View Full Version : Mitsubishi 'UF' fault code

23-07-2014, 09:54 PM
I have been working on a Mitsubishi PUHZ-RP125YHA2 cassette system today, original fault on the unit was a P5 fault which I traced to a blocked drain and very dirty tank pump. Cleared the problem which seemed to clear the P5 fault, when the unit seemed to be running ok I checked on it before leaving site and the fault had switched to a UF fault.

I know that this has something to do with compressor overcurrent/compressor lock, the unit seemed to run fine after the drain was cleared. I isolated the indoor unit by the isolator on the unit and when I switched it back on it came up with E9 I think which was communication between indoor and out door. I couldn't get this fault to clear so isolated both units by their isolators, switched on outdoor then indoor and that fault cleared and unit seemed ok but then decided to through up this UF fault.

I have checked the outdoor unit and watched it try and run but the compressor seems to try and run then shuts down again either as if trying to switch to run but cant or there isn't enough power feeding the compressor so it is shutting itself down.

I don't work too much with Mitsubishis of this type so am a bit stumped, could just do with some ideas of what to look for etc. I have tested terminals on the compressor and they all look good but with there being like 4 boards on the unit and no wiring diagram it would be great to have an idea of what could be causing the compressor to run intermittently like it is doing.

I have also tested one of the capacitors (which tests good) but am unable to get to the two in behind the vertical control board to test those as I thought it could be one of them not supply enough of a kick??