R410A All DC Inverter V5 X Series 50Hz      MCAC-VTSM-2015-10 
156 Troubleshooting 
If the value is not in the range, this indicates a problem with the electrolytic capacitor power supply, check the 
power supply for high or unstable voltage. 
If the voltage value is normal, then the main PCB has malfunctioned, it needs to be replaced. 
4)  L8/L9 troubleshooting 
Step 1: Compressor check 
Measure the resistance between each two of U, V, W terminals of the compressor, all the resistance should be 
the same and equal to 0.9~5 Ohms. (Fig. A and Fig. B) 
Measure  the  resistance  between  each  U,  V,  W  terminal  of  the  compressor  and  ground  (Fig.  C),  all  the 
resistance should be infinite (Fig. D), if not the compressor has malfunctioned and needs to be replaced. 
If the resistance values are normal, then go to step 2. 
Step 2: Disconncet the power wiring from the compressor(named compressor A) of the faulted system(named 
system A). 
If there is a system running normally nearby (named system B): 
Extend the power line of the inverter compressor of system B, connect compressor A to the control box of 
system B, make sure that the U, V, W terminals are connected in right order, then start system B.     
If  compressor  A  can  start  normally,  that  means  compressor  is  OK,  the  control  box  of  system  A  has 
malfunctioned, then replace the main PCB of system A and ensure correct wiring. 
If compressor A can not start normally, that means compressor A is damaged and needs to be replaced.   
If there is no normal system nearby: 
Replace the main PCB of system A and ensure correct wiring, if compressor A can start normally, it means the 
main PCB which was replaced was damaged. If compressor A still can’t start normally, replace the compressor. 
   
Power line (U, V, W terminal) 
Connect compressor A 
to the control box of a 
normal system B, 
check whether 
compressor A can start 
normally