I've already posted two questions about heat pumps this weekend,
so I know I'm pushing my luck, perhaps squeezing the good-nature
of the helpful forum veterans. Sorry, but this one may save some
more pain.

We have a Trane heat pump. Major compressor burnout.
The thing even blew a hole through one of the electrical
terminals at the compressor. Very stinky.

Compressor was changed. Evap coil was changed. It had
a big leak and a bunch of fins were dissolved--nobody
really can figure that one out.

Changed the compressor, of course. As stated in earlier
post, little filter-drier was removed and big blue 163S was
put on the liquid line. Much, much purging with nitrogen.
Used the acid-neutralizer stuff for good measure and
superstition.

Put on gauges, start unit in cooling. Gauges don't budge.
Check reversing valve. 24 V at wires to solenoid.
Remove wires. Add. Remove. Add. Rap on reversing valve
body with large crescent. Clicks but no wooshing.
Three of the four reversing valve appendages were
very warm. Fourth closer to ambient of maybe 53 F.
Based on my assumption that a max of two appendages
should be warm, I concluded the reversing valve is bad.
We will schedule a replacement pursuant to senior tech
approval.

My question is whether even with such major reversing
valve failure, could THAT account for the gauges not budging
the needles, or should we also suspect check valves are
stuck open? (In case you haven't seen my recent posts,
you should know that I don't have experience with
such problems on heat pumps, that I'm only going
with what I've read.)

One more possibly relevant point. The outside unit has
a TXV. When we changed the inside coil, we noted it did
NOT, absolutely, no mistake, did NOT have an orifice.
The coil installation instructions and Trane Help-line both
said it SHOULD have an orifice and specified its location.
We obtained and installed the orifice. Senior tech
said he did not know how it could have functioned without
an orifice. We did not ever observe operation of the unit
prior to the burnout, so we can't say how it functioned,
good or bad.

Is the reversing valve replacement likely to bring total success?
Thank you all.