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:

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.

• 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 leds.

• All 6 must light up and should be of equal brightness

• The inverter will stop after a few seconds and the leds will go out

• If you miss the leds (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 leds DON’T light up the inverter is faulty, the PCB will need replacing.

• If the leds all light up the Inverter is healthy and the compressor will need replacing.