Came to a unit today a Mitsubishi PUHZ P125VHA switched on at the controller but no cooling. Checked the filters wich were blocked but still no cooling. Looked at the controller again and i had a UF fault ( compressor lock)
Checked the condensor, the condensor fans would come on for 10 seconds then go off for 10 seconds then come on for 10 seconds then go offf again etc etc. Found the compressor stone cold. Disconnected the terminals to the compressor and checked the compressor for down to earth and also the resistance across the windings- both came back ok.
Decided to use my Daikin inverter checker. I connected the compressor leads to the checker then switched the outdoor unit on forced cooling. On the inverter checker 1,4 and 6 lit up for a few seconds then all 6 lit up for a second or so then1,4 and 6 lit up again then 3,4,5 and 6 lit up then finally all 6 lit up. I spoke to daikin about this and they said they dont know what the lights on the checker mean on a mitsubishi unit as they can only speak for daikin. So i rang mitsubishi up and they said they havent used that sort of inverter checker and couldnt advise what the lights mean???

I ended up measuring the voltage to each phase as it goes onto the compressor but with it disconnected and got 80volts for each phase, which would be enough to start the compressor as its an inverter but the compressor wont start.

I thought that because its been cold the liquid may have migrated back to the compressor and caused the compressor to lock due to liquid inside. I left power to the condensor but switched the controller off, which should give the compressor around 20v on each terminal and this acts as a crank case heater but i was getting 80v constantly instead of around 20 even with the controller off and the forced cooling dip switch back to normal.
Any ideas guys?