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INDOOR UNIT
SERVICE MANUAL
Models
MSZ-EF09NAW -
MSZ-EF15NAW -
MSZ-EF09NAB -
MSZ-EF15NAB -
MSZ-EF09NAS -
MSZ-EF15NAS -
MSZ-EF12NAW -
U1
MSZ-EF18NAW -
U1
MSZ-EF12NAB -
U1
MSZ-EF18NAB -
U1
MSZ-EF12NAS -
U1
MSZ-EF18NAS -
U1
Outdoor unit service manual
MXZ- ∙C∙NA(HZ) Series (OCH573)
CONTENTS
1. TECHNICAL CHANGES ······························2
2. PART NAMES AND FUNCTIONS ··················3
3. SPECIFICATION ········································4
4. OUTLINES AND DIMENSIONS ·····················6
5. WIRING DIAGRAM ·····································7
6. REFRIGERANT SYSTEM DIAGRAM ·············8
7. SERVICE FUNCTIONS ································9
8. MICROPROCESSOR CONTROL ················ 11
9. TROUBLESHOOTING ······························· 19
10. DISASSEMBLY INSTRUCTIONS ················· 31
PARTS CATALOG (OBB736)
Revision A:
• 4. OUTLINES AND DIMENTIONS has been
modified.
• Some descriptions have been modified.
OBH736 is void.
No. OBH736
REVISED EDITION-A
U1
U1
U1
U1
U1
U1

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Table of Contents
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Summarization of Contents

Part Names and Functions
Accessories List
Lists included accessories for the specified indoor unit models.
Specification
Operating Range
Details operational limits for cooling and heating modes based on ambient conditions.
Outlet Air Speed and Coverage
Specifies airflow rates and air coverage distances for various models and modes.
Service Functions
Timer Short Mode
Shortens ON/OFF timer set times for service purposes, reducing delay.
Remote Controller Pairing
Describes pairing remote controllers with specific indoor units for exclusive control.
Auto Restart Function
Explains automatic operation resumption after power interruption based on memory.
Microprocessor Control
Wireless Remote Controller Overview
Details the functions and buttons of the wireless remote controller for unit operation.
Indoor Unit Display Section
Explains the meaning of the operation indicator lamp on the indoor unit.
Cool Operation
Describes the procedure and features of the unit's cooling operation mode.
Dry Operation
Describes the procedure and features of the unit's dehumidification (dry) operation.
Fan Operation
Describes the procedure and features of the fan-only operation mode.
Heat Operation
Describes the procedure and features of the unit's heating operation mode.
Auto Changeover Operation
Explains automatic switching between cooling and heating modes based on room temperature.
Auto Vane Operation
Details the control and modes of the horizontal vane for air direction.
Timer Operation
Guides on setting and using ON/OFF and program timers for scheduled operation.
Weekly Timer Operation
Explains how to set and manage weekly timer schedules for automated operation.
Smart Set Operation
Describes the procedure for setting and using smart operation modes for optimized comfort.
Emergency and Test Operation
Details the emergency operation and test run modes for servicing and troubleshooting.
Time Delay Operation
Explains the 3-minute time delay function for compressor protection.
Temperature Unit Conversion
Instructions for switching the temperature display between Fahrenheit and Celsius.
Troubleshooting
Troubleshooting Cautions
Important safety and preparatory steps before performing troubleshooting.
Remote Controller Battery Replacement
Procedure for replacing weak or dead batteries in the remote controller.
Failure Mode Recall Function
How to recall stored error codes and abnormal conditions from the unit's memory.
Indoor Unit Failure Mode Table
Maps indicator lamp blinking patterns to specific indoor unit failures and remedies.
Troubleshooting Instruction Flowchart
A flowchart guiding the diagnosis of unit malfunctions and operational issues.
Troubleshooting Check Table
Table of symptoms, conditions, and remedies for common air conditioner problems.
Main Parts Troubleshooting Criteria
Criteria for checking key components like thermistors, motors, and PC boards.
Troubleshooting Flow for Specific Issues
Detailed step-by-step troubleshooting procedures for various scenarios.
Remote Controller and Receiver Troubleshooting
Diagnosing issues related to the remote controller and its indoor receiver.
Indoor PC Board and Fan Motor Troubleshooting
Diagnosing issues with the indoor PC board, fan motor, and related components.
Miswiring and Serial Signal Error Check
Procedures for checking wiring integrity and communication errors between units.
Electromagnetic Noise Troubleshooting
Guidance on preventing and resolving electromagnetic interference with external devices.
Test Point Diagram and Voltage Specifications
Provides electrical test points and voltage specifications for diagnostic purposes.
Disassembly Instructions
Panel Removal
Step-by-step guide to safely removing the front panel of the indoor unit.
Indoor Electrical Box Removal
Instructions for detaching and removing the indoor unit's electrical box.
Internal Board Removal
Detailed steps for removing the power board, display, receiver, and control boards.
Nozzle Assembly Removal
Instructions for carefully removing the indoor unit's nozzle assembly.
Horizontal Vane Motor Removal
Procedure for detaching and removing the horizontal vane motor unit.
Fan Motor and Coil Thermistor Removal
Steps for removing the indoor fan motor, its band, and the coil thermistor.
Indoor Coil Thermistor Fixing
Method for properly fixing the indoor coil thermistor to the heat exchanger.

Table of Contents