Sounds like a posibility but this happens in no logical order. The thing could be off for days and demand be in this no pressure mode, then is a short sometimes long time it run great. The compressor is down in the unit so right now looking for the label is a no go but I did have the old compressor sitting in the garage. Label on it was ZPS51K4E-PFV-230-ZSM
Leaving pressure gauges out of the picture, the unit in heating mode does not make the suction line hot! Sound of the compressor is harsh, sometimes it will stay that way for 5, 10, 15 mins before compressor smooth out to quite normal sound, suction line is now hot. the same process can be seen in cooling mode or defrost, if the compressor goes into the "quite" stage the deforst will produce steam, if it stays in the noisy mode no steam and no defrost.