Troubleshooting Guide
Table Of Contents
- Foreword
 - Safety Notice
 - CONTENTS
 - Safety Notice on Maintenance
 - Safety Notice on Operation
 - 1. Product Introduction
 - 2. Control
- 2.1 Operation Mode
 - 2.2 Control Mode
 - 2.3 Functions
- 2.3.1 Set Capacity Dial Code
 - Set the capacity of the outdoor unit through the f
 - Capacity
 - 24K
 - 36K
 - 48K
 - 60K
 - Dial Codes
 - 2.3.2 Set Defrost Mode
 - The second digit dial code are selecting the defro
 - 2.3.3 Set Operating Mode
 - The third digit dial code and the fourth digit dia
 - By setting the Forcible mode dial codes of the con
 - Energy saving mode is achieved by setting the cond
 - 2.3.4 Set Indoor Fan Speed
 - Set the indoor fan speed through the four-digit di
 - Capacity
 - 24K indoor unit dial code
 - 36K indoor unit dial code
 - Level 1 (Default)
 - Level 2
 - Level 3
 - Capacity
 - 48K indoor unit dial code
 - 60K indoor unit dial code
 - Level 1 (Default)
 - Level 2
 - Level 3
 - 2.3.5 Forced Defrost Control
 - Press and hold "SW1" for about 5s to enter the fir
 - 2.3.6 Refrigerant Recovery Control
 - Press and hold "SW1" for about 5s to enter the fir
 - 2.3.7 Forced Operation Control
 - Press and hold "SW1" for about 5s to enter the fir
 - 2.3.8 Thermostat Functions
 - Thermostat model: XE70-00/E1, please refer to the
 
 - 3.1 Wiring Diagrams
 - 3.2 PCB Layout
 - 3.2.2 IPM, PFC Testing Method
 - 3.3 Error Code
 - 3.4 Troubleshooting
- 3.4.1 “E1” Compressor High Pressure Protection
 - 3.4.2 “E3” Compressor Low-pressure Protection, Ref
 - 3.4.3 “E4” Compressor Air Discharge High-temperatu
 - 3.4.4 “F2” Condenser Temperature Sensor Error
 - 3.4.5 “F3” Outdoor Ambient Temperature Sensor Erro
 - 3.4.6 “F4” Discharge Temperature Sensor Error
 - 3.4.7 “F6” ODU Tube Temperature Sensor Error
 - 3.4.8“EE” ODU Memory Chip Error
 - 3.4.9 “H4” Overload
 - 3.4.10 “H5” IPM Protection
 - 3.4.11 “H6” DC Fan Error
 - 3.4.12 “H7” Driver Out-of-Step Protection
 - 3.4.13 “HC” PFC Protection
 - 3.4.14 “Lc” Startup Failure
 - 3.4.15 “P0” Driver Reset Protection
 - 3.4.16 “P5” Over-Current Protection
 - 3.4.17 “P6” Master Control and Driver Communicatio
 - 3.4.18 “P7” Driver Module Sensor Error
 - 3.4.19 “P8” Driver Module High Temperature Protec
 - 3.4.20 “PA” AC Current Protection
 - 3.4.21 “Pc” Driver Current Error
 - 3.4.22 “PL” Bus Low-Voltage Protection
 - 3.4.23 “PH” Bus High-Voltage Protection
 - 3.4.24 “PU” Charge Loop Error
 - 3.4.25 “ee” Drive Memory Chip Error
 - 3.4.26 “e1” High Pressure Sensor Error
 - 3.4.27 “C4” ODU Jumper Cap Error
 
 - 3.5 Failures Not Caused by Errors
 
 - 4. Maintenance
 - Appendices
 - 1. Resistance/Temperature Lists of Temperature Sen
 - 2. Temperature/Pressure List of Refrigerant
 - 3. Operation Tools
 
MRCOOL Universal Service Manual
19
Outdoor unit:
Model: MDUO18036、MDUO18060 
Mainboard
No.
Printing
Interface
No.
Printing
Interface
1
AC-L
Live wire input
11
H-PRESS
high pressure sensor
interface
2
AC-N
Neutral wire input
12
LPP
System low pressure
protection interface
3
HEAT_TI
E_B
Chassis electric
heating belt
13
HPP
System high pressure
protection interface
4
HEAT_TI
E_C
Compressor electric
heating belt
14
T_SENSOR2
2. Outdoor tube temperature
sensor interface
4. Outdoor ambient
temperature sensor interface
6. Discharge temperature
sensor interface
5
4WAY
4-way valve
15
T_LAC
Low temperature cooling
temperature sensing










