Hello all pro here,

I have a heat pump unit and the thermostas came with it does not work
any more (I think or could be something wrong with the unit itself), I
replaced with new one, and it worked for couple day than cold air did
not come out any more, even when I swithed FAN to ON position. I had to
turn the unit off for a while then turned it back on and it worked a
short time and no cold air again, what could it be wrong?, thanks in
advance.

It is HOT where I live, .