Gree                GMV6 DC Inverter VRF Units Service Manual 
 
If there is no refrigerant in the system or the amount of refrigerant does not meet the requirements 
for starting operation, the unit will display U4 “Refrigerant-lacking protection”, as shown below. The unit 
will enter into the next step. At this time, it is necessary to check whether there is a leak or charge some 
refrigerant until the abnormality is eliminated. 
—
Meaning 
Progress 
Code 
Display 
Code 
Display 
Code
Display 
09_refrigerant 
judgement before 
startup 
db  ON  09  ON  U4  ON 
The refrigerant in the system is 
insufficient. Please charge 
refrigerant until the fault 
Step 13:
 Unit debugging step 10 is “status judgment of main pipeline before starting”. 
If the main module displays as below, it indicates the unit is starting the operation for judgment. 
—
 
Debugging code  Progress code  Status code   
Meaning 
Progress 
Code 
Display 
Code 
Display 
Code 
Display 
main pipeline before 
db  ON  10  ON  ON  ON  Starting and operating. 
If the unit has detected the abnormal status, the display is as below:   
—
 
Meaning 
Progress 
Code 
Display 
Code 
Display 
Code 
Display 
main pipeline before 
db  ON  10  ON  U6  ON  Main pipeline is abnormal. 
At this time, it is necessary to check whether the gas valve and the liquid valve are completely open 
or whether the main pipeline is blocked. Once inspection is completed, you can return to the previous 
step by pressing SW4 button to re-enter the judgment. 
If inspection valve of the unit is normal, the display is as below. The unit will automatically enter into 
the next step.   
—
 
Meaning 
Progress 
Code 
Display 
Code 
Display 
Code 
Display 
main pipeline before 
db  ON  10  ON  OC  ON 
The main pipeline is turned on 
normally. 
Step 14:
 Unit debugging step 11 is “reserved function”. 
The main module display is as below. The unit automatically enters into the next step.   
—
 
Meaning 
Progress 
Code 
Display 
Display 
Code 
Display 
—
 
Step 15:
 Unit debugging step 12 is “reserved function”.   
The master module display is as below. Then the unit automatically enters into the next step.