I realize this post is very old, but just recently a few weeks ago, I changed three thermostats on three True back-bar (TBB model) coolers: IN ONE DAY!! Not sure why True t-stats always seem to get erratic and freeze product. When I replace, first customer removes all product. Then I replace t-stat. I don't reinstall in the copper tube in the evaporator. On this particular model, I drop the evap cover enough to get to the front of the evaporator, the insert the A12-700 capillary directly into the evaporator coil (after either folding it up, or coiling it up into a pretty little pigtail.)
In the last 2 days I have also replaced three True thermostats with A12-700's, but they have been upright Reachins (t-49, t-19, gdm-49). Tried installing in the copper tube, and it seems somehow, the copper tube "insulates" the capillary and slows down the response a lot. So it the box would get too cold (~30*f), cycle off, then not cycle on until too warm (~42*f). It responds much better folded or coiled up and installed directly into the fins: consistent 37*f cut-in, 33*f cut-out (box temperatures, not evap temps). AND it's a lot easier to install them this way. I think from now on I will always do it this way.
I remember reading a post about the copper tube on True's breaking loose so they don't make good contact, and this causes issues. Or as my service manager says "Yeah, True t-stats suck."