Split variable speed Lennox heat pump (details available upon request), was struggling to get the air going hot enough as the ambient temperature was dropping to about +5C (41F), as if it was its balance point. Eventually, gave up the ghost one night and just started blowing cold air.
Contractor came, declared TXV dead. Ordered, replaced Friday morning. Supply air around 96F with the ambient in low 50s.
Come 3AM Sunday, the unit started dying, and by 9AM was dead again, with the same symptoms.
Contractor came again yesterday evening, couldn't find anything more, noted that there appears to be a restriction in the system, but couldn't identify what it is. Also noted that the pressures are jumping erratically. Expressed concern about reversing valve.
After a while, the system stabilized with the supply air being just about the same 96F and the ambient being again in low 50s.
1AM, the unit is dead. The last breath was - supply temperature rose to 80F within about two minutes, then quickly dropped back to return temperature.
Contractor decided to give up and call for second opinion; waiting.
Any clue from distinguished audience here?