I work at an apartment complex that still has some of the original units (43 years old) and the most common major problem is the txv on the indoor coil. Since they are a pain in the butt to change (tight and hidden), i usually replace the whole unit. The txv is tight , but if i could find a flowrater it would be easy to replace. Now can someone tell me where i can find the assembly (shell and piston with compression fittings). Ive seen them before but don't know where to get them, ive already tried Johnstone. Please help