Several weeks ago I followed the failed maintenance supers's(several guys) attempts to fix a no cool. I found contaminated R-22 and a TXV installed with the piston still installed. The bulb was also not secured to the piping, nor was it touching anything, just sitting in the air stream. I removed the TXV, pulled a good vacuum and charged the system with new R-22, problem fixed.
Returned to the same property last week, different apartment. This system showed low on Freon, I don't remember the exact numbers but the SH was high and the Subcool was low. It also had a TXV, also not secured to anything just floating around the air stream. I didn't pump down and check for a piston. The pressures did change however when I held the bulb in my hand. I added Freon and left the Subcool at 10. They haven't called back saying it isn't working, but it's created a question in my mind.
These are old Suntherm units, Heat pump. A coil, the bulb jammed between the cover panel and the U bends at the edge of the coil, so not really out in the middle of the air stream.
The question is; Does a TXV bulb always have to be in contact with the piping? What will happen if it isn't? I did notice that when I added R-22, High side would shoot up very quickly, then slowly fall and stabilize.