Year 2019 Update:

The AC compressor as already documented had been repaired twice due to leaking shaft seal. This repair was successful but during the last years inefficiency was prevalent especially when idling. 

The compressor was tested using pressure gauges and it showed that during idle the service pressure was below the normal values which is probably attributed to worn piston rings. Moreover the compressor was making whining sounds which clerly showed that the end of its life had been reached.

A new AC compressor by Sanden was purchased and the exact equivalent is the SD7H13. It is a 7 piston compressor which ensures a smoother operation while keeping the same displacement and size.

You may find a video created to show the new compressor while running along with the changes in cycles of operation in the air conditioning system.