It is best to test inverters with no compressors connected especially if you expect the compressor is at fault. But if you remove the wires from the compressor and try to run the systems a fault will be displayed the fault is caused by the inverter PCB being able to detect whether a compressor is connected or not. Most modern inverters are able to detect whether the compressor has been disconnected in only a few seconds making testing very difficult.
Testing can be done in two ways:
Firstly the hard way……
You will need a digital multi meter with a min max function,
Turn off the power
Disconnect the compressor either from the PCB or at the compressor terminals. Connect your meter to two of the phases (Red to blue) set your meter to record max and min voltage
Power up and Start the unit Let the inverter start and watch the Voltage rise. Record the maximum Voltage. The inverter will stop after a few seconds and the voltage will fall to 0. Swap the leads to measure the next two phases (Red to Yellow). Measure as before Repeat for the last two phases Blue to Yellow. The readings of maximum voltage should be the same for all 3 measurements if not the inverter is faulty, the PCB will need replacing.
If the readings are equal the Inverter is healthy and the compressor will need replacing.
And the easy way......
You will need an Inverter tester, Turn off the power. Disconnect the compressor lead from the compressor terminals. Connect your inverter tester to all 3 leads (polarity is not important) Power up and Start the unit. Let the inverter start and watch the LED's.
All 6 must light up and should be of equal brightness
The inverter will stop after a few seconds and the LED's will go out
If you miss the LED's (they will only light for a couple of seconds) the unit will try to start again 3 times with a 3 minute delay between each test
If all 6 LED's DON’T light up the inverter is faulty, the PCB will need replacing.
If the LED's all light up the Inverter is healthy and the compressor will need replacing.