Unit Details: Model REYQ16M8W1B

Original call out was system not working. On arrival found system main breaker tripped and inverter board had failed.

Checked inverter compressor windings resistance checks and insulation test, all ok.

Replaced the inverter board, on system trying to run the inverter compressor the inverter is energised and provides voltage to the compressor, a whining noise can be heard at the compressor, approx. 1.4amp at each phase is measured. The power from the inverter then drops off and the process starts again. The compressor will not run. Suspected compressor seized so replaced inverter compressor.

With new inverter compressor installed and new inverter board installed, commissioned system, once again, on inverter board energising , a whining noise can be heard at the compressor, again, approx. 1.4amp at each phase is measured. The power from the inverter then drops off and the process starts again ( approx. 30 seconds later). The compressor will not run.

Performed various tests:

Inverter - Power transistor check mode performed
Fan Motor – resistance values checked all ok.
Noise Filter – voltage output
Contactor K1M working
Output from all boards correct

With all checks performed compressor is still not operating ( again, inverter board energising, providing voltage to compressor, whining noise can be heard then power drops off).

To be sure all components are working, we have an identical system on the site, so I have swapped boards with this system.

Unit with the compressor not working now has the working units noise filter, fan motor PCB, fan motor and inverter board – compressor still not running.

Unit that was working now has failed units noise filter, fan motor PCB, fan motor and inverter board installed, system all working well – thus none of the boards/fan are causing this issue.

I have not replaced the main PCB with all the sensors connected to date.

The technical team seem to think I have been provided with a faulty compressor, but I am not so sure, especially as it seems to be doing exactly the same as the original compressor, am I missing something that could be holding this compressor off?

Additional Notes:
The inverter compressor has 4 cable connections, the fourth being the N connection that I believe is used to measure the compressor rotation.

No fault codes are being providing by the system.

The new inverter board that was fitted with the old inverter compressor has been tested on the other system and works

Any help would be appreciated.