Check incoming voltage with voltmeter. Between L1 to L2, it should be between 187 and 253 Volts AC. If voltage is outside of these parameters, that will need to be corrected first. A mini split voltage monitor is recommended, especially when the location has higher voltage.
The IPM has two main parts:
Bridge rectifier which converts AC to DC voltage
Insulated Gate Bipolar Transistors (IGBT)
Remove the unit cover and control box cover, then restore power to the unit.
Check for DC voltage at terminals P+ and N-, at the capacitors:
Should be around 300 volts +/–
If there is no voltage, the rectifier is bad and you should replace the IPM
On smaller units the IPM is part of the Main PCB
Moving on to test the IGBT, first disconnect the power from the unit and allow 5 minutes for the capacitors to discharge before beginning this test.
Failure to do so may cause system damage or cause electrical shock!
To test IGBT set your meter on Mega ohms. Place one lead on the P+ terminal, at the capacitor.
Place the other lead on:
U and record your reading
V and record your reading
W and record your reading
Take the lead off of the P+ terminal and put it on the N- terminal.
Place the other lead on:
U and record your reading
V and record your reading
W and record your reading
Are these readings close and consistent? If so, the IPM checks out; if not, replace the IPM.
If the IPM is good, other options to test include:
Fan motor
Compressor
Check the Compressor jacket for discoloration or burn markings, this can be an indication of overheating
