mitsubishi ac error code 4250

[mazawi]

hi guys,

I called for a fault code 4250 on mitsi city multi. i dissconnected the comp and tested the voltage to the lead and found one of the 3 test dosent match, i believe the inverter faulty. but when i rang mitsi the tech guy said i should disable the current sensor befor carrying out the test as may the comp faulty. i didnt check the comp. now do you have any other idea to test the inverter as i will go back Monday.

Thanks

[install monkey]

inverter checker- costs about £50 also prove ur getting 3phase to the condenser too

[Thermatech]

On 410a models you need to do the dip setting on inverter board to disregard low amps when you test the inverter output with compressor disconnected as Mitsubishi tech engineer advised.
Make sure to make the outdoor temp sensor warm otherwise if you have had 415v power off the outdoor unit will start in compressor warm up mode. In this case the inverter output is only on 2 phases to generate heat in the comp windings but not run the comp motor.
Make sure the compressor windings resistance & mega test to confirm windings are not to ground.