unix-freak wrote:
I forgot to mention that the condensing unit is under a deck with 3
feet of clearance above it. I've heard from some that it's ok, and
from others that it's not.

Trane's installation guide for their current upflow models (XB10,
XB1000, XR12) says you need 5 feet unrestricted above the top of the
unit. Of course this doesn't apply to the side-exhaust models. Since
yours is an older unit it is probably top exhaust and therefore the 5
feet recommendation probably applies.

Wheter that is the cause of your low drop across the evaporator or
whether it is something else (like a restriction in the liquid line, bad
compressor valves, etc.) we can't tell from here.