer or parts dealer.

DO NOT modify or rework parts. DO NOT use substitute parts. A modified or substitute part may result in loss of vehicle control and possible personal injury.

Proper service and repair is important for safe and reliable operation of the A/C system. The service procedures recommended by MACK and described in this technical publication are effective methods of performing maintenance. Some of these operations (e.g., removal and installation of bushings) may require the use of tools made in the shop.

A technician who decides to use a service procedure or tool not recommended by MACK must first satisfy himself that the selected method or tool will not jeopardize either his safety or that of the vehicle.

Throughout are various Dangers, Warnings, Cautions, Notes and Service Hints. Read these carefully to minimize the risk of personal injury and to ensure using proper methods. Improper service can damage the vehicle or cause it to be unsafe to operate. Also understand that these Dangers, Warnings, Cautions, Notes and Service Hints are not exhaustive. MACK cannot evaluate and advise the service trade of all conceivable ways in which service may be performed or of all the hazards involved.

Be sure to use refrigerant recovery, recycle or test equipment according to manufacturer’s instructions.

Page 10

DESCRIPTION AND OPERATION

DESCRIPTION AND OPERATION

Page 11

DESCRIPTION AND OPERATION

A/C SYSTEM FEATURES AND OPERATION — RED DOT SYSTEM [637]

CH, CL and CX System Description [637]

CH AND CL MODEL CAB

The CH and CL model cab A/C system is a cable-operated water valve control system. The control cable to the water valve limits the amount of coolant flow through the heater core depending on the temperature control lever position.

CX MODEL CAB WITHOUT CONSTANT TEMPERATURE CONTROL (CTC)

The CX model cab A/C system is a cable-operated water valve control system. The control cable to the water valve limits the amount of coolant flow through the heater core depending on the temperature control knob position.

CX MODEL CAB AND CH AND CL MODEL CABS WITH CONSTANT TEMPERATURE CONTROL (CTC)

The CX model cab and CH and CL model cabs with Constant Temperature Control (CTC) A/C system use an electronically controlled water valve control system. The CTC maintains a pre-selected temperature by pulsating the flow of coolant through the heater core. The air output temperature is monitored by the circuit board inside the A/C unit, and any change in output temperature activates the circuit board, energizing or de-energizing the solenoid valve. The solenoid valve, located inside the A/C unit, controls the air supply that opens or closes the water valve.

MILLENNIUM SLEEPER

The CH, CL and CX model millennium sleeper A/C systems use a rotary actuator motor controlled blend air door system. The actuator motor controls the position of the blend air door depending upon the temperature control knob position.

CH, CL and CX Cab Climate Control Panels [733]

Figure 1 — CH and CL Cab Climate Control Panel with Lever Style Controls

1.	Blower Control Switch	3. Temperature Control Lever
2.	Mode Selection Lever

The CH and CL cab climate control panel uses the following switch and levers to control the A/C system:

1.The four-position blower control switch allows control of the amount of air delivered through the vents.

2.The mode selection lever allows the operator to choose the type of climate and air direction in the cab.

3.The temperature control lever allows the operator to adjust the temperature of the air in the cab.

Page 12

DESCRIPTION AND OPERATION

	Figure 2 — CX and Current CH Cab Climate Control Panel with Rotary Style Controls
1.	Blower Control Knob	4.	Fresh/Recirculation Switch
2.	Temperature Control Knob	5.	On/Off Switch
3.	Mode Selection Knob

The CX cab and current CH cab climate control panels use the following knobs and switches to control the A/C system:

1.The blower control knob is a five-position knob used to control the amount of air delivered through the vents.

2.The temperature control knob allows the operator to adjust the temperature of the air in the cab.

3.The mode selection knob allows the operator to choose the air direction in the cab. The knob may be adjusted at any position to obtain any desired blend between Panel and Floor, or between Floor and Defrost.

4.The fresh/recirculation switch allows the operator to choose fresh outside air, or to recirculate inside air. “Recirc” allows for better A/C performance.

5.The on/off switch is for controlling the A/C.

Page 13

DESCRIPTION AND OPERATION

CH, CHN, CL, CX and CXN Millennium Sleeper Climate Control Panels [733]

Figure 3 — CL Lever Style Climate Control Panel (Millennium Sleeper)
1. Fan Control Lever		3. Temperature Control Knob
2. Mode Selection Lever

The CL lever style Millennium Sleeper climate control panel uses the following levers and knob to control the A/C system:

1.The fan control lever is a three-position lever used to control the amount of air delivered through the sleeper box air vents.

2.The mode selection lever allows the operator to choose between OFF, HEAT or A/C.

3.The temperature control knob allows the operator to adjust the temperature of the air in the sleeper.

Figure 4 — CX and CH Rotary Style Climate Control Panel (Millennium Sleeper)

1.	Blower Control Knob	3. Temperature Control Knob
2.	Mode Selection Knob

The CX and CH rotary style Millennium Sleeper climate control panel uses the following knobs to control the A/C system:

1.The blower control knob is a three-position knob used to control the amount of air delivered through the vents.

2.The mode selection knob allows the operator to choose HEAT, A/C or OFF.

3.The temperature control knob allows the operator to adjust the temperature of the air in the cab.

Page 14

DESCRIPTION AND OPERATION

DM, DMM, RB, RD6 and RD8 System

Description [637]

The DM, DMM, RB, RD6 and RD8 model A/C systems use a cable-operated water valve control system. The control cable to the water valve limits the amount of coolant flow through the heater core depending upon the temperature control knob position.

DM, DMM, RB, RD6 and RD8 Climate Control Panel [733]

			Figure 5 — Climate Control Panel
1. Blower Control Switch					3. Mode Selection Lever
2. Temperature Control Lever

The DM, DMM, RB, RD6 and RD8 model climate control panel uses the following switch and levers to control the A/C system:

1.The blower control switch is a four-position switch used to control the amount of air delivered through the vents.

2.The temperature control lever allows the operator to adjust the temperature of the air in the cab.

3.The mode selection lever allows the operator to choose the type of climate and air direction in the cab.

FDM System Description [637]

The FDM model cab A/C system uses a water valve controlled flow-through system. When the mode selection switch is placed in the A/C position, coolant flow to the water valve is shut off.

Page 15

DESCRIPTION AND OPERATION

FDM Climate Control Panel [733]

Figure 6 — Climate Control Panel

1. Blower Control Switch	2. Mode Selection Switch

The FDM model climate control panel uses the following switches to control the A/C system:

1.The blower control switch is a three-position switch used to control the amount of air delivered through the vents.

2.The mode selection switch allows the operator to choose between A/C and HEAT.

LE, LEU, MR and MRU

Roof-Mounted A/C System

Description [637]

The LE, LEU, MR and MRU model cab A/C systems with roof-mounted units use a flow-through system.

LE and LEU Heater Control Only [733]

Figure 7 — LE and LEU Heater Control

1.	Blower Control Switch	3. Air Direction Lever
2.	Temperature Control Lever

The LE and LEU model climate control panel uses the following switch and levers to control the heater system:

1.The blower control switch is a four-position switch used to control the amount of air delivered through the vents.

2.The temperature control lever allows the operator to adjust the temperature of the air in the cab.

3.The air direction lever allows the operator to choose the air direction in the cab.

Page 16

DESCRIPTION AND OPERATION

MR and MRU Cab-Mounted A/C

System Description [637]

The MR and MRU model cab with integral front-panel unit A/C systems use a cable-operated water valve control system. The control cable to the water valve limits the amount of coolant flow through the heater core depending on the temperature control lever position.

MR and MRU Cab-Mounted A/C System Climate Control Panel [733]

Figure 8 — Climate Control Panel

1.	Blower Control Switch	4.	Fresh/Recirculation Selection Lever
2.	A/C Mode (ON/OFF) Switch	5.	Air Direction Lever
3.	Temperature Control Lever

The MR and MRU model climate control panel uses the following switches and levers to control the A/C system:

1.The blower control switch is a four-position switch used to control the amount of air delivered through the vents.

2.The A/C mode switch allows the operator to turn the A/C on or off.

3.The temperature control lever allows the operator to adjust the temperature of the air in the cab.

4.The fresh/recirculation selection lever allows the operator to choose the type of air circulating within the cab.

5.The air direction lever allows the operator to choose the air direction in the cab.

CS and MS System Description [637]

The CS and MS model cab A/C systems use a flow-through system.

Page 17

DESCRIPTION AND OPERATION

CS and MS Blower Control Switch [733]

Figure 9 — Blower Control Switch

1. Blower Control Switch

The blower control switch is a four-position switch used to control the amount of air delivered through the vents.

Page 18

DESCRIPTION AND OPERATION

A/C SYSTEM FEATURES AND OPERATION — BLEND AIR SYSTEM [637]

CH, CHN, CL, CT, CV, CX and CXN System Description [637]

The blend air Heating, Ventilation and Air Conditioning (HVAC) cab unit for the CH, CHN, CL, CT, CV, CX and CXN chassis is basically a self-contained unit secured to the cab using four bolts. A snap-in fresh air duct connects the unit to

the cab dash-panel opening. This unit uses blend door technology to maintain and regulate the desired temperature level within the cab. This design eliminates the use of the cable-operated heater control water valve that is used in Red Dot HVAC systems. The major components of the unit are common and consist of the following:

Heater core

A/C evaporator core

Blower motor

Fresh air, mode and blend doors

Control panel

Figure 10 — Blend Air HVAC Unit

Three versions of the blend air HVAC unit are available. The regulated or Automatic Temperature Controlled (ATC) unit, the base or manual-temperature controlled unit and the heater-only unit. These units feature five primary modes of air flow with fresh air and recirculation control and a five-position fan switch ranging from 0 (Off) to 4 (High). The ATC unit uses a thermistor-type air temperature sensor to automatically maintain the desired cab temperature through the use of electronically controlled electric blend door actuators. The manually controlled base unit uses cables to manually position the blend doors for desired temperature and air flow direction.

BLEND AIR HVAC UNIT OPTIONS

Units	CH	CV	CX
Available	Chassis	Chassis	Chassis
Regulated	X	X	X
(ATC) Unit
Manual	X	X	X
Control Unit
Heater-Only		X
Unit

Page 19

DESCRIPTION AND OPERATION

CH, CHN, CL, CT, CV, CX and CXN

Cab Heater/Air Conditioner Control

Panels [733]

The control panels are integrated into the HVAC unit and consist of three rotary controls for blower (fan) speed, temperature control and air flow

REGULATED (ATC) CONTROL PANEL

direction. There is either one or two push-button switches located on the control panel for the ATC and manual units. The control panel for the heater-only unit has no push button switches. A lever is used on the manual and heater-only control panels to select fresh or recirculated air into the cab.

		Figure 11 — Regulated (ATC) Control Panel
1.	Blower Rotary Control Knob			4.	Recirculation Push-Button Switch
2.	Temperature Rotary Control Knob			5.	A/C On/Off Push-Button Switch
3.	Mode Rotary Control Knob			6.	ATC Air Grid

The Regulated (ATC) control panel uses the following rotary control knobs and push-button switches to operate the A/C system:

1.The blower rotary control knob is a five-position switch used to control the amount of air delivered through the vents.

2.The temperature rotary control knob allows the operator to adjust the temperature of the air in the cab. (The temperature is regulated and maintained electronically after desired temperature position is chosen.)

3.The mode selection rotary control knob allows the operator to choose the direction of air in the cab (panel, panel/floor, floor, defrost/floor, and defrost positions).

4.The recirculation (RECIRC) push-button switch allows the operator to choose the type of air circulating within the cab (fresh or recirculated air).

5.The A/C push-button switch allows the operator to turn the A/C clutch on or off.

6.An air grid opening is located at the lower left corner of the ATC version control panel and is labeled ATC. This air grid provides cab air temperature to the air temperature sensor for automatic temperature control of the system.

Page 20

DESCRIPTION AND OPERATION

MANUAL CONTROL PANEL

		Figure 12 — Manual Control Panel
1.	Blower Control Knob		4. Fresh/Recirc Lever
2.	Temperature Control Knob		5. A/C (On/Off) Push-Button Switch
3.	Mode Control Knob

The Manual control panel uses the following rotary control knobs, push-button switches and lever to operate the A/C system:

1.The blower rotary control knob is a five-position switch used to control the amount of air delivered through the vents.

2.The temperature rotary control knob allows the operator to adjust the temperature of the air in the cab.

3.The mode selection rotary control knob allows the operator to choose the direction of air in the cab (panel, panel/floor, floor, defrost/floor, and defrost positions).

4.The Fresh/Recirc (recirculation) lever allows the operator to choose the type of air circulating within the cab (fresh or recirculated air).

5.The A/C push-button switch allows the operator to turn the A/C clutch on or off.

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