GMV5 D.C INVERTER MULTI VRF                                                                                              SERVICE MANUAL 
198 
3 KEY PARTS MAINTENANCE 
3.1 CAUTIONS ON CONTROLLER AP1 REPLACEMENT 
3.1.1 Cautions on ODU AP1 Replacement 
3.1.1.1 Distinguishing Master Module from Slave Module 
Before replacing ODU AP1, determine the module is a master ODU or a slave ODU. They can be 
distinguished based on: 
(1) ―Master module DIP state (SA8_MASTER-S)‖ 
Every cooling system has only one master module (set in power-off state). When a DIP is ―ON‖, the 
corresponding  position  is  ―0‖;  when  the  DIP  is  ―OFF‖,  the  corresponding  position  is  ―1‖.  If 
SA8_MASTER-S is set to ―00‖, it indicates a master module; if it is set to ―10‖, it indicates a slave module 
(as shown in the figure below).   
DIP setting 
position
DIP setting 
position
DIP setting 
position
DIP setting 
position
Master module state
Slave module state
 
(2) AP1 LED 
When a master module is  powered on, LED1  is displayed as  ―01‖. For a slave module, LED1 is 
displayed as ―02‖, ―03‖ or ―04‖ (as shown in the figure below).   
LED1 display state 
Master module state
LED1 display state 
Slave module state
LED1 display state 
Slave module state
LED1 display state 
Slave module state
Or
Or
 
3.1.1.2 Cautions on Replacement of Master ODU AP1 
Before replacing master module AP1, make the following preparations: 
(1) Master module DIP setting 
Set the new AP1 identical to the faulty AP1. Note that settings must be performed when the master 
ODU is powered off and they will take effect after the ODU is powered on. Settings that are performed in 
power-on state are invalid.   
(2) Communication state check