I suspect that there are a few Mitsubishi installers/technicians floating around on this forum so I'm hoping that someone will have some helpful info on options to repair one of our outdoor units...

I have a (now obsolete) MUZ-FA35VA outdoor unit reporting an inverter over current fault - Diagnostic codes are: 5 x sequence power LED flash in the indoor unit with a 2 x sequence flash on the red inverter LED. The inverter compressor will not start. 

The outdoor fan does attempt to start every 3-5 minutes until the indoor unit stops operating and drops into fault mode.

This PCB is obsolete and not available from the factory but my electronics hobby 'fix-it' mentality tells me it should be repairable if I can find an expert tech that can locate the actual over current fault?

I am an electronics enthusiast so I understand the basic circuits and I have extensively tested the power PCB and inverter PCB in place and also powered up on my lab bench (with the reactor connected) but I cannot locate the actual faulty component.

(a) The compressor winding resistances test fine with no ground shorts.

(b) RV Coil, LEV Coil, Fan Motor, and all Thermistors are within test ohm range.

(c) 230V AC is being rectified correctly to approximately 320V DC across test points on the inverter board and expected DC voltages are routing to the IPM module correctly.

(d) The Reactor tests fine with no shorts.

(e) Testing of the live board shows correct high 300V+ DC voltages and regulated low DC voltages (e.g 13V, 5V, 12V) are arriving to all expected destination points.

(f) Diode mode tests of the IPM module (in-place) are all correct with no shorts or invalid values across the W-V-U inputs/outputs or to ground. When bench tested and powered on the expected stable 15V DC can be measured on the IPM W-V-U output.

However when the PCB is installed in the outdoor unit and indoor powered up there is no AC voltage generated on the compressor output as the inverter has dropped into the over current fault.

If anyone can recommend an electronics expert willing to have a crack at trying to fix this type of inverter board, please let me know.